CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Patent Application Serial No.

13/209,136, filed 12 August 2011 and entitled "METHOD AND APPARATUS FOR THERMAL CONTROL OF A MULTIPLE CHAMBER TEST SYSTEM," which is a continuation-in-part of U.S. Patent Application Serial No. 12/896,254, filed 1 October 2010 and entitled "METHOD AND APPARATUS FOR THERMAL CONTROL OF A MULTIPLE CHAMBER TEST SYSTEM." This application also claims priority to U.S. Patent Application Serial No.

12/896,245, filed 1 October, 2010 and entitled "TEST SYSTEM WITH VIBRATION TABLE." The entire disclosures of the above-identified applications are hereby incorporated herein by reference.

BACKGROUND

[0002] Systems for performing highly accelerated life testing (HALT), highly accelerated stress screening (HASS), and highly accelerated stress audits (HASA) are available to test the reliability and durability of manufactured products. More particularly, the durability of products can be tested using HALT systems and procedures. Products can also be tested for defects before they are distributed to consumers using HASS procedures, where all of the products are tested, or HASA procedures, in which samples taken from a production run are tested. In general, such testing includes subjecting devices under test to vibration energy and/or temperature cycling. Such stresses may be introduced to a device under test by mounting the device under test to a shaker or vibration table that is located inside an environmentally controlled test chamber.

SUMMARY

[0003] In connection with HASS and HASA programs, including HASS and HASA programs that utilize multiaxis random vibration combined with rapid (greater than 40 C per minute) changes, the following systems are capable of efficiently testing a large number of products. Test chambers are disclosed that permit access to the vibration tables from multiple sides, facilitating placement of products under test in the test chamber, and the interconnection of the products under test to the vibration table. Unlike the prior art, where vibration tables have large area that is difficult to access (and thus rarely used to support a product under test), the systems disclosed herein operate to increase test chamber throughput, with the result that the cost per unit tested is lower than it would otherwise be. In these systems, the vibration table surface is sized for high utilization of space, thereby reducing, as compared to the prior art, the surrounding chamber size and improving energy efficiency during thermal cycling.

[0004] In one embodiment, a product testing system has a plurality of vibration tables controllable to vibrate product mounted with the vibration tables; and an air circulator for controlling air temperature of air surrounding the product.

[0005] In one embodiment, a vibration table takes the form of a vibration tray that can be removed from the product testing system. The vibration tray includes a table top upon which fixturing couples product to the table top. The table top may be selectively affixed to mating structure within the product testing system and then actuated to function as the vibration table therein. The table top may be selectively removed from the mating structure to facilitate coupling and decoupling of product to the table top.

[0006] In one embodiment, a product testing controller is provided and includes: means for controlling vibration of a plurality of vibration tables in a common cabinet; and means for controlling air temperature surrounding product mounted on the vibration tables.

[0007] In one embodiment, an environmentally sealable product test chamber is provided. A vibration table is configured for mounting product thereto. One or more vibration actuators are responsive to drive signals to vibrate the vibration table. The chamber may be selectively affixed within the product testing system generating the drive signals and controlled air temperature for the chamber. The chamber may be selectively removed from the product testing system to facilitate coupling and decoupling of product to the vibration table.

[0008] In an embodiment, a method for testing a plurality of products is provided, including: vibrating at least one first product on a first vibration table within a cabinet;

simultaneously vibrating at least one second product on a second vibration table within the cabinet; and simultaneously controlling air temperature within the cabinet and surrounding products on the first and second vibration tables.

[0009] In accordance with certain embodiments of the present disclosure, a product testing system with multiple chambers or compartments are provided. More particularly, multiple test chambers or volumes, each associated with a vibration table, are provided within a single cabinet (sometimes denoted as "enclosure" herein), for testing multiple devices or products, referred to herein as devices under test, simultaneously. Each test chamber within the enclosure is provided with temperature controlled air from a plenum. In addition, for embodiments in which air powered actuators or hammers are employed, a table air enclosure can be included to prevent the actuator exhaust air from mixing with the temperature controlled chamber air. [0010] In order to provide same or similar thermal conditions in each of the multiple chambers, various features have been developed and incorporated into the plenum design. For example, in an intake plenum portion of the air handling system, heating and/or cooling elements are disposed. Air is drawn through the intake plenum, across the heating and/or cooling elements, by one or more fans. In accordance with certain embodiments of the present disclosure, the fan is of a tangential blower type design. Moreover, the fan can have a width that is equal or about equal to the width of the plenum assembly or a portion of the plenum assembly. The air output by the fan is passed to an outlet portion of the plenum assembly or outlet plenum. Where the plenum assembly provides air to multiple test chambers that are stacked vertically, the outlet plenum can be tapered or staggered, such that the area of the plenum decreases with increasing distance from the fan. In accordance with still other embodiments of the present disclosure, one or more flow control devices can be included. More particularly, a flow control device or element can be disposed within or in communication with the outlet plenum, to facilitate a balanced distribution of air to the multiple test chambers. Moreover, a flow control device can comprise a diverter, a damper, a valve, a louver, an air vane or other structure or device for controlling a rate or direction of air flow. In accordance with other embodiments, the effect of a flow control device can be varied, to control the air flow from the outlet plenum to a test chamber associated with the flow control device. In accordance with still other

embodiments, where pneumatic actuators are employed to operate the vibration tables, enclosures can be provided to keep the exhaust from the pneumatic actuators separate from the temperature controlled chamber air that occupies the test area of the chambers.

[0011] In accordance with certain embodiments of the present disclosure, multiple test chambers can be disposed in columns. In accordance with such embodiments, each column can be associated with dedicated air circulator components. For example, each column of test chambers can be associated with one or more heating elements, one or more cooling elements, one or more fans, and an outlet plenum. Moreover, air circulator components associated with particular test chambers or columns of test chambers can be controlled independently of the air circulator components of other test chambers or columns of test chambers, thereby increasing flexibility and usage of the product testing system. In accordance with still other embodiments, flow control devices associated with individual test chambers or sets of test chambers can be separately controlled.

[0012] Methods in accordance with certain embodiments of the present disclosure include equally distributing air to the plurality of chambers of the product testing system. This can include controlling the air distributed to the different chambers such that the rate of air blown within each chamber is equal or substantially equal. In accordance with still other embodiments, the establishment or maintenance of thermal uniformity can include providing different chambers with air from a plenum at different rates. In accordance with further embodiments, the method can include varying the rate at which air is supplied to one or more of the test chambers. In addition, air from sources other than a thermally controlled plenum can be segregated, to prevent that air from influencing the thermal conditions within the test area of the multiple chambers.

[0013] In accordance with further embodiments of the present disclosure, methods can include independently controlling air distribution to different chambers of the product testing system or to groups of chambers within the system. For example, where the system has multiple columns of test chambers, the heating elements, cooling elements, or fans may be controlled separately for each column. As a further example, flow control devices, including but not limited to active flow control devices associated with individual test chambers can be controlled separately. For example, a flow control device for a test chamber can be operated independently of flow control devices for other test chambers in the same or different columns of test chambers.

[0014] Additional features and advantages of embodiments within the scope of the present disclosure will become more readily apparent from the following discussion, particularly when taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] FIG. 1 is a front perspective view of a product testing system, in accordance with an embodiment.

[0016] FIG. 2 is a front perspective view of a product testing system, with the front doors open, in accordance with an embodiment.

[0017] FIG. 3 is a cross-section side elevation view of portions of a product testing system depicting some of the features of an air circulator, in accordance with an embodiment.

[0018] FIG. 4A is a front elevation view of portions of a product testing system depicting some of the features of an air circulator, in accordance with an embodiment.

[0019] FIG. 4B is a front elevation view of portions of a product testing system depicting some of the features of an air circulator, in accordance with an embodiment.

[0020] FIG. 4C is a schematic front elevation view of vibration table assemblies in a product testing system, in accordance with an embodiment.

[0021] FIG. 4D is a schematic front elevation view of vibration table assemblies in a product testing system, in accordance with an embodiment.

[0022] FIG. 4E is a schematic front elevation view of a product testing system having a removable column of chambers, in accordance with an embodiment. [0023] FIG. 4F is a schematic front elevation view of the product testing system of FIG. 4E, with the removable column of chambers removed and replaced with a product rack, in accordance with an embodiment.

[0024] FIG. 5A is a bottom perspective view of portions of a vibration table assembly, in accordance with an embodiment.

[0025] FIG. 5B is a bottom plan view of portions of a vibration table assembly, in accordance with an embodiment.

[0026] FIG. 5C is a top plan view of portions of a vibration table assembly, in accordance with an embodiment.

[0027] FIG. 5D is a front elevation view of portions of a vibration table assembly, including vibration table support elements, in accordance with an embodiment.

[0028] FIG. 5E is a side elevation view of portions of a vibration table assembly, including vibration table support elements, in accordance with an embodiment.

[0029] FIG. 5F shows a frame configured to couple with an airtight fixture tray upon which product may be mounted, in accordance with an embodiment.

[0030] FIG. 5G schematically illustrates along line 5G-5G of FIG. 5F, how a fixture tray completes a seal with a frame, and illustrates fixturing that can be utilized to mount product for testing within a product testing system, in accordance with an embodiment.

[0031] FIG. 6A is a block diagram depicting components of a product testing system, in accordance with an embodiment.

[0032] FIG. 6B schematically shows a product test system including one control subsystem that controls table actuation subsystems and air circulators in multiple cabinets, in accordance with an embodiment.

[0033] FIG. 7 is a flowchart depicting aspects of the operation of a product testing system, in accordance with an embodiment.

[0034] FIG. 8 is a block diagram depicting components of a product testing system, in accordance with an embodiment.

[0035] FIG. 9 illustrates an air outlet, in accordance with an embodiment.

[0036] FIG. 10 illustrates an air outlet, in accordance with an embodiment.

[0037] FIG. 1 1 is a schematic diagram of the product testing system of FIGs. 1, 2, 3, 4A through 4F, 6A, 6B and 8 illustrating further detail providing exemplary temperature control, in accordance with an embodiment. [0038] FIGs. 12 -18 are flowcharts illustrating one exemplary method for controlling temperature within the test chamber of FIGs. 1, 2, 3, 4A through 4F, 6A, 6B and 8, in accordance with an embodiment.

[0039] FIG. 19 is a graph of temperature against time with a solid line representing a desired temperature for the test chamber of FIGs. 1, 2, 3, 4A through 4F, 6A, 6B and 8 as defined within a desired profile of FIG. 11 and a dotted line representing a measured temperature of the test chamber, in accordance with an embodiment.

[0040] FIG. 20 is a graph of temperature against time with a solid line representing a desired temperature for the test chamber of FIGs. 1, 2, 3, 4A through 4F, 6A, 6B and 8 as shown in FIG. 19 and a dotted line representing a measured temperature of the test chamber controlled using an adjusted profile of FIG. 11, in accordance with an embodiment.

DETAILED DESCRIPTION

[0041] FIG. 1 is a front perspective view of a product testing system 100 that includes a cabinet or enclosure 104 having multiple individual test chambers 108. In the example shown, six test chambers 108 are included in cabinet 104 and in system 100. However, any plurality of chambers 108 may be included within system 100 without departing from the scope hereof; furthermore, such chambers may be in a single cabinet 104 or multiple cabinets 104 (as discussed below in connection with FIG. 6B). In accordance with an exemplary embodiment, each individual test chamber 108 includes a vibration table, and a thermally controlled environment suitable for performing reliability, durability, and/or defect testing of products. Although FIG. 1 shows test chambers 108 as being similar in size and shape, it is contemplated that test chambers of different sizes and/or shapes may be included in system 100 without departing from the scope hereof.

