CLAIM OF PRIORITY

[0001] This application claims priority to U.S. Patent Application No. 15/380,582 filed on December 15, 2016, the entire contents of which are hereby incorporated by reference.

BACKGROUND

[0002] The following description relates to the communication of characterization data between electrically connected components.

[0003] Fuel metering units (FMU) have inherent deviation from desired flow schedules as a result of accuracy limitations in variable differential transformer

(VDT) demodulation, pressure droop, friction, fluid leakages and other influences. Various schemes have been invented to counter these effects and improve overall accuracy, but since these schemes usually only address a particular effect there is a limitation to their overall effectiveness.

[0004] Previous techniques used to transfer such data have been implemented as memory devices or personality modules in the FMU that are interrogated over a communications bus by a full authority digital engine controller (FADEC). Such solutions require sophisticated electronic circuit assemblies that are capable of surviving in harsh engine environments yet still are able to perform the necessary communications. FADECs are also often limited in the input/output resources needed to communicate with such sophisticated memory devices or personality modules. Some such solutions also add to the cost and complexity of the wiring between the FADEC and the

FMU to enable communications between such solutions and the FADEC. These factors can severely reduce how much coded information can be made available to the FADEC, and as a result can reduce the usefulness of a FMU characterization correction scheme.

SUMMARY

[0005] In general, this document describes communication of

characterization data between electrically connected components.

[0006] In a first aspect, an identification system comprises a first component comprising a first resistor, and a second resistor, a second component comprising a sensor configured to sense a voltage difference between a first bus and a second bus, and a selector signal output port configured to provide a first selector signal and a second selector signal, and a third component comprising a switching network configured to electrically connect the second bus to the first bus across one or both of the first resistor and the second resistor in response to the first selector signal, and electrically connect the second bus to the first bus across a different one of the first resistor or the second resistor in response to the second selector signal.

[0007] In a second aspect, the identification system of aspect 1 , wherein the first component further comprises a first port in direct electrical

communication with the first resistor and not in direct electrical communication with the second resistor; a second port in direct electrical communication with the second resistor and not in direct electrical communication with the first resistor, and a third port in direct parallel electrical communication with the first resistor and the second resistor, and the first bus is in electrical communication with the third port, and the switching network is further configured to electrically connect the second bus to the first port in response to the first selector signal, and electrically connect the second bus to the second port in response to the second selector signal.

[0008] In a third aspect, the identification system of aspect 1 or 2, wherein the first component further comprises a first port and a second port in electrical communication with the first port across the first resistor in series electrical connection with the second resistor, and the switching network is further configured to electrically bypass electrical communication between the first port and the second port around one of the first resistor or the second resistor in response to the first selector signal, and not bypass electrical

communication around the first resistor or the second resistor in response to the second selector signal.

[0009] In a fourth aspect, the identification system of any one of aspects 1 to 3, wherein the first component further comprises a first port and a second port in electrical communication with the first port across a first electrical path in parallel with a second electrical path, the first electrical path comprising the first resistor in series electrical connection with a first switch of the switching network, and the second electrical path comprising the second resistor in series electrical connection with a second switch of the switching network, and the switching network is further configured to close the first switch and open the second switch in response to the first selector signal, and open the first switch and close the second switch in response to the second selector signal. [0010] In a fifth aspect, the identification system of any one of aspects 1 to

4, wherein the second component further comprises a current source configured to provide a current between the first bus and the second bus.

[0011] In a sixth aspect, the identification system of any one of aspects 1 to

5, wherein at least one of the first resistor and the second resistor is a programmable resistor programmed to provide a selected resistance.

[0012] In a seventh aspect, the identification system of any one of aspects 1 to 6, wherein the third component is located remotely from the first component.

[0013] In an eighth aspect, the identification system of any one of aspects 1 to 7, wherein the second component comprises the third component.

[0014] In a ninth aspect, the identification system of any one of aspects 1 to

8, wherein the first component is selected from a group comprising a fuel metering unit, an actuator, a valve, and a line replaceable unit, and the second component is an engine controller.