[0042] FIG. 2 illustrates product testing system 100 of FIG. 1 with access doors 204 opened, to provide access to each of test chambers 108. With doors 204 open, some of the components of test chambers 108 can be seen in this embodiment. In particular, each test chamber 108 in the FIG. 2 embodiment includes a shaker or vibration table assembly 208. Each vibration table assembly 208 generally includes a vibration table 212 having a mounting side or surface 214 that includes mounting points 216 to which product to be tested can be connected, either directly, or through one or more fixtures. Although vibration tables 212 are shown as rectangular in FIG. 2, vibration tables may be curved, shaped or weighted in order to vary frequency response of the table when actuated, as for example shown and described below in connection with FIGs. 5A-5G. [0043] Each vibration table assembly 208 can be associated with a skirt 220 that, together with a vibration table shroud 224 (shown in FIG. 3), side walls 228 and center walls 230 defining a lateral extent of test chambers 108, enclose the actuators and supports (not shown in FIG. 2; see FIGs. 5A - 5G) associated with vibration table assembly 208. This allows the climate controlled air in test chamber 108 to be maintained separately from the actuators. For example, actuators of vibration table assembly 208 can thus be contained in an environment that is separated from the chamber air provided to test chambers 108 in which devices under test are placed and are subjected to thermal cycling and/or thermal control. As a further example, for systems 100 in which pneumatic actuators are used, by enclosing the actuators associated with each table assembly 208 exhaust air from the pneumatic actuators associated with vibration table assemblies 208 can be prevented from mixing with the chamber air provided to test chambers 108. Skirt 220 may attach with side walls 228, center walls 230, vibration table shroud 224 and/or vibration tables 212 with fasteners such as screws, or may fit into slots formed by the side and center walls, shroud and/or tables to form a labyrinth seal.

[0044] FIG. 2 shows an embodiment of components associated with an air circulator 232 of product testing system 100. In the FIG. 2 embodiment, air circulator 232 includes at least one air intake 236. Moreover, for each test chamber 108 included in a system 100, the volume associated with a test chamber 108 is in communication with at least one such intake 236. In the example system 100 shown in FIG. 2, there is one air intake 236 for each column of three test chambers 108. The air circulator 232 additionally includes an intake plenum 240. The intake plenum 240 receives air through the air intake or intakes 236, and can house or otherwise be in communication with an air circulation fan 304 (see FIG. 3).

[0045] FIG. 3 illustrates a cross-section of a system 100 in an embodiment, and in particular shows features of air circulator 232. In general, temperature controlled chamber air is circulated through the multiple test chambers 108 by air circulator 232. In operation, air is drawn into an intake plenum 240, through an air intake 236 within system 100, by a fan 304. Fan 304 may be, for example, a tangential blower or a centrifugal fan; furthermore, multiple fans 304 may be provided. As shown in FIG. 3, intake plenum 240 houses thermal control elements 306, each of which may include a heating device 308 and/or a cooling device 312. By way of example, heating device 308 is an electric resistance heating element and cooling device 312 is a cooling system that may utilize a cryogenic liquid (e.g., liquid nitrogen or other cryogenic liquid) and/or a compressed gas that cools upon decompression (e.g., carbon dioxide). Alternatively, cooling device 312 is an evaporator plate or coils of a mechanical refrigeration unit. In certain embodiments, cooling product down from high temperature (e.g., 20 degrees Celsius or more above room temperature) is first accomplished by using air circulator 232 to flush an air space around the product with room temperature air, thereby saving cost of the cryogenic liquid, compressed gas and/or operation of the mechanical refrigerator unit. After a predetermined period of time or upon sensing a predetermined drop in temperature, the cryogenic liquid, compressed gas and/or mechanical refrigeration cooling may then be implemented to complete cooling of the product to a desired final temperature.

[0046] Air drawn into intake plenum 240 may be heated or cooled as needed to provide supply air at a desired temperature to test chambers 108 of system 100. As can be appreciated by one of skill in the art, the operation of certain types of thermal control elements 306 can cause increases or decreases in the volume of the chamber air in air circulator 232, which may be but is not necessarily a closed loop system. For example, cryogenic liquids and/or compressed gases utilized for cooling may be introduced into air circulator 232 and then expand to many times their original volume. Therefore, in certain embodiments, air circulator 232 can include a mechanism 340 for admitting or releasing air to maintain a constant or nearly constant air pressure with cabinet 104. Mechanism 340 may be, for example, an outlet pipe provided with a one way check valve, or a mechanism that includes a flapper that is pushed open by air pressure if internal pressure in system 100 exceeds air pressure external to system 100, but seals system 100 if the internal pressure is less than or about equal to the external pressure.

[0047] Air drawn through intake plenum 240 by fan 304 is passed through a fan outlet 316 to an air distribution or outlet plenum 320. As shown in FIG. 3, outlet plenum 320 has a depth d that generally decreases with distance from fan outlet 316. In addition, an air outlet 324 is provided for each test chamber 108. The decrease in the depth d of outlet plenum 320 provides an airflow staggered plenum that assists in the provision of equal amounts of temperature controlled air to test chambers 108. In addition, outlet plenum 320 can include other features to assist in equalizing the amount of air provided to each test chamber 108. For example, one or more diverters 328 can be provided to control the flow of air in outlet plenum 320.

[0048] Air circulator 232 can include one or more flow control devices 330. For example, a flow control device 330 comprising one or more diverters 328 can be included. A diverter 328 can include a surface or volume that forms a constriction in outlet plenum 320. Moreover, a diverter 328 can be located downstream of an air outlet 324. A diverter 328 comprising a constriction creates an area of elevated pressure that promotes a flow of air through air outlet 324 immediately upstream of diverter 328. Accordingly, diverter 328 can be used to balance the flow of air to test chambers 108. In accordance with still other embodiments, a diverter 328 can comprise a constriction with a movable surface or surfaces 334, to allow the size of the constriction in outlet plenum 320 to be varied, to vary the flow of air through a nearby air outlet 324. Alternatively or in addition, air outlet 324 may comprise a flow control device 330 in the form of a valve or grille that can be adjusted to control the flow of air through air outlet 324.

[0049] In accordance with other embodiments, outlet plenum 320 can have a depth that remains constant along the length of outlet plenum 320. In accordance with such

embodiments, the flow of air from outlet plenum 320 into individual test chambers 108 can be controlled by diverters, dampers, valves, or other flow control devices 330 placed between the fan or fans 304 and one or more of test chambers 108. For example, a flow control device 330 associated with an outlet 324 that is closest to fan 304 may be relatively more restrictive than a flow control device 330 associated with an outlet 324 that is downstream from the first outlet. For instance, an area of an outlet 324 relatively nearer to fan 304 may have an area that is less than an area of an outlet 324 relatively farther from fan 304. By thus differentially configuring flow control devices 330, flow to individual chambers 108 can be equalized, even though outlets 324 supplying those test chambers 108 are at different locations relative to fan 304. In accordance with still other embodiments, flow control devices 330 can comprise variable flow control devices 330. Moreover, variable flow control devices 330 may be under active control. For example, an active flow control device 330 may comprise an active diverter 328, with a surface 334 that is movable relative to a nearby outlet 324. In particular, by moving the surface, the area of outlet plenum 320 can be increased or decreased. This in turn allows flow through one or more outlets 324 to be adjusted. As still other examples, a flow control device 330 can comprise a variable damper.

[0050] FIG. 4A is a front elevation view of portions of an air circulator 232 for a product testing system 100 in accordance with another exemplary embodiment. In this embodiment, an air intake 236 is provided for each column of test chambers 108, and an air outlet 324 is provided for each of test chambers 108. In addition, air circulator 232 includes first 320a and second 320b outlet plenums. More particularly, first outlet plenum 320a is associated with a first column of test chambers 108, while second outlet plenum 320b is associated with a second column of test chambers 108. Product testing system 100 can include two fans 304a and 304b and each fan 304 can supply air to one of outlet plenums 320a and 320b. Accordingly, each outlet plenum 320a and 320b may be associated with a fan 304. The two fans 304 can draw air from a common intake plenum 240. Alternatively, intake plenum 240 can be divided into first 240a and second 240b intake plenums. Where separate intake plenums 240a and 240b are provided, they can each house separate thermal control elements 306a and 306b, including separate heating devices 308a and 308b and/or separate cooling devices 312a and 312b.

Alternatively, a common intake plenum 240 can house separate thermal control elements 306a and 306b, each of which entirely or primarily services an associated outlet plenum 320a and 320b. Moreover, the separate thermal control elements 306a and 306b can be separately controlled to provide different amounts of heating or cooling to the different columns of test chambers 108. For example, the illustrated embodiment may incorporate two tangential fans 304, with one fan 304a supplying air to a first column of test chambers 108 via first outlet plenum 320a, and a second fan 304b supplying air to a second column of test chambers 108 via the second outlet plenum 320b. Moreover, each fan 304a and 304b can be under separate control, to provide different amounts of air to the different outlet plenums 320a and 320b. In addition, each outlet plenum 320a and 320b includes one or more flow control devices 330. For example, the area of outlets 324 can vary with distance from intake plenum 240. Moreover, one or more of flow control devices 330 can comprise variable devices. For example, diverters 328 and/or outlets 324 can be operated to selectively vary the flow of air past or through flow control devices 330. Where variable flow control devices 330 are provided, they may be under active control. Moreover, a flow control device 330 associated with first outlet plenum 320a can be controlled separately from a flow control device 330 associated with second outlet plenum 320b. The width and/or depth of outlet plenums 320 can decrease with increasing distance from fan 304 supplying climate controlled air to outlet plenum 320. Alternatively, for example where diverters 328 or other flow control devices 330 are included, the depth and width of outlet plenums 320 can remain constant.

[0051] FIG. 4B is a front elevation view of portions of an air circulator 232 for a product testing system 100 in accordance with an exemplary embodiment. In this embodiment, an air intake 236 is provided for each column of test chambers 108. In addition, an air outlet 324 is provided for each of the test chambers 108. Accordingly, air circulator 232 in this embodiment includes air intakes 236 and air outlets 324 that are generally disposed in two parallel columns. In this example, a width W of outlet plenum 320 is constant. In accordance with other embodiments, width W may decrease as the distance from fan 304 increases. Accordingly, whether width W and/or depth d of the outlet plenum decreases, the volume of the outlet plenum can decrease with increasing distance from fan 304. Although air intakes 236 and air outlets 324 may be arranged in parallel columns, fan 304, intake plenum 240, and thermal control elements 306 within intake plenum 240 can be common to air circulator 232. Accordingly, these common components of air circulator 232 can supply thermally controlled air to test chambers 108 of system 100.