[0015] In a tenth aspect, the identification system of any one of aspects 1 to

9, wherein the first component further comprises a line replaceable unit configured to receive a driver signal, the selector signal output port configured to provide the driver signal as at least one of the first selector signal and the second selector signal.

[0016] In an eleventh aspect, the identification system of any one of aspects 1 to 10, wherein the selector signal output port is further configured to provide a third selector signal, and the switching network is configured to electrically connect the second bus to the first bus across one of the first resistor and the second resistor in response to the first selector signal, electrically connect the second bus to the first bus across a different one of the first resistor or the second resistor in response to the second selector signal, and electrically connect the second bus to the first bus across both the first resistor and the second resistor in response to a third selector signal.

[0017] In a twelfth aspect, a method of identifying a component comprises providing a first bus and a second bus, providing a first selector signal at a selector port, connecting, based on the first selector signal, at least one or both of a first resistor and a second resistor between the first bus and the second bus, measuring a first resistance between the first bus and the second bus to determine a first resistance value, providing a second selector signal at the selector port, connecting, based on the second selector signal, a different one of the first resistor and the second resistor between the first bus and the second bus, and measuring a second resistance between the first bus and the second bus to determine a second resistance value.

[0018] In a thirteenth aspect, the method of aspect 12 further comprises determining an identity based on the first resistance value and the second resistance value.

[0019] In a fourteenth aspect, the method of aspects 12 or 13 further comprises providing a collection of known resistance values and

corresponding identity values, comparing the first resistance to the collection of known resistance values to identify a first corresponding identity value, and comparing the second resistance to the collection of known resistance values to identify a second corresponding identity value, wherein the identity is based on the first corresponding identity value and the second corresponding identity value.

[0020] In a fifteenth aspect, the method of any one of aspects 12 to 14 further comprises identifying a first coefficient value based on the first resistance value, and identifying a second coefficient value based on the second resistance value, wherein the identity is based on an output value provided by a mathematical formula comprising the first coefficient value and the second coefficient value.

[0021] In an sixteenth aspect, the method of any one of aspects 12 to 15, wherein a first component provides the first resistor and the second resistor, a second component provides the selector signal to the first component and measures the first resistance and the second resistance, and the second component determines an identity of the first component based on the first resistance value and the second resistance value.

[0022] In a seventeenth aspect, the method of aspect 16, wherein the second component is located remotely from the first component.

[0023] In an eighteenth aspect, the method of any one of aspects 12 to 17 wherein at least one of the first resistor and the second resistor is a programmable resistor, and the method further comprises programming the programmable resistor to provide a selected one of the first resistance and the second resistance.

[0024] In a nineteenth aspect, the method of any one of aspects 12 to 18 further comprises providing a third selector signal at the selector port, connecting, based on the third selector signal, both the first resistor and the second resistor between the first bus and the second bus, and measuring a third resistance between the first bus and the second bus to determine a third resistance value, wherein connecting, based on the first selector signal, at least one or both of the first resistor and the second resistor between the first bus and the second bus comprises connecting one of the first resistor and the second resistor between the first bus and the second bus.

[0025] In a twentieth aspect, the method of any one of aspects 12 to 19 further comprises providing at least one of the first selector signal and the second selector signal as a driver signal to a line replaceable unit, and driving operation of the line replaceable unit based on the driver signal.

[0026] The systems and techniques described here may provide one or more of the following advantages. First, a system can identify components of a system to a control module. Second, the system can identify remotely located components. Third, the system can provide identifying information using electronic components that are sufficiently robust to withstand harsh operating environments, such as engine compartments. Fourth, the system can provide such identification with a small number of wires. Fifth, the system can enable commercial or otherwise "off the shelf" engine controllers to identify and/or characterize remotely located fuel management units or other components. Sixth, the system can be manufactured with greater simplicity and economy than other systems that provide similar functionality. Seventh, the system can be constructed with less weight and/or volume than other systems that provide similar functionality. [0027] The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

[0028] FIG. 1 is a schematic diagram that shows an example of a system for communication of characterization data.