[0052] FIG. 4C is a schematic front elevation view of vibration table assemblies 208 in a product testing system 100, in accordance with still another embodiment. In this

embodiment, each vibration table assembly 208 is configured to utilize slides 207 for loading and unloading product tested within system 100. Slides 207, corresponding to each vibration table assembly 208, are arranged such that assembly 208 is at least slidable outwards within system 100. Slides 207 may be slides, but the term "slides" herein also encompasses devices including linear bearings, rollers, wheels and similar devices to facilitate lateral movement of a vibration table assembly into or out of system 100. A pair of slides 207 are shown for each assembly 208 in FIG. 4C, but certain embodiments may utilize only one slide 207; furthermore, single slides 207 may advantageously be mounted in other configurations such as from a rear surface of system 100. Slides 207 may also be configured so that vibration table assemblies 208 are completely removable from system 100. The use of slides 207 facilitates access to vibration tables 212 (e.g., as shown in FIG. 2) for convenient and quick loading and unloading of test chambers 108. In certain embodiments, slides 207 may also be configured to tilt each vibration table assembly 208 downwards as it fully withdraws from system 100, to further facilitate access to vibration tables 212. Also, in certain embodiments, test system 100 may include mounting hardware that, when vibration table assemblies 208 are fully within test system 100, mounts each vibration table assembly 208 rigidly to test system 100, disengaging from slides 207 so that moving parts or less robust parts of slides 207 do not become fatigued or introduce unintended vibrations during vibration testing. In these embodiments slides 207 may remain coupled with one or more of vibration assemblies 208, side walls 228 and center walls 230, or slides 207 may be removed, once the vibration tables 212 are mounted within system 100.

[0053] As can be appreciated by one of skill in the art after consideration of the present disclosure, the arrangement of air circulator 232 can be varied, in order to accommodate different test chamber 108 configurations. The arrangement of vibration table assemblies 208 and their corresponding intakes 236 and air outlets 324 can therefore be varied accordingly. For example, test chambers 108 can be organized in columns (e.g., each column consisting of at least two test chambers 108, one disposed atop the other) such that air circulator 232 includes at least one intake 236 for each column of test chambers 108, and at least one air outlet 324 for each test chamber 108. Alternatively, test chambers 108 can be organized in rows or subrows (e.g., each row consisting of at least two test chambers 108, each disposed adjacent to the other).

Furthermore, test chambers 108 need not be oriented with a vibration table 212 thereof in a horizontal orientation; vertical and diagonal vibration table orientation is also contemplated.

[0054] FIG. 4D illustrates some of the above-discussed embodiments. Comparing FIG. 4D to FIG. 4C, two chambers 108 including their associated vibration table assemblies 208 have been removed and replaced with two chambers 108' including their associated vibration table assemblies 208' disposed adjacent to one another, thus creating a row of chambers. Also, FIG. 4D shows vibration tables 212 associated with each vibration table assembly 208, 208'. The vibration tables associated with vibration table assemblies 208' have their vibration tables 212 oriented vertically instead of horizontally. Correspondingly, actuators within vibration table assemblies 208' impact their associated vibration tables from the side rather than from the underside. The vertical arrangement of vibration table assemblies 208' may facilitate populating a cabinet of system 100 with more chambers than would have otherwise been possible.

[0055] FIG. 4E is a schematic front elevation view of a product testing system 100 having a removable column 209 of chambers 108, in accordance with an embodiment. In FIG. 4E, removable column 209 includes four chambers 108, each associated with a vibration table assembly 208, as shown; however a removable column 209 may include any number of chambers. Slides 207 facilitate positioning and/or removal of removable column 209 within system 100, and may be removable after removable column 209 is in place within system 100, as discussed above.

[0056] FIG. 4F is a schematic front elevation view of the product testing system of FIG. 4E, with the removable column 209 removed and replaced with a product rack 213, in accordance with an embodiment. Slides 207 facilitate positioning and/or removal of product rack 213 within system 100, and may be removable after product rack 213 is in place within system 100, as discussed above. Product rack 213 can be utilized for product that is to be tested or screened by applying a thermal stress but without vibration. One skilled in the art will appreciate that testing product without vibration in a system 100 (e.g., on product rack 213) while identical product is tested with vibration in the same thermal environment (e.g., using chambers 108 within the same system 100) facilitates a clear comparison of reliability effects due to the thermal stress and the reliability effects due to the vibration. In embodiments, product rack 213 may take on a shape and/or size suitable for utilization within system 100 in place of any number or

combination of chambers 108. Furthermore, product rack 213 makes it possible to fill much of the available volume within a test system 100 with product, by eliminating the volume occupied by actuators, their support members and plumbing, and associated shrouds and other air enclosures, within system 100. The option of switching out thermal-plus- vibration test space within system 100 for thermal-only test space greatly enhances the flexibility and test capacity of system 100 in a high volume test environment, as may be required to support HAS A programs for high volume manufacturing of multiple product lines.

[0057] FIGs. 5A-5G illustrate different views of a vibration table assembly 208 that may be included in a product testing system 100 in accordance with certain embodiments. FIGs. 5A-5G show a vibration table 212 that includes an airtight plate 211 having a first side or mounting surface 214 that may include a plurality of fixture or fastener points 216. FIGs. 5F and 5G show a frame 21 Γ configured to couple with an airtight fixture tray 218 upon which product may be mounted. [0058] A plurality of hammers or actuators 520 are interconnected to a second side 504 of vibration table 212. Actuators 520 can be any type of actuators. For example, pneumatically operated actuators, electric motor actuators, hydraulic actuators, and/or any other type of device capable of accelerating or imparting force and/or other mechanical energy to a vibration table 212, can be used. In accordance with certain embodiments, actuators 520 are configured to provide movement of vibration table 212 in both translation and rotation with respect to the x, y and z axes. Accordingly, vibration table assembly 208 can provide table motion having six degrees of freedom. As shown in FIGs. 5D and 5E, a vibration table support 524 can provide perches or supports 528 for springs 508 adjacent or facing second side 504 of vibration table 212. As can be appreciated by one of skill in the art after consideration of the present disclosure, vibration table support 524 is fixed to cabinet 104.

[0059] Similar to the discussion above in connection with FIG. 2, although vibration tables 212 are shown as rectangular in FIGs. 5A-5F, it is contemplated that vibration tables 212, plates 211 and/or frames 211 ' may be curved, shaped or weighted in order to vary frequency response of the complete vibration table 212 when loaded with product and actuated.

[0060] In the embodiments of FIGs. 5A-5E, plate 211 is airtight, separating air around product mounted with mounting surface 214 from air beneath plate 211 , facilitating temperature control by isolating exhaust from actuators away from the product, as discussed below. Vibration table 212 is supported on a second side 504, opposite mounting surface 214, by one or more supports or table mount springs 508 that are mounted in-board of the edges of vibration table 212. Springs 508 can be any combination of compression, extension or leaf style. For example, the springs may be centered on points 512 that form corners of a rectangle that is itself centered in a rectangle 514 (see FIG. 5B) defined by mounting surface 214, and that defines an area that is equal to no more than 50% of an area of mounting surface 214. By providing an in-board mounting location for springs 508, vibration table 212 can better support a device under test as compared to a vibration table in which the springs are mounted at or close to the outer periphery of the table. For example, placing mounting springs 508 closer to a center of vibration table 212 allows for a less structurally substantial table, which can open up degrees of freedom in mechanical design of, and/or improve performance aspects of, vibration table 212. Specifically, a less structurally substantial table allows vibration table 212 to achieve a more broad frequency spectrum response, and especially improves the power of frequencies under 1000Hz.

[0061] In-board mounting of springs 508 also facilitates embodiments in which vibration table 212 includes a frame 211 ' instead of plate 211. FIG. 5F shows a frame 211 ' configured to couple with an airtight fixture tray 218 upon which product may be mounted. FIG. 5F includes shading of frame 211 ' to clarify large apertures therethrough, and shows airtight fixture tray 218 as a dashed outline only so that features of frame 21 Γ are visible therethrough. FIG. 5F also shows attachment points 530 for actuators and springs that support frame 21 1 ', at positions similar to those shown in FIG. 5B, in dashed lines. A peripheral edge of frame 21 1 ' couples with a shroud 224 (not shown in FIG. 5F, see FIG. 3 and FIG. 5G), but frame 211 ' is not airtight due to the apertures therethrough. When a peripheral edge of fixture tray 218 couples with frame 21 Γ (for example, by securing fixture tray 218 to frame 21 P at fixture or fastener points 216), fixture tray 218 and frame 21 P complete a seal 217 such that the shroud, frame 21 P and fixture tray 218 form a contiguously airtight surface. Although seal 217 is shown inboard of fastener points 216, it is contemplated that seal 217 could also form outboard of fastener points 216, and is not limited to the rectangular form shown, but could be of any shape where frame 21 P and fixture tray 218 meet. Seal 217 may simply form by contact of planar surfaces of frame 21 P with fixture tray 218 , or features such as gaskets may be provided to facilitate an airtight seal 217. Dashed line 5G-5G indicates a plane through the view of FIG. 5F that is shown in FIG. 5G.

[0062] FIG. 5G schematically illustrates along line 5G-5G of FIG. 5F, how fixture tray 218 completes seal 217 with frame 211,' and illustrates fixturing that can be utilized to mount product 10 for testing within system 100. FIG. 5G shows four sections of frame 211 ' as seen along line 5G-5G in FIG. 5F. Outermost sections of 21 P seal to edges of shroud portions 224 and 224' as shown in FIG. 5G. Therefore by sealing to outermost sections of frame 21 P at seal 217, fixture tray 218 completes a contiguously airtight seal from shroud portion 224 to shroud portion 224' . The contiguous seal isolates air below tray 218 from air above tray 218 so that air temperature around product 10, 10' can be controlled without interference from exhaust air or other gas emitted by actuators (e.g., actuators 520 discussed above). The use of fixture tray 218 with frame 211 ' can be considered to divide vibration table assembly 208 into two layers. An upper layer includes fixture tray 218, fixtures 540 (discussed below) and product coupled thereto. A lower layer includes frame 21 P coupled with shroud portions 224, actuators 520 and their associated plumbing or wiring, and mounted with springs 508 and their associated vibration table supports 524 and perches or supports 528. The two layer approach to isolating air above fixture tray 218 from air beneath it and around the actuators provides freedom and flexibility in the design of fixtures for quick loading and unloading in a production environment. The two layer approach also provides design freedom that can be used to finely tune the vibrational characteristics of the mechanical system formed by frame 211,' fixture tray 218, fixtures 540 and the product loaded thereon. That is, when a vibration table includes a plate 211, the size and rigidity of plate 211 itself can limit the vibrational modes achievable when fixturing and product is attached, whereas frame 211 ' may allow a user of system 100 to create product tray 218 and fixturing 540 such that the entire mechanical system supports vibrational modes not otherwise achievable.

[0063] FIG. 5G also schematically shows fixtures 540, 540', 540", 540' ' ' (collectively referred to as fixtures 540) that may be utilized to secure product 10, 10', 10" (collectively, product 10) to fixture tray 218. In other embodiments, one skilled in the art will appreciate that fixtures 540 may secure product 10 directly to plate 211 when a fixture tray 218 is not utilized (e.g., a plate 211 as shown in FIGs. 5A - 5E). Fixtures 540 may include elements such as manual, magnetic, pneumatic or vacuum clamps, bars, bolts, hinges, clasps, magnets,

electromagnets, electric motor actuators, springs, spring loaded devices, blocks configured to match a size and shape of product 10, and/or combinations of such elements. For example, fixtures 540 as shown in FIG. 5G are clamps that hold product 10 onto fixture tray 218; fixtures 540" are blocks configured to match a size and shape of product 10', and fixture 540' may be formed of a bar that is bolted to fixture tray 218 on either side of product 10'. In another example, fixture 540'" is a two piece fixture, hinged at 542 and clasped about product 10" at 543, and secured against plate 211 by vacuum applied from an underside of plate 211 by vacuum line 547 through a fitting 545. Applicants' definition of "airtight plate 211" includes the possibility of vacuum apertures extending through such plate 211 as long as such apertures are either connected to vacuum lines, such as vacuum line 547 shown, or (b) capped so as to maintain plate 211 as airtight from side to side. It is appreciated that any or all of vacuum, pneumatic, electromagnet, and/or electric motor actuated devices may be utilized in, or in connection with, fixtures 540 to facilitate automation of loading product 10 onto fixture trays 218 and/or directly onto vibration tables 212.