[0029] FIG. 2 is a schematic diagram that shows another example of a system for communication of characterization data.

[0030] FIG. 3 is a schematic diagram that shows another example of a system for communication of characterization data.

[0031] FIG. 4 is a schematic diagram that shows another example of a system for communication of characterization data.

[0032] FIG. 5 is a schematic diagram that shows another example of a system for communication of characterization data.

[0033] FIG. 6 is a flow diagram of an example process for the

communication of characterization data.

DETAILED DESCRIPTION

[0034] This document describes systems and techniques for the communication of characterization data between electrically connected components. Generally speaking, fuel metering units (FMU) have inherent deviation from desired flow schedules as a result of accuracy limitations in variable differential transformer (VDT) demodulation, pressure droop, friction, fluid leakages, and other influences. [0035] Still generally speaking, systems to characterize the cumulative effects of some or all of the contributors to inaccuracy for a particular FMU can be used to allow a controlling device such as a full authority digital engine controller (FADEC) or electronic engine controller (EEC) to compensate for a particular FMU's inaccuracies and provide for more accurate overall system performance. For example, if fuel flow of a particular FMU, for a given set of conditions, is known to be 12.5 pph (pounds per hour) low, the FADEC could be configured to increase its command at that point an additional 12.5 pph to account for the inaccuracy.

[0036] Still generally speaking, resistor networks can be used in personality modules to provide two or more identifiable resistances, and these resistances can be used to identify or characterize an associated component such as a FMU. While it can be challenging and costly to design complex electronic assemblies (e.g., static computer memory modules) that can function in the harsh environments such as those encountered by FMUs, resistor networks such as those described herein can be suitably designed to function in such harsh environments much more easily and economically than other more complex solutions. Such personality modules can be electrically connected to and interrogated by a control module, such as an engine controller, to read the two or more resistances and determine a characterization value conveyed by the resistances that can be used, for example, to compensate for a particular FMU's performance characteristics.

[0037] In addition to being challenging and costly to design complex electronic assemblies, some such assemblies may require the use of complex interconnections in order to communicate characterization data (e.g., multiple parallel conductors, EMI shielding, controlled spacing/twisting of conductors). Some such assemblies may require relatively larger and heavier housings to accommodate levels of cooling and/or vibration isolation needed to protect such complex electronic assemblies, in addition to being able to accommodate the relatively larger electronic assemblies themselves. In the following examples, multiple identifiable resistances are multiplexed over relatively simpler, cheaper, and more robust electrical busses (e.g., using as few as three wires).

[0038] FIG. 1 is a schematic diagram that shows an example system 100 for communication of characterization data. The system 100 includes a personality module 1 10 and a control module 150. The personality module 1 10 and the control module 150 are in electrical communication by a collection of buses 190a-190c.

[0039] The personality module 1 10 is a switching network configured to electrically connect the bus 160b to the bus 160a across one or both of a resistor 1 14 and a resistor 1 16 in response to a selector signal in a first state (e.g., off), and electrically connect the bus 190b to the bus 190a across a different one of the resistor 1 14 or the resistor 1 16 (e.g., bypassing the resistor 1 16) in response to the selector signal being in a second state (e.g., on). In some embodiments, the personality module 1 10 can be a portion of or associated with (e.g., attached to) a fuel metering unit (FMU), a line

replaceable unit (LRU) (e.g., actuator, torque motor, solenoid, solenoid valve, servo valve, resistance temperature detector (RTD), thermometer, linear or rotary variable differential transformer (LVDT, RVDT), resolver, strain gauge, switch, piezo), or any other appropriate component that can be associated with one or more unique characterization values (e.g., serial number, make and/or model identifier, calibration value, offset value).

[0040] In some embodiments, the control module 150 can be a full authority digital engine controller (FADEC), an engine control unit (ECU), an electronic engine controller (EEC), or any other appropriate electronic controller. In some implementations, the system 100 can be used as part of an engine system.

[0041] The control module 150 includes a current source 152 and a voltage sensor 154. In general, the current source 152 is used to provide electrical current to resistive loads (which will be described below) and the voltage sensor 154 senses the voltage difference between the bus 190a and 190b, developed by the current across the resistive load(s). By knowing the amount of current being provided by the current source 152 and the voltage measured by the voltage sensor 154, the resistance of the resistive loads can be determined (e.g., using Ohm's law).

[0042] The control module 150 includes a collection of ports 160a-160c. The ports 160a-160c provide electrical connections between the control module 150 and the buses 190a-190c. A first side of the current source 152 is connected in parallel with a first side of the voltage sensor 154 to the bus 190a by the port 160a. A second side of the current source 152 is connected in parallel with a second side of the voltage sensor 154 to the bus 190b by the port 160b. The bus 190a is in electrical communication with the bus 190b through a resistor 1 14 arranged in series with a resistor 1 16.

[0043] The port 160c selectively provides a selector signal (e.g., a control signal, a switching signal) to the bus 190c. The bus 190c carries the selector signal to a controllable switch 1 12. In some embodiments, the switch 1 12 can be a transistor (e.g., BJT, FET, MOSFET), a relay, or any other appropriate device that can controllably switch an electrical circuit. The switch 1 12 is arranged to controllably provide an electrical shunt around the resistor 1 16.

[0044] In such an arrangement, when the switch 1 12 is open (e.g., the selector signal on bus 190c is in a first state), the bus 190a is connected to the bus 190b through both the resistor 1 14 and the resistor 1 16 in series. In such a configuration, the voltage sensed at the voltage sensor 154 is a product of the sum of the resistances of the resistor 1 14 and the resistor 1 16. However, when the switch is closed (e.g., the selector signal on bus 190c is in a second state), the bus 190a is connected to the bus 190b through the resistor 1 14 and the shunt provided by the switch 1 12, bypassing the resistor 1 16. In such a configuration, the voltage sensed at the voltage sensor 154 is a product of the resistance of the resistor 1 14 alone.

[0045] As such, the configuration of the system 100 can cause two different resistance values to appear at voltage sensor 154 by toggling the selector signal being provided by the port 160c. For example, the resistor 1 14 can be a 10K ohm resistor and the resistor 1 16 can be a 250 ohm resistor. When the selector signal from the port 160c is in the first state, the switch 1 12 will be open, and current will flow from the port 160a through the resistor 1 14 and the resistor 1 16 such that a 10,250 ohm resistance is presented across the voltage sensor 154. When the selector signal from the port 160c is in the second state, the switch 1 12 will be closed, and current will flow from the port 160a through the resistor 1 14 and around the resistor 1 16 such that a 10,000 ohm resistance is presented across the voltage sensor 154.

[0046] In some implementations, the multiplexed resistance values of the resistors 1 14-1 16 can be read directly to provide characterization information. For example, the identity module 1 10 may be associated with an FMU that has been measured as deviating from a baseline flow by 12%. The resistor 1 14 may be used to indicate the tens place of the 12% figure and the resistor 1 16 may be used to indicate the ones place. For example, a 10 ohm resistor and 2 ohm resistor can be used to represent 10% and 2% respectively (e.g., 10%+2%=12%).

[0047] In another example, the values of the resistors 1 14 and 1 16 may be used by the control module 150 as two separate variables in a polynomial equation. For example, the resistor 1 14 can have a resistance of Ri ohms and the resistor 1 16 can have a resistance of R2 ohms. An adjustment factor for an FMU identified by the identity module 1 10 can be determined by measuring Ri and R2 and then processing those values through algebraic or other types of equations such as "y = Rix + R2" or "y = x ^R1 + B ^R2 " where x can be the nominal fuel flow and y can be the corrected fuel flow.