[0064] As mentioned above, each vibration table assembly 208 can be associated with a shroud 224 (shown in FIG. 3) such that when a vibration table 212 has an airtight plate 211 (e.g., as shown in FIGs. 5A-5E), or when an airtight fixture tray 218 completes a seal across open areas of a frame 211 ' (as shown in FIGs. 5F and 5G), vibration table assembly 208 forms an enclosed volume that contains springs 504 supporting vibration table 212, and actuators 520 that impart vibration to vibration table 212. Accordingly, the chamber air supplied by air circulator 232 is isolate from air surrounding actuators 520 and springs 508 of the vibration table.

Therefore, where actuators 520 comprise pneumatic hammers, exhaust air from actuators 520 does not mix with and disrupt the controlled temperature of the chamber air. As shown in FIG. 3, shroud 224 can include a front panel or portion 226. For a test chamber 108 that is positioned above another test chamber 108, shroud 224 can also include a bottom panel or portion 332 (see FIG. 3). Moreover, the bottom panel or portion 332 can be a separate component, or can comprise a surface of vibration table support 524. [0065] FIG. 6A is a block diagram depicting components of a product testing system 100, in accordance with an embodiment. As shown in FIG. 6A, product testing 100 includes an air circulator 232, a vibration table actuation subsystem 604, and a control subsystem 608.

Control subsystem 608 receives input 612 that is supplied to a controller 616 to control aspects of the operation of product testing system 100. Controller 616 may act as, or include, an optional vibration controller 650, an optional temperature controller 660, or both. (For clarity of illustration, labels of vibration controller 650 and temperature controller 660 are shortened to "Vibe" and "Temp" respectively in FIGs. 6A and 6B.)

[0066] In embodiments, controller 616 includes a vibration controller 650 for controlling vibration applied to a product under test through vibration tables 212. For example, vibration controller 650 may control vibration of all tables 212 of system 100 in parallel, or may control subsets, zones, or individual ones of vibration tables 212, as discussed further below.

[0067] Input 612 can include input entered through an input device by a user, and can also include programmed control parameters. Controller 616 may comprise a general purpose programmable processor, a controller with integrated memory, or other processor or computer implemented device for executing instructions. Instructions that are executed by controller 616 may be in the form of user input, programmed instructions stored in memory or data storage as software, and/or encoded firmware. More particularly, controller 616 may execute a control algorithm that implements or comprises a proportional-integral-derivative (PID) control system. Moreover, a controller 616 can include multiple processors, memory devices, and/or logic devices. As generally described herein, control subsystem 608 can provide control signals to air circulator 232 and vibration table system 604. In addition, control subsystem 608 can receive signals from sensors associated with air circulator 232 and/or vibration table actuation subsystem 604. Control subsystem 608 can also interface with external computers through a wired or wireless connection 670; connection 670 may for example be a network connection (e.g., the Internet) such that system 100, control subsystem 608, controller 616, chambers 108 and components thereof are network controllable.

[0068] Control signals provided by control subsystem 608 to air circulator 232 include signals provided to thermal control elements 306 located in the intake plenum 240. In particular, control signals provided by control subsystem 608 can direct thermal control elements 306 to heat or cool the air in intake plenum 240. Control subsystem 608 can also include control signals to control operation of fan 304. In addition, control subsystem 608 can provide control signals to active flow control devices 330, including but not limited to variable outlets 324, variable diverters 328, or variable air dampers 606. As depicted in FIG. 6A, air drawn through air intake 236 of air circulator 232 is received in intake plenum 240, where the air can be heated or cooled at the direction of control subsystem 608 by thermal control elements 306. Moreover, the air is drawn in through air intake 236 and intake plenum 240, across thermal control elements 306, by fan 304. The heated or cooled air is then passed by fan 304 to outlet plenum 320. From outlet plenum 320, the air is passed through air outlets 324 to individual test chambers 108. In the illustrated example, outlet plenum 320 supplies air to a first outlet 324a associated with a first test chamber 108a, a second outlet 324b associated with a second test chamber 108b, and an nth outlet 324n associated with an nth test chamber 108n. Accordingly, heated or cooled air is provided to a plurality of test chambers 108. Moreover, air circulator 232 can be configured such that heated or cooled air is supplied to any number of test chambers 108. Air provided to test chambers 108 is drawn back into intake plenum 240 through air intake or intakes 236.

Accordingly, air circulator 232 may recirculate thermally controlled test chamber air.

Alternatively or in addition, air circulator 232 can admit air from the ambient environment, or release air to the ambient environment, to control pressure levels within test chambers 108.

[0069] Air circulator 232 may make use of feedback in connection with control signals provided by control subsystems 608; this feedback may be implemented through controller 616 and/or optional temperature controller 660 therein. In particular, one or more of test chambers 108 may include a temperature sensor 620 - for example, a thermocouple - that can send a temperature signal to controller 616. Controller 616 (or optional temperature controller 660 therein) can use the information regarding the temperature of test chamber 108 provided by temperature sensor 620 to control thermal control elements 306, fan 304 and/or active flow control devices 330 such that air of a desired temperature is provided to test chambers 108. In the figure, a temperature sensor 620a, 620b, and 620n is associated with each of the first 108a, second 108b and nth 108n test chambers. Accordingly, controller 616 can use a temperature signal provided by any one of temperature sensors 620 to control operation of air circulator 232. Alternatively, an average temperature sensed by temperature sensor 620 can be used by controller 616, which can operate in response to a signal provided by any one of temperature sensors 620. Alternatively, a temperature sensor 620 need only be provided in one of test chambers 108, and the signal from that one temperature sensor 620 can be used to control air circulator 232.

Utilizing a single temperature sensor to provide feedback for all chambers in a system is useful when characterization of the chambers shows that they are fairly similar, in thermal aspects, to one another. This can be considered a "master/slave" control arrangement in which the measured chamber is the master and the other chambers are slaves. In accordance with still other embodiments, a temperature sensor 620 can be provided in another portion of air circulator 232, such as intake plenum 240 or in an outlet plenum 320. In accordance with still other

embodiments, for example where variable air outlets 324 and/or diverters 328 are included as part of air circulator 232, thermocouples may be placed within multiple chambers 108 or multiple locations within each chamber 108, so that controller 616 can operate to control the variable air outlets 324 and/or diverters 328. Moreover, variable air outlets 324 and/or diverters 328 can be controlled independently by controller 616, to provide individual control of the air temperature within different test chambers 108. Additional sensors can also be included to provide signals used by controller 616 in connection with control of air circulator 232. For example, one or more pressure sensors can be disposed within air circulator 232, to provide a signal to controller 616.

[0070] Controller 616 and/or optional vibration controller 650 can also be operated to control operation of vibration tables 208. More particularly, in the example illustrated in FIG. 6A, vibration table actuation subsystem 604 comprises a pneumatically operated system.

Accordingly, a source of supply air 624 provides operational air to a set of valves 628. For example, valves 628 may be provided for each set of actuators 520 included in vibration table assemblies 208 having a particular orientation, or for each set of actuators 520 in a given column of chambers 108, or for actuators in other predefined groups or zones of chambers. In the extreme, valves 628 may be provided for actuators 520 of each vibration table 208. Manifolds 632 then distribute the air supplied by valves 628 to those actuators 520. As can be appreciated by one of skill in the art, operation of actuators 520 imparts accelerations on tables 212. Exhaust air from actuators 520 can be collected in an exhaust plenum 636. The air from exhaust plenum 636 may be passed to the ambient environment. In accordance with still other embodiments, individual exhaust lines may be used to vent exhaust air directly from actuators 520 to the ambient environment.

[0071] One or more of vibration tables 212 may have one or more accelerometers 640 mounted thereto. In an embodiment, accelerometer 640 is a triaxial accelerometer that provides three dimensional vibration 'feedback for its vibration table. In other embodiments, accelerometer 640 is a linear accelerometer that provides feedback in one axis; in such embodiments, each vibration table 212 may utilize two or three accelerometers 640 to provide two or three axis feedback. (For clarity of illustration, certain instances of the temperature signals provided by temperature sensors 620 and accelerometers 640 are not shown in FIG. 6A.)

[0072] Accordingly, as shown in FIG. 6A, each vibration table 212 may be associated with an accelerometer (or plurality of linear accelerometers) 640a, 640b and 640n respectively. Signals from each accelerometer 640 can then be provided to controller 616, and a selected one of the signals, or an average of the signals, can be used by controller 616. In certain embodiments, only one of tables 212 needs to be associated with an accelerometer 640.

[0073] One skilled in the art appreciates from FIG. 6A and the above discussion thereof, that control subsystem 608, vibration table actuation subsystem 604 and air circulator 232 are interconnected but separable systems. Because they are separable, one control subsystem 608 may control several vibration table actuation subsystems 604 and/or air circulators 232; such subsystems 604 and air circulators 232 may be housed in the same cabinet 104 or in multiple cabinets 104, as now discussed.

[0074] FIG. 6B schematically shows an exemplary embodiment of a product test system 100 including one control subsystem 608 that controls table actuation subsystems 604 and air circulators 232 in multiple cabinets 104. Control subsystem 608 includes input 612 and controller 616, including vibration controller 650 and temperature controller 660, as in FIG. 6A. Control subsystem 608 controls vibration and/or temperature of chambers in cabinets 104(1), 104(2) and 104(3), as shown. Each cabinet 104 houses one or more vibration subsystems and/or one or more air circulators 232. Cabinet 104(1) houses one air circulator 232 and one actuation subsystem 604. Although not drawn to scale, in cabinet 104(1), air circulator 232 and actuation subsystem 604 are shown as relatively large, as would be appropriate for a HASA program for a high volume/low mix production line (that is, where the HASA program audits many of the same type of parts at a time). Cabinet 104(2) houses two air circulators 232, one of which controls air temperature associated with two actuation subsystems 604, the other of which is not associated with any actuation subsystems 604 (e.g., one or more chambers that are temperature controlled but do not use vibration). Cabinet 104(2) may be appropriate for a HASA program for a high volume/high mix product line (e.g., to audit many different products). Cabinet 104(3) houses one air circulator 232 and one actuation subsystem 604. Although not drawn to scale, in cabinet 104(3), air circulator 232 and actuation subsystem 604 are shown as relatively small, as would be appropriate for a HALT program for a low volume/low mix operation, such as a product development operation (that is, where HALT is utilized for initial reliability testing of new products). Each air circulator 232 and actuation subsystem 604 receives control signals from controller 616 that are collectively shown as control signals 680 (e.g., the signals that control thermal control elements 306, intake plenum 240, fan 304, supply air 624 and valves 628 as shown in FIG. 6A). Each air circulator 232 and actuation subsystem 604 also sends signals to controller 616 that are collectively shown as sensor signals 690 (e.g., the signals from

temperature sensors 620 and accelerometers 640, as shown in FIG. 6A).

[0075] A method for providing a product testing system is illustrated in FIG. 7, in accordance with an embodiment. The method may be performed by or in association with the execution of a control algorithm by controller 616. According to the method, a plurality of test chambers 108 are disposed within a cabinet 104 (step 704). Each test chamber is associated with a vibration table assembly 208. In addition, the cabinet includes an air circulator 232 with at least one intake 236 and at least one air outlet 324 in communication with each test chamber 108. Cabinet door or doors 204 are opened to access the plurality of test chambers 108 (step 708). At least one device or product under test is then placed on and interconnected to each vibration table 208 (step 712). After the devices to be tested have each been interconnected to a vibration table 208, cabinet door or doors 204 are closed (step 716).

[0076] Operation of the air circulator can then be initiated (step 720). In particular, fan or fans 304 can be turned on, to draw air in through air intake or intakes 236, through intake plenum 240 and across or past thermal control elements 306. The now heated or cooled air is then forced down outlet plenum 320 and out air outlets 324 into test chambers 108. Forcing the air out air outlets 324 can include diverting the air in outlet plenum 320. More particularly, a diverter may be disposed within outlet plenum 320, downstream of an air outlet 324 that forms a constriction to promote a flow of air through air outlet 324. This use of diverters 328 allows pressures at air outlets 324 to be equalized, to provide identical or near identical air flow and thermal conditions or stresses to devices under test in each of test chambers 108. Alternatively or in addition, air outlets 324 and/or dampers 606 or other flow control devices 330 that can be actively controlled can be provided.

[0077] Operation of vibration tables 208 can also be initiated after access doors 204 are closed (step 724). In certain embodiments, the vibration tables 208 may accelerate an attached device, and may do so with six degrees of freedom. In accordance with these and other embodiments, all of vibration tables 208 may operate to impart the same series of accelerations to attached devices, such that identical stresses are imparted to the devices. Control of the vibration tables may be in connection with information provided by an accelerometer. The accelerometer may be attached to one of vibration tables 208. Alternatively, more than one or even all of vibration tables 208 may include an accelerometer.

[0078] At step 728, a determination can be made as to whether the run time for the test or burn in procedure being performed has been completed. If the run time has been completed, the process may end. Otherwise, the process will continue until the prescribed run time has been reached (step 732).

[0079] FIG. 8 is a block diagram depicting some of the components of a product testing system 100 in accordance with other embodiments. More particularly, FIG. 8 illustrates air circulator 232 of an exemplary embodiment of a multiple test chamber 108 system 100 with first 232a and second 232b air circulators. The first air circulator 232a may be associated with a first column of test chambers 108, while second air circulator 232b may be associated with a second column of test chambers 108. In this embodiment, a common control subsystem 608 is shown. Control subsystem 608 receives input 612 that is supplied to controller 616.

Accordingly, in certain respects, control subsystem 608 is similar to the control subsystem 608 in connection with embodiments that include a single air circulator 232. In order to separately control multiple air circulators 232a and 232b in the embodiment illustrated in connection with FIG. 8, controller 616 may implement parallel control algorithms. These parallel algorithms may be implemented by separate processors, or by a single processor implementing multiple virtual instances. In accordance with still other embodiments, controller 616 can implement a single processor algorithm that provides separate control to various components of air circulators 232a and 232b. For instance, the algorithm executed by controller 616 can implement a PID control system or algorithm that operates in response to temperature information provided by temperature sensors 620a to operate thermal control elements 306a and 306b such that differences in temperature between a first zone comprising the first column of one or more test chambers 108 and a second zone comprising the second column of one or more test chambers are reduced or eliminated. As a further example, the PID control algorithm can use temperature information from a temperature sensor 620 in the first column of test chambers 108 as a primary input, and can then add heat in pulses through the selective operation of a heating device 308 associated with the column of test chambers 108 that a comparison between a temperature sensor 620 associated with the first column and a temperature sensor 620 associated with the second column indicates has a lower temperature. Accordingly, a differential algorithm included in the main algorithm can operate thermal control elements 306 associated with one of the columns of test chambers 108 and associated air circulator 232a or 232b differentially.

[0080] The provision of first 232a and second 232b air circulators can provide enhanced thermal control with respect to various test chambers 108 included in system 100. For example, thermal control elements 306a and 306b and fans 304a and 304b can be controlled separately for each air circulator 232a and 232b. For example, where a first air circulator 232a is associated with a first column of test chambers 108, and a second air circulator 232b is associated with a second column of test chambers 108, temperature control of system 100 can be by zone, with a first zone comprising the first column of test chambers 108 associated with first air circulator 232a and the second zone associated with the second column of test chambers 108 associated with second air circulator 232b. In accordance with still other embodiments, air outlets 324 can comprise actively controlled flow control devices 330. These air outlets 324 can be individually controlled by controller 616 to achieve and maintain a desired temperature within individual test chambers 108 in response to temperature sensors 620 associated with those test chambers 108. Accordingly, different heat loads and/or sinks introduced by different

arrangements of devices under test within test chambers 108 can be accommodated.

[0081] FIGs. 9 and 10 illustrate outlets 324 of a test chamber 108 comprising active flow control devices 330 with a grill or louver assembly 904. Grill assemblies 904 can include individual flow control elements or vanes 908 to direct the flow of air provided by outlet plenum 320 to the associated test chamber 108. In particular, the embodiment illustrated in FIG. 9 incorporates vertically aligned vanes 908, to divert the air flow in a horizontal direction. FIG. 10 illustrates an air outlet 324 comprising a grill assembly 904 with vanes 908 that are arranged horizontally to control the flow of air in a vertical direction within test chamber 108. Individual vanes 908 can be adjusted to provide an air flow that is adapted to the particular configuration, number and/or arrangement of devices under test, to provide a suitably uniform flow and/or temperature within the associated test chamber 108. This control can be manual or at the direction of controller 616. For example, vanes 908 can be associated with motors or other control actuators operated in response to control commands provided by controller 616.

[0082] In accordance with still other embodiments, a grill assembly 904 can include restrictor plates and/or vertically, horizontally, angled or curved arranged vanes 908. In addition to controlling the direction of flow, vanes 908 can be used to provide different air flow amounts to different areas of an associated test chamber 108, and to control the total amount of air flow through the test chamber.

[0083] FIG. 11 is a schematic diagram of product testing system 100 of FIGs. 1, 2, 3, 4 A through 4F, 6 A, 6B and 8, illustrating further detail for exemplary control of temperature within test chamber(s) 108. Controller 616 is shown with memory 1102, a processor 1112, and a profile clock 1114. Memory 1102 may represent one or both of volatile memory (e.g., random access memory) and non-volatile memory (e.g., read-only memory, flash memory, disk drives). Profile clock 1114 is for example a timer of controller 616 that periodically matures indicating a control cycle (e.g., a defined portion) of a temperature profile of system 100 is complete and a new control cycle is starting. The control cycle is for example a period of one second. Memory is shown storing a desired profile 1104, logged data 1106, an adjusted profile 1107, and software 1105 including a PID 1108, and a converging algorithm 1110. Although PID 1108 is shown as stored within memory 1102, PID 1108 may be implemented at least partially external to controller 616 (e.g., as hardware, field programmable gate arrays, or other electronic components) and controlled by controller 616, without departing from the scope hereof. Air circulator 232 includes a temperature throttle 1116, and optionally a fan throttle 1118 and a flow throttle 1120. Each of the throttles is a controller for a corresponding physical element in air circulator 232; that is, temperature throttle 1116 controls (one or more) thermal control elements 306, fan throttle 1118 controls fan 304, and flow throttle 1120 controls (one or more) variable flow devices 330. A throttle value implemented by each of throttles 1116, 1118 and 1120 adjusts the operation of the corresponding physical element accordingly. Also, although FIG. 11 describes thermal control elements 306 and illustrates only one fan 304 and variable flow device 330, each of these physical elements may be present in different numbers in air circulator 232 than are shown in FIG. 11. Processor 1112 executes software 1105 to provide functionality of controller 616 as described below.

[0084] One exemplary desired profile 1104 is illustratively shown in FIG. 19, which is a graph 1900 of temperature against time. In graph 1900, a solid line 1902 represents a desired temperature over time for test chamber 108, as defined by desired profile 1104, and a dashed line 1904 represents an actual temperature as measured in test chamber 108. Graph 1900 depicts desired temperature and actual temperature over a "run" that includes a series of temperature changes, ending at the same temperature at which the run began. Reliability tests often include subjecting product to many such "runs" in succession, with or without vibration. It can be seen in graph 1900 that the actual temperature does not match the desired temperature at areas denoted as 1906, where the temperature does not change as quickly as desired, over time, and at areas denoted as 1908, where the temperature overshoots the desired temperature change before returning to the desired temperature.

[0085] Converging algorithm 11 10 is for example an iterative process of using stored data within logged data 1106 that includes one or more of measured temperature values of test chamber 108, temperature throttle values, fan throttle values, and flow throttle values that were recorded during previous runs of system 100, as controlled for example by PID response to temperature error between measured chamber temperature and the desired profile. The stored data within logged data 1106, desired profile 1104, and adjusted profile 1107 are time based, and converging algorithm 11 10 generates adjusted profile 1107 to define one or more of temperature throttle values, fan throttle values, and flow throttle values as time based throttle settings for controlling one or more of thermal control elements 306, fan 304, and variable flow device 330, so that actual temperature within test chamber 108 follows desired profile 1104. In one embodiment, converging algorithm 1110 uses linear interpolation to generate desired profile 1104 based upon one or more of measured temperature values of test chamber 108, temperature throttle values, fan throttle values, and flow throttle values that were recorded during previous runs of system 100.

[0086] In operation, converging algorithm 1110 compares defined temperatures within desired profile 1104 against stored measured temperatures within logged data 1106, and the stored throttle settings are adjusted up or down based upon the difference therebetween. For example, if the measured temperature stored within logged data 1106 for a particular period is lower than the defined temperature within desired profile 1104, converging algorithm 1110 may define adjusted profile 1107 to have a temperature throttle value that is increased (for example, by 5%) over the stored temperature throttle value within logged data 1106. Similarly, converging algorithm 1110 may adjust temperature throttle down (for example, by 5%) when temperature overshoots the desired profile 1104. Converging algorithm 1110 may then execute during subsequent runs to further adjust throttle values where error is still occurring. After a defined number of runs (e.g., three runs), throttle settings within adjusted profile 1107 are used as fundamental control of one or more of thermal control elements 306, fan 304, and variable flow device 330, and one or more PID functions may be used as adjustments to the fundamental control, to correct any further deviation from the desired temperature. For example, PID 1108 may be used to adjust for changes in thermal mass of any test products placed within test chamber 108. In one embodiment, converging algorithm 1110 is invoked until measured temperature response is within defined criteria, whereupon no further adjustment of throttle values is required and controller 616 utilizes defined throttle values of adjusted profile 1107.

[0087] Outputs of controller 616 optionally control one or more of a temperature throttle 1116 of thermal control elements 306, a fan throttle 1118 of fan 304 and a flow throttle 1120 of variable flow device 330. One or more temperature sensors 620 within one or more test chambers 108 provide temperature feedback to controller 616 to allow controller 616 to control temperature and flow rate of air 1124 into test chamber 108.

[0088] Controller 616 may control temperature of multiple test chambers 108 using shared (between test chambers) thermal control elements 306 as shown in the embodiment of FIG. 6A, and/or may control multiple air circulators 232, where each air circulator 232 includes thermal control elements 306 and one or more test chambers 108.