[0048] In another example, the values of the resistors 1 14 and 1 16 may be used by the control module 150 to identify the identity module 1 10 (e.g., and an FMU associated with the identity module 1 10). For example, an FMU to be characterized by the identity module 1 10 might be a "Series 6, Model 9" FMU. The resistor 1 14 can be configured as a 6K ohm resistor (e.g., to represent the series number), and the resistor 1 16 can be configured as a 9K ohm resistor (e.g., to represent the model number). When the control signal at the port 160c is toggled, a 9K ohm load and a 15K ohm load (e.g., 9K + 6K in series) can be selectably presented at the voltage sensor 154. The control module 150 process these values to determine the series number (e.g., rounding the value of 9K/1000 = 9) and the model (e.g., rounding (15K-9K)/1000 = 6). Based on the determined series and model numbers, a corresponding calibration or other adjustment can be made by the control module 150 for the device associated with the identity module 1 10 (e.g., a "Series 6, Model 9" FMU may require 500mA for activation and flow of 10ml per second, whereas a "Series 4, Model 3" FMU may require 100mA for activation and flow of 20ml_ per second).

[0049] In another example, the values of the resistors 1 14 and 1 16 may be used by the control module 150 to perform a table lookup. For example, the resistor 1 14 can be configured as a 5K ohm resistor, and the resistor 1 16 can be configured as a 7K ohm resistor. The control module can toggle the selector signal at the port 160c to determine both resistances, and obtain a row value of 5 (e.g., 5K/1000) and a column value of 7 (e.g., 7K/1000). The control module 150 can use these values to perform a table lookup at row 5, column 7, to determine an identifier, calibration value, or any other appropriate type of information that can be used to characterize the FMU or other device associated with the identity module 1 10. In some implementations, the values of the resistors 1 14 and 1 16 may be used as indices to a full compensation table.

[0050] FIG. 2 is a schematic diagram that shows an example system 200 for communication of characterization data. The system 200 includes a personality module 210 and a control module 250. The personality module 210 and the control module 250 are in electrical communication by a collection of buses 290a-290e.

[0051] The personality module 210 is a switching network configured to electrically connect the bus 260b to the bus 260a across a resistor 214 in response to a selector signal in a first state (e.g., off), and electrically connect the bus 260b to the bus 260a across a resistor 216 in response to the selector signal being in a second state (e.g., on). In some embodiments, the personality module 210 can a portion of or associated with (e.g., attached to) a fuel metering unit (FMU) , an LRU, or any other appropriate component that can be associated with one or more unique characterization values (e.g., serial number, make and/or model identifier, calibration value, offset value).

[0052] In some embodiments, the control module 250 can be a full authority digital engine controller (FADEC), an engine control unit (ECU), an electronic engine controller (EEC), or any other appropriate electronic controller. In some implementations, the system 200 can be used as part of an engine system.

[0053] The control module 250 includes a current source 252 and a voltage sensor 254. In general, the current source 252 is used to provide electrical current to resistive loads (which will be described below) and the voltage sensor 254 senses the voltage difference between the bus 290a and 290b, developed by the current across the resistive load(s). By knowing the amount of current being provided by the current source 252 and the voltage measured by the voltage sensor 254, the resistance of the resistive loads can be determined (e.g., using Ohm's law).

[0054] The control module 250 includes a collection of ports 260a-260e. The ports 260a-260e provide electrical connections between the control module 250 and the buses 290a-290e. A first side of the current source 252 is connected in parallel with a first side of the voltage sensor 254 to the bus 290a by the port 260a. A second side of the current source 252 is connected in parallel with a second side of the voltage sensor 254 to the bus 290b by the port 260b. The bus 290a is in electrical communication with the bus 290b through a resistor 214 arranged in parallel with a resistor 216.