[0089] FIGs. 12 -18 are flowcharts illustrating one exemplary method 1200 for controlling temperature within the test chamber of FIGs. 1, 2, 3, 4, 6, and 8, in accordance with an embodiment. Method 1200 is for example implemented within controller 616 of system 100 and is invoked each cycle of desired profile 1104.

[0090] In step 1202, method 1200 determines a profile temperature for the test chamber. In one example of step 1202, controller 616 determines a desired temperature for test chamber 108 based upon a current cycle of desired profile 1104. In step 1204, method 1200 reads the chamber temperature. In one example of step 1204, a temperature sensor 620 is placed in a specific test chamber 108, and controller 616 reads a temperature of the specific test chamber 108 from temperature sensor 620. In another example of step 1204, controller 616 reads a temperature from each of a plurality of temperature sensors 620 located within one or more test chambers 108, and averages the measured temperature values.

[0091] Step 1206 is a decision. If, in step 1206, method 1200 determines that more than a predetermined number of runs (e.g., three runs) of the temperature cycle have completed, method 1200 continues with step 1220; otherwise, method 1200 continues with step 1208. [0092] In step 1208, method 1200 invokes temperature throttle sub-method 1300 of FIG. 13.

[0093] Step 1210 is optional. If included, in step 1210, method 1200 invokes fan throttle sub-method 1400 of FIG. 14.

[0094] Step 1212 is optional. If included, in step 1212, method 1200 invokes flow throttle sub-method 1500 of FIG. 15.

[0095] Step 1216 is a decision. If, in step 1216, method 1200 determines that the current run is the first, method 1200 exits; otherwise, method 1200 continues with step 1218. In step 1218, method 1200 utilizes a converging algorithm to determine an adjusted profile that improves temperature control of the test chambers. In one example of step 1218, controller 616 executes converging algorithm 1110 to process logged data 1106 against desired profile 1104 to determine settings for one or more of temperature throttle 1116, fan throttle 1118, and flow throttle 1120 to form adjusted profile 1107.

[0096] In step 1220, method 1200 invokes adjusted temperature control sub-method 1600 of FIG. 16.

[0097] Step 1222 is optional. If included, in step 1222, method 1200 invokes adjusted fan control sub-method 1700 of FIG. 17.

[0098] Step 1224 is optional. If included, in step 1224, method 1200 invokes adjusted flow control sub-method 1800 of FIG. 18. Method 1200 then terminates.

[0099] Method 1200 repeats for each run of desired profile 1104 to control temperature within test chamber 108.

[0100] In step 1302, sub-method 1300 stores the measured chamber temperature of step 1204 within logged data. In one example of step 1302, controller 616 stores the temperature measured from temperature sensor 620 in step 1204 within logged data 1106 in association with the current cycle of desired profile 1104. In step 1304, sub-method 1300 uses the PID to calculate a temperature throttle based upon the determined profile temperature of step 1202 and a measured temperature. In one example of step 1304, controller 616 executes PID 1108 using processor 1112 based upon a current cycle of desired profile 1104 and a temperature measured by temperature sensor 620 in step 1204, to calculate a temperature throttle for thermal control elements 306.

[0101] In step 1306, sub-method 1300 stores the calculated temperature throttle in the logged data. In one example of step 1306, controller 616 stores the calculated temperature throttle value of step 1304 within logged data 1106 with respect to the current cycle of desired profile 1104. In step 1308, sub-method 1300 sets the temperature throttle of the thermal control elements. In one example of step 1308, controller 616 sets temperature throttle 1116 based upon the temperature throttle value calculated in step 1304, to control operation of thermal control elements 306.

[0102] Sub-method 1300 then returns control to method 1200.

[0103] In step 1402, sub-method 1400 uses a PID to calculate a fan throttle based upon the determined profile temperature of step 1202, the determined temperature throttle of sub- method 1300, and a measured temperature. In one example of step 1402, controller 616 executes PID 1 108 using processor 1 1 12 based upon a current cycle of desired profile 1 104, the determined temperature throttle value of sub-method 1300, and a temperature measured by temperature sensor 620 in step 1204, to calculate a fan throttle value for fan 304.

[0104] In step 1404, sub-method 1400 stores the calculated fan throttle value in the logged data. In one example of step 1404, controller 616 stores the calculated fan throttle value of step 1402 within logged data 1 106 with respect to the current cycle of desired profile 1104. In step 1406, sub-method 1400 sets the fan throttle of the fan. In one example of step 1406, controller 616 sets fan throttle 1 1 18 based upon the fan throttle value calculated in step 1402, to control operation of fan 304.

[0105] Sub-method 1400 then returns control to method 1200.

[0106] In step 1502, sub-method 1500 uses a PID to calculate a flow throttle based upon the determined profile temperature of step 1202, the determined temperature throttle of sub- method 1300, the determined fan throttle of sub-method 1400, and a measured temperature. In one example of step 1502, controller 616 executes PID 1108 using processor 1 112 based upon a current cycle of desired profile 1 104, the determined temperature throttle value of sub-method 1300, the determined fan throttle value of sub-method 1400, and a temperature measured by temperature sensor 620 in step 1204, to calculate a flow throttle value for variable flow device 330.

[0107] In step 1504, sub-method 1500 stores the calculated flow throttle value in the logged data. In one example of step 1504, controller 616 stores the calculated flow throttle value of step 1502 within logged data 1 106 with respect to the current cycle of desired profile 1 104. In step 1506, sub-method 1500 sets the flow throttle of the variable flow device. In one example of step 1506, controller 616 sets fan throttle 1 118 based upon the flow throttle value calculated in step 1502, to control operation of variable flow device 330.

[0108] Sub-method 1500 then returns control to method 1200.

[0109] If included, sub-method 1600 is invoked from step 1220 of method 1200.

[0110] In step 1602, sub-method 1600 determines a temperature throttle value from the adjusted profile. In one example of step 1602, controller 616 determines a temperature throttle value from adjusted profile 1 107. In step 1604, sub-method 1600 uses a PID to calculate a temperature throttle delta for the temperature throttle, based upon recorded temperature within the logged data and a temperature within the test chamber. In one example of step 1604, controller 616 executes PID 1 108 using processor 11 12 to calculate a temperature throttle delta value based upon recorded temperature of step 1302 of sub-method 1300, and a measured temperature of test chamber 108 using temperature sensor 620 of step 1204. In step 1606, sub- method 1600 outputs the temperature throttle of step 1602, adjusted by the temperature throttle delta value of step 1604, to the thermal control elements. In one example of step 1606, controller 616 adds the temperature throttle delta value of step 1604 to the temperature throttle determined in step 1602, and outputs the result to temperature throttle 1 1 16 to control thermal control elements 306.

[0111] Sub-method 1600 then returns control to method 1200.

[0112] If included, sub-method 1700 is invoked from step 1222 of method 1200.

[0113] In step 1702, sub-method 1700 determines a fan throttle value from the adjusted profile. In one example of step 1702, controller 616 determines a fan throttle value from adjusted profile 1 107. In step 1704, sub-method 1700 uses a PID to calculate a fan throttle delta for the fan throttle based upon recorded temperature within the logged data and temperature within the test chamber. In one example of step 1704, controller 616 executes PID 1 108 using processor 1 112 to calculate a fan throttle delta value based upon recorded temperature of step 1302 of sub-method 1300, and a measured temperature of test chamber 108 using temperature sensor 620 of step 1204. In step 1706, sub-method 1700 outputs the fan throttle of step 1702, adjusted by the fan throttle delta value of step 1704, to the fan. In one example of step 1706, controller 616 adds the fan throttle delta value of step 1704 to the fan throttle determined in step 1702, and outputs the result to fan throttle 1118 to control fan 304.

[0114] Sub-method 1700 then returns control to method 1200.

[0115] If included, sub-method 1800 is invoked from step 1224 of method 1200.

[0116] In step 1802, sub-method 1800 determines a flow throttle value from the adjusted profile. In one example of step 1802, controller 616 determines a flow throttle value from adjusted profile 1 107. In step 1804, sub-method 1800 uses a PID to calculate a flow throttle delta for the flow throttle based upon recorded temperature within the logged data and temperature within the test chamber. In one example of step 1804, controller 616 executes PID 1 108 using processor 1 1 12 to calculate a flow throttle delta value based upon recorded temperature of step 1302 of sub-method 1300, and a current measured temperature of test chamber 108 using temperature sensor 620. In step 1806, sub-method 1800 outputs the flow throttle of step 1802, adjusted by the flow throttle delta value of step 1804, to the variable flow device. In one example of step 1806, controller 616 adds the flow throttle delta value of step 1804 to the flow throttle determined in step 1802, and outputs the result to flow throttle 1120 to control variable flow device 330.

[0117] Sub-method 1800 then returns control to method 1200.

[0118] FIG. 20 is a graph 2000 of temperature against time with a solid line 1902 representing a desired temperature for the test chamber of FIGs. 1, 2, 3, 4, 6, 8 as shown in FIG. 19 and a dotted line 2004 representing an expected temperature of test chamber 108 as controlled using adjusted profile 1107 of FIG. 11, in accordance with an embodiment. As seen in graph 2000, temperature of test chamber 108 follows the desired temperature of the temperature profile indicated by line 1902 more closely, with minimal undershoot 2006 and reduced overshoot.

[0119] Although certain examples have depicted and described a test system 100 including a cabinet 104 housing six test chambers 108 disposed in two columns of three, embodiments herein are not limited to such a configuration. In general, embodiments herein have application to any test system 100 incorporating a plurality of test chambers 108. In addition, although a cabinet 104 with access doors 204 only is illustrated, some embodiments may have doors configured to allow access to test chambers 108 as deemed necessary or convenient for a particular use or application. In accordance with embodiments that make use of a common controller 616, controller 616 can operate by executing a single copy or instance of a control algorithm. Accordingly, multiple test chambers 108 can be provided with thermally controlled air, and vibration tables 212 in each of test chambers 108 can be operated in a like manner using a single controller 616 and control algorithm. In connection with such embodiments, a temperature sensor 620 associated with any one of test chambers 108 or any other portion of air circulator 232 to provide temperature information to controller 616. A single accelerometer 640 associated with any one of tables 212 can be used to provide controller 616 with acceleration information. In accordance with such embodiments, it is advantageous that test chambers 108, vibration table assemblies 208 and attached devices under test be configured identically. Although various examples provided herein discuss the use of pneumatic actuators 520, any type of actuator may be used.

Combinations of Features

[0120] Embodiments herein can be combined in any of the following ways, and others that will be apparent to one of skill in the art after reading and understanding the present disclosure.

A. A product testing system may include a plurality of vibration tables controllable to vibrate product mounted with the vibration tables; and an air circulator for controlling air temperature of air surrounding the product. B. The system denoted above as A may include a system controller for controlling the air temperature and vibration applied to the vibration tables.

C. The systems denoted above as A or B may include a system controller having a vibration controller for controlling the vibration.

D. The systems denoted above as A, B or C may include a vibration controller operable to separately control vibration of (a) each of the vibration tables or (b) one or more subsets of the plurality of vibration tables.

E. The systems denoted above as A through D may include a temperature controller for controlling the air circulator to adjust the air temperature.

F. The systems denoted above as A through E may include the air circulator having at least one thermal control element, ducting and at least one fan cooperating to adjust the air temperature. Such thermal element may be one of a heating element and a cooling element.

G. The systems denoted above as A through F may include an electric resistance heating element as a thermal control element.

H. The systems denoted above as A through G may include the air circulator configured to cool the product utilizing a cryogenic liquid. In these systems, the air circulator may be configured to cool the product from a temperature that is at least 20 degrees Celsius above room temperature by (a) flushing a chamber corresponding to the product with room temperature air, then (b) utilizing the cryogenic liquid.

I. The systems denoted above as A through H may include one or more of the vibration tables being removable from the system to facilitate mounting of product thereon.

J. The systems denoted above as A through I may include a cabinet housing the vibration tables, one or more of the vibration tables being slidable into and out of the cabinet, to facilitate mounting of product thereon. In these systems, the vibration tables may slide into and out of the cabinet on slides, linear bearings, rollers or wheels.

K. The systems denoted above as A through J may include mounting hardware for mounting each of the vibration tables rigidly within the system.

L. The systems denoted above as A through K may include a fixture operable to mount the product to the vibration tables. The fixture may include one or more elements selected from the group consisting of: manual clamps, magnetic clamps, pneumatic clamps, vacuum clamps, bolts, bars, hinges, clasps, magnets, electromagnets, electric motor actuators, springs, spring loaded devices, and holding blocks configured to match a shape and size of the product.

M. The systems denoted above as A through L may include a plurality of chambers, each chamber enclosing one of the vibration tables and having controllable actuators that generate vibration applied to the product. In these systems, (i) at least two of the chambers may have different size or shape; (ii) at least one of the vibration tables may be configured along a wall or ceiling of its chamber; (iii) the air circulator may include controllable air flow vanes operable to selectively adjust one or both of flow rate and direction of air flowing through at least one of the chambers; and (iv) at least one of the chambers may be disposed atop another chamber to form a column.

N. The systems denoted above as A through M may include the air circulator configured to control the air temperature separately for each of a plurality of chambers. In these systems, (i) at least two of the chambers may have different size or shape; (ii) the air circulator may include controllable air flow vanes operable to selectively adjust one or both of volume and direction of air flowing through at least one of the chambers; (iii) at least one of the chambers may be disposed atop another chamber to form a column.

O. The systems denoted above as A through N may include a cabinet for housing a plurality of chambers, and the cabinet may include at least one access door for chambers that form a column. In these systems, (i) the access door may form a plurality of access doors, wherein closing each of the access doors isolates one or more of the chambers from room air, and wherein opening at least one access door does not modify isolation of chambers corresponding to at least one other access door; (ii) one or more of the chambers may be vertically adjustable in height within the cabinet; (iii) the column may be removable from the cabinet, and the system may further include a product rack for placement within the cabinet where a removed column was, such that product may be placed on the product rack at controlled air temperature within the cabinet; (iv) the system may include, for each of the chambers, a screwless skirt for

environmentally separating vibration actuators from a respective vibration table, the actuators may include pneumatic actuators, and the skirt and respective chamber may form a labyrinth seal; (vi) the air circulator may include an air flow staggered plenum to provide uniform flow to each chamber in the column, the plenum being shaped at a back wall of the cabinet; and/or (vii) the system may include a controller for controlling air temperature and a vibration profile for each vibration table of a chamber, each of the chambers including (a) at least one thermocouple providing temperature measurement feedback to the controller and (b) at least one accelerometer providing acceleration feedback to the controller, to facilitate active feedback control of temperature and vibration profile, respectively.

P. The systems denoted above as A through O may include a cabinet for housing a plurality of chambers, the cabinet may include at least one access door for chambers that form a column, and the air circulator may include an air flow staggered plenum to provide uniform flow to each chamber in the column. In these systems, vibration of tables within the column may be controllable as a group, and/or the air flow staggered plenum may connect to each chamber in the column via an air outlet, wherein an area of an air outlet farther from a fan of the air circulator is smaller than an area of an air outlet nearer to the fan.

Q. The systems denoted above as A through P may include a cabinet for housing a plurality of chambers, the cabinet may include at least one access door for chambers that form a column, and the air circulator may include an air flow staggered plenum to provide uniform flow to each chamber in the column. In these systems, one or more of the chambers may include at least one thermocouple providing temperature measurement feedback to the controller, and at least one accelerometer providing acceleration feedback to the controller, to facilitate active feedback control of temperature and vibration profile, and (i) the at least one accelerometer may be, or include, a triaxial accelerometer operable to provide three dimensional vibration feedback for its vibration table; (ii) the at least one accelerometer may be a first linear accelerometer and a second linear accelerometer orthogonal to the first linear accelerometer, providing dual axis feedback for its vibration table.

R. The systems denoted above as A through Q may be configured such that temperature and vibration for each chamber are network controllable.

S. The systems denoted above as A through R may include vibration tables having a frame having vibration actuators coupled thereto, and a fixture tray for coupling the product thereto, the frame and the fixture tray configured to alternatively (a) couple together rigidly within the system and (b) decouple such that the fixture tray is removable from the system. In such systems, (i) the frame may include an airtight plate isolating the air surrounding the product from actuator exhaust; (ii) a frame that is not airtight, but wherein the fixture tray is airtight, such that mounting the fixture tray to the frame isolates the air surrounding the product from actuator exhaust, or (iii) each of the vibration tables may include two layers, a first one of the layers forming a frame connected to vibration actuators, the second one of the layers forming a fixture tray for mounting product thereon, and further comprising a cabinet and plurality of chambers, each chamber comprising the second layer such that (a) the chamber is environmentally separated within the cabinet when two layers of its respective vibration table rigidly couple together, and alternatively (b) when two layers of its respective vibration table are decoupled, the chamber is removable from the cabinet.

T. The systems denoted above as A through S may include at least one of the vibration tables being vertically and selectively moveable to facilitate placement of product mounted thereon.

U. The systems denoted above as A through T may include a cabinet and plurality of chambers, each chamber enclosing one of the vibration tables and having separately controllable actuators causing table vibration, the air circulator configured such that each of the chambers is separately controllable in air temperature, each chamber being adjustable in height within the cabinet. In such systems, two or more of the chambers may be networked together for common vibration and air temperature operation

V. The systems denoted above as A through U may include electric motor actuated fixturing operable to automate, at least in part, attachment of product to each of the tables.

W. The systems denoted above as A through V may have at least one vibration table including one or more vacuum, pneumatic, electromagnet, and/or electric motor actuated devices that are controllable to alternatively attach product to the vibration table and release product from the vibration table.

X. The systems denoted above as A through W may include a cabinet for housing the chambers, the cabinet comprising at least one access door for the column.

Y. The systems denoted above as A through X may test a product that includes electronics, with or without fixturing.

Z. The systems denoted above as A through X may include at least one of the vibration tables being curved, shaped or weighted to vary vibrational frequency response of the at least one vibration table, over an area of the table, when actuated.

AA. The systems denoted above as A through Z may include a plurality of tangential fans, each of the fans providing airflow to product in chambers that are arranged in a vertical column. In such systems, the tangential fans may be configured along a common drive axis driven by a motor and/or belts.

AB. The systems denoted above as A through AA may include a centrifugal blower.

AC. A vibration tray may include: a table top and fixturing for coupling product to the table top, wherein the table top may be selectively affixed to mating structure within a product testing system and actuated to function as a vibration table within the product testing system, and the table top may be selectively removed from the mating structure to facilitate coupling and decoupling of product to the table top.

AD. A product testing controller may include means for controlling vibration of a plurality of vibration tables in a common cabinet; and means for controlling air temperature surrounding product mounted on the vibration tables.

AE. The system denoted above as AD may include the means for controlling air temperature forming means for controlling an air circulator driving airflow within the cabinet.

AF. The systems denoted above as AD or AE may include the means for controlling vibration utilizing acceleration feedback from one or both of (a) at least one of the vibration tables, and (b) product mounted to at least one of the vibration tables, to control the vibration. AG. The systems denoted above as AD, AE or AF may include the means for controlling air temperature utilizing temperature feedback from one or both of (a) air temperature sensors and (b) product temperature sensors, to control the air temperature.

AH. An environmentally sealable vibration chamber may include a vibration table for mounting product thereto, and one or more vibration actuators responsive to drive signals for vibrating the vibration table. The chamber may be selectively affixed within a product testing system providing the drive signals and controlling air temperature within the chamber, and the chamber may be selectively removed from the system to facilitate coupling and decoupling of product to the vibration table.

AI. A test system may include a test cabinet; a plurality of test chambers disposed within the test cabinet; an air circulator including an air intake, a plurality of air outlets, wherein at least one air outlet is associated with each test chamber in the plurality of test chambers, an intake plenum, a fan, wherein the fan is supplied with air from the intake plenum, and an outlet plenum, wherein the fan supplies air to the outlet plenum; and a plurality of vibration tables, wherein each test chamber in the plurality of test chambers includes at least one vibration table.

AJ. The test system denoted above as AI may include a vibration table shroud, wherein at least one of the vibration tables is associated with a vibration table shroud; and/or a plurality of vibration table actuators, wherein each vibration table in the plurality of vibration tables is associated with a vibration table actuator, and wherein the vibration table shroud of the at least one of the vibration tables encloses the vibration table actuator for that vibration table, and defines a volume that is separate from the air circulator.

AK. The test system denoted above as AI or AJ may include at least one vibration table shroud associated with a vibration table that (i) is disposed above another vibration table, and (ii) includes a front panel and a bottom panel.

AL. The test systems denoted above as AI, AJ or AK may include all of the vibration tables being associated with a vibration table shroud, wherein at least one vibration table shroud associated with a vibration table at a bottom of a column of vibration tables includes a front panel, and wherein at least one vibration table shroud associated with a vibration table disposed above another vibration table includes a front panel and a bottom panel.

AM. The test systems denoted above as AI through AL may include at least one diverter, wherein the at least one diverter is disposed inside the outlet plenum, and wherein the at least one diverter forms a constricted area within the outlet plenum. In such systems, the diverter may be upstream or downstream of any one of the air outlets. AN. The test systems denoted above as AI through AM may include at least one flow control device. The at least one flow control device may be any of a diverter, a damper, a valve, a grill, a louver, an outlet, and an active flow control device.

AO. The test systems denoted above as AI through AN may include a tangential fan as the fan.

AP. The test systems denoted above as AI through AN may include a thermal control element that is disposed within the intake plenum.

AQ. A multiple chamber test system may include a cabinet; at least one door; a plurality of test chambers, wherein each of the test chambers is disposed within the cabinet; a plurality of vibration tables, wherein each test chamber includes at least one vibration table, and wherein each of the vibration tables is accessed through the at least one door; and an air circulator, including at least one intake, an outlet plenum, at least one diverter disposed within the air outlet plenum, and a plurality of air outlets, wherein each test chamber in the plurality of test chambers is associated with at least one air outlet.

AR. The test system denoted above as AQ may include the plurality of test chambers being arranged to form at least one column of test chambers, wherein a vibration table shroud is associated with each test chamber that is above any other test chamber.

AS. The test systems denoted above as AQ and AR may include at least one vibration table shroud, wherein at least one test chamber in the plurality of test chambers is associated with the vibration table shroud.

AT. A system for controlling temperature of a product within a test chamber may include a thermal control element for heating or cooling air, a fan for moving air through the thermal control element and into the test chamber, a temperature sensor within the test chamber, memory having a desired temperature profile stored therein, and a controller coupled with the thermal control element and the temperature sensor. The controller may measure an actual temperature of the test chamber using the temperature sensor, use a proportional integral derivative (PID) function to determine a temperature throttle value based upon the desired temperature profile and the actual temperature, and set a temperature throttle of the thermal control element to the temperature throttle value.