[0055] The port 260c selectively provides a selector signal (e.g., a control signal, a switching signal) to the bus 290c. The bus 290c carries the selector signal to a controllable switch 212. The switch 212 is arranged to alternatingly activate a collection of controllable switches 213a-213c. In some

embodiments, the switches 212 and 213a-213c can be transistors, relays, or any other appropriate devices that can controllably switch electrical circuits. The port 260d provides a voltage on the bus 290d that is switched by the switches 212 and 213a-213c. The port 260e provides a common (e.g., ground) for the bus 290e and the switches 212 and 213a.

[0056] In such an arrangement, when the switch 212 is open (e.g., the selector signal on bus 290c is in a first state), current from the bus 290d is not able to flow through the switch 212 to the bus 290e (e.g., ground), and a voltage is presented to the switch 213a and the switch 213b, closing both of the switches 213a and 213b. When the switch 213b is closed, a current flow path 224 is formed between the bus 290a and the bus 290b through the resistor 214. When the switch 213a is closed, current from the bus 290d is shunted to the bus 290e (e.g., shorted), and a voltage is absent from the switch 213c, opening the switch 213c and preventing current from flowing along a current path 226. In this configuration, the voltage sensed at the voltage sensor 254 is a product of the resistance of the resistor 214 but not the resistor 216.

[0057] When the switch 212 is closed (e.g., the selector signal on bus 290c is in a second state), current from the bus 290d is able to flow through the switch 212 to the bus 290e (e.g., shorted), and a voltage is not presented to the switch 213a and the switch 213b, opening both of the switches 213a and 213b. When the switch 213b is open, the current flow path 224 is blocked. When the switch 213a is open, current from the bus 290d is blocked from the bus 290e, and a voltage is presented to the switch 213c, closing the switch 213c and permitting current to flowing along the current path 226 from the bus 290a through the resistor 216 to the bus 290b. In this configuration, the voltage sensed at the voltage sensor 254 is a product of the resistance of the resistor 216 but not the resistor 214.

[0058] In some embodiments, the configuration of the example system 200 can permit the independent reading of two independent resistors. For example, the resistor 214 can be a 1 k ohm resistor to represent a first characterization value, and a second different characterization value can be represented by a 2k ohm resistor as the resistor 216. As such, the

configuration of the system 200 can cause two different resistance values to appear at voltage sensor 254 by toggling the selector signal being provided by the port 260c. In some embodiments, the values of the resistors 214 and 216 can be used in at least the ways that were described previously for the resistors 1 14 and 1 16 of FIG. 1 .

[0059] FIG. 3 is a schematic diagram that shows another example of a system 300 for communication of characterization data. The system 300 includes the example personality module 210 and the example control module 250 of the example system 200 of FIG. 2. However, in the system 300, the resistors 214 and 216 of the system 200 have been replaced by a

programmable resistor 314 and a programmable resistor 316. The

programmable resistors 314 and 316 may be configured through a serial programming interface (SPI) 380. In some implementations, configuration of the resistors 314 and 316 may be performed at the time of manufacture.

[0060] In various embodiments, the resistor 314, the resistor 316, and/or any other resistor described in this specification can be a fixed value or an adjustable value (e.g., programmable, trimmable, adjustable) resistor. For example, an FMU to be characterized by the personality module 210 may flow 120 pph too low for a predetermined low flow rate calibration point, and may flow 75 pph too low for a predetermined high flow rate calibration point. As such, a user may access the SPI 380 to program the resistor 314 with a value of 120k ohms to represent the deviation from the low flow rate, and program the resistor 316 with a value of 75K ohms to represent the deviation from the high flow rate. In some embodiments, the values of the resistors 314 and 316 can be used in at least the ways that were described previously for the resistors 1 14 and 1 16 of FIG. 1 .

[0061] FIG. 4 is a schematic diagram that shows another example of a system 400 for communication of characterization data. The system 400 includes a personality module 410 and a control module 450. The personality module 410 and the control module 450 are in electrical communication by a collection of buses 490a-490e.

[0062] The personality module 410 is a switching network configured to electrically connect the bus 490b to the bus 490a across a resistor 414 in response to a selector signal in a first state (e.g., off), and electrically connect the bus 490b to the bus 490a across a resistor