AU. The system denoted above as AT may include the controller implementing a converging algorithm that processes stored temperature throttle values of previous runs against the desired temperature profile, to determine the temperature throttle value.

AV. The systems denoted above as AT or AU may use a PID function to further adjust the temperature throttle, based upon a difference between stored measured temperature values of previous runs and the actual temperature. AW. The systems denoted above as AT, AU or AV may further include a fan throttle for controlling speed of the fan and airflow into the chamber, and the controller may use a PID function to set the fan throttle based upon a difference between stored measured temperature values of the previous runs and the actual temperature.

AX. The systems denoted above as AT through AW may further include a variable flow device for restricting airflow into the chamber and a flow throttle for controlling the variable flow device. The controller may use a PID function to set the flow throttle based upon a difference between stored measured temperature values of the previous runs and the actual temperature.

AY. A system for controlling temperature of a product under test within a test chamber may include a thermal control element for heating or cooling air, a fan for moving air through the thermal control element and into the test chamber, a temperature sensor within the test chamber, and a controller coupled with the thermal control element and the temperature sensor. The controller may include memory and a processor, the and software that when executed by the processor perform the steps of: determining a temperature of the test chamber using the temperature sensor, using a proportional integral derivative (PID) function to determine a temperature throttle value based upon the desired temperature profile and the actual temperature, and setting a temperature throttle of the thermal control element to the temperature throttle value.

AZ. The system denoted above as AY may store a converging algorithm in the memory, that when executed by the processor, performs the step of processing stored temperature throttle values of previous runs against the desired temperature profile to determine an adjusted temperature throttle value for controlling the thermal control elements.

BA. The systems denoted above as AY or AZ may store a PID function in the memory, that when executed by the processor, further adjusts the temperature throttle value based upon a difference between stored measured temperature values of the previous runs and measured temperature of the test chamber.

BB. The systems denoted above as AY, AZ or BA may include a fan throttle for controlling speed of the fan and airflow into the chamber. The memory may further store a PID function, that when executed by the processor, sets the fan throttle based upon a difference between stored measured temperature values of the previous runs and measured temperature of the test chamber.

BC. The systems denoted above as AY through BB may include a variable flow device for restricting airflow into the chamber, and a flow throttle for controlling the variable flow device. The memory may further store a PID function, that when executed by the processor, sets the flow throttle based upon a difference between stored measured temperature values of the previous runs and measured temperature of the test chamber.

BD. A method for controlling temperature of air within a test chamber containing a plurality of test fixtures may include the steps of determining a profile temperature for the test chamber and reading a temperature of the test chamber. If the number of runs of the temperature profile is less than a predefined number, the method stores the chamber temperature in a memory, uses a proportional integral derivative (PID) function to determine a temperature throttle value based upon the profile temperature and the chamber temperature, stores the temperature throttle in the memory and sets the temperature throttle of thermal control elements to the temperature throttle value. If the number of runs of the temperature profile is equal to the predefined number, then the method uses a converging algorithm to determine an adjusted profile, if the number of runs of the temperature profile is greater than the predefined number, the method determines a temperature throttle value from the adjusted profile, uses a PID function to calculate a temperature throttle delta based upon the stored temperature within the memory and the temperature within the chamber and sets the temperature throttle of the thermal control elements based upon the temperature throttle value and the temperature throttle delta.

BE. In the method denoted above as BD, the adjusted profile may include temperature throttle values based upon time.

BF. A software product may include instructions, stored on non-transient computer- readable media, wherein the instructions, when executed by a computer, perform steps for controlling temperature of air within a test chamber containing a plurality of test fixtures. The instructions may include instructions for the steps of determining a profile temperature for the test chamber, reading a temperature of the test chamber, determining if a number of runs of the temperature profile is less than a predefined number. The instructions may include instructions for the steps of (a) storing the temperature in a memory, (b) using a proportional integral derivative (PID) function to determine a temperature throttle value based upon the profile temperature and the temperature; (c) storing the temperature throttle in the memory; and (d) setting a temperature throttle of thermal control elements to the temperature throttle value, steps (a) through (d) being performed when the number of runs of the temperature profile is less than the predetermined number. The instructions may include instructions for using a converging algorithm to determine an adjusted profile when the number of runs of the temperature profile is equal to the predefined number. The instructions may include instructions for (e) determining a temperature throttle value from the adjusted profile, (f) using a PID function to calculate a temperature throttle delta based upon the stored temperature within the memory and the temperature and (g) setting the temperature throttle of the thermal control elements based upon the temperature throttle value and the temperature throttle delta, steps (e) through (g) being performed when the number of runs of the temperature profile is greater than the predefined number.

BG. A software product may include instructions, stored on non-transient computer- readable media, wherein the instructions, when executed by a computer, perform steps for controlling, based upon a desired temperature profile, temperature of a product under test within a test chamber having a temperature throttle, a thermal control element, and a temperature sensor. The instructions may include instructions for the steps of determining a temperature of the test chamber using the temperature sensor; using a proportional integral derivative (PID) function to determine a temperature throttle value based upon the desired profile and the temperature; and setting the temperature throttle of the thermal control element based upon the determined temperature throttle value.

BH. The software product denoted above as BG may include instructions for (a) processing stored temperature throttle values of previous runs against the desired temperature profile to determine an adjusted temperature throttle value, (b) adjusting the improved temperature throttle value based upon a difference between stored measured temperature values of the previous runs, and the temperature, (c) setting a fan throttle to control the speed of a fan that circulated air within the test chamber based upon a difference between stored measured temperature values of the previous runs, and the temperature, and/or instructions for setting a flow throttle of a variable flow control device that restricts the flow of air within the test chamber based upon a difference between stored measured temperature values of the previous runs, and the temperature.

BI. A method for testing a plurality of products may include vibrating at least a first product on a first vibration table within a cabinet, simultaneously vibrating at least a second product on a second vibration table within the cabinet, and simultaneously controlling air temperature of air surrounding the first and second products.

BJ. In the method denoted above as BJ, the steps of vibrating may include utilizing a controller to control the first and second vibration tables, with at least one accelerometer providing acceleration feedback to the controller, and/or the step of controlling may include utilizing the controller to control the temperature, with at least one thermocouple providing temperature measurement feedback to the controller.

BK. In the methods denoted above as BI or BJ, the step of controlling may include controlling an air circulator to control the air temperature, wherein the air circulator includes at least one thermal control element, ducting and at least one fan that cooperate to control the air temperature. BL. In the methods denoted above as BI, BJ or BK, the step of controlling may include cooling the air surrounding the first and second products by utilizing one of a cryogenic liquid, a compressed gas, an evaporator plate, and coils of a mechanical refrigeration unit as the thermal control element. The step of cooling may include cooling the air surrounding the first and second products from a high temperature that is at least 20 degrees Celsius above room temperature, and further comprising flushing an air space around the first and second products with room temperature air before utilizing the thermal control element.

BM. The methods denoted above as BI through BL may include loading at least one of the first and the second product on its respective first or second vibration table while the vibration table being loaded is removed from the cabinet.

BN. The methods denoted above as BI through BM may include sliding the vibration table being loaded out of the cabinet or into the cabinet utilizing one of slides, linear bearings, rollers or wheels. Sliding the vibration table may include sliding the vibration table into the cabinet, and may further include (a) rigidly mounting the vibration table being loaded within the cabinet, and (b) removing the one of slides, linear bearings, rollers or wheels that was utilized to slide the vibration table into the cabinet.

BO. In the methods denoted above as BI through BN, the steps of vibrating may include utilizing fixtures to transmit vibrations from the first and second vibration tables to the first and second products. The fixtures may include one or more elements selected from the group consisting of: manual clamps, magnetic clamps, pneumatic clamps, vacuum clamps, bolts, bars, hinges, clasps, magnets, electromagnets, electric motor actuators, springs, spring loaded devices, and holding blocks. The method may further include utilizing fixtures having one of pneumatic clamps, vacuum clamps, electromagnets and electric motor actuators to automate, at least in part, attachment of one of the first and second products to its respective vibration table.

BP. In the methods denoted above as BI through BO, the steps of vibrating may include (a) utilizing each of the first and second vibration tables while each of said tables is within a respective first and second chamber of the cabinet, and (b) utilizing controllable actuators coupled with each of the first and second tables to generate vibration of the tables and the product. The step of controlling may include (c) utilizing an air circulator to control the air temperature separately for each of the first and second chambers, and (d) controlling air flow vanes to selectively adjust one or both of flow rate and direction of air flowing through at least one of the chambers. The steps of vibrating may include utilizing at least one of the first and second vibration tables while (e) it is mounted along a wall or ceiling of its corresponding chamber, or (f) it is configured non-horizontally within the cabinet. The steps of vibrating may include at least one of the first and second vibration tables while each of said tables is within a respective first and second chamber, the first and second chambers forming a column in the cabinet such that an access door is operable to provide access to both the first and second vibration tables.

BQ. In the methods denoted above as BI through BP, at least one of the steps of vibrating may include utilizing at least one actuator configured to impact its respective vibration table from one side. Also, at least one of the steps of vibrating may include utilizing pneumatic actuators that produce exhaust air, the step of controlling comprising utilizing a screwless skirt that forms a labyrinth seal with a chamber of the respective vibration table, to separate the exhaust air from the air surrounding the respective product.

BR. In the methods denoted above as BI through BQ, the step of controlling may include (a) utilizing an air flow staggered plenum to provide uniform flow to chambers about each of the first and second tables, the plenum being shaped at a back wall of the cabinet, and (b) connecting the plenum to each of the chambers via air outlets, with an area of an air outlet farther from a fan providing the air being smaller than an area of an air outlet nearer to the fan.

BS. In the methods denoted above as BI through BR, a network may be utilized to control the steps of vibrating and the step of controlling.

BT. In the methods denoted above as BI through BS, at least one of the steps of vibrating may include mounting an airtight fixture tray to a frame that vibrates the fixture tray and the product, such that the fixture tray isolates the air surrounding the product from actuator exhaust.

BU. In the methods denoted above as BI through BT, the steps of vibrating may include utilizing each of the first and second vibration tables while each of the tables is within a respective first and second chamber of the cabinet, each of the chambers being adjustable in height within the cabinet, and wherein controlling comprises controlling the air surrounding the first product in the first chamber separately from controlling the air surrounding the second product in the second chamber.

BV. In the methods denoted above as BI through BU, at least one of the steps of vibrating may include utilizing a curved, shaped or weighted table as the first or second vibrating table to vary its frequency response when actuated.

BW. In the methods denoted above as BI through BW, the step of controlling may include circulating the air surrounding the first and second products with one of a tangential fan, a plurality of tangential fans, and a centrifugal blower.

[0121] The foregoing discussion has been presented for purposes of illustration and description. The descriptions herein are intended as illustrative and not limiting. Consequently, variations and modifications commensurate with the above teachings, within the skill or knowledge of the relevant art, should be considered within the scope of the appended claims. The embodiments described hereinabove are further intended to explain the best mode presently known of practicing the invention and to enable others skilled in the art to utilize the invention in such or in other embodiments and with various modifications required by a particular application or use. It is intended that the appended claims be construed to include alternative embodiments to the extent permitted by the prior art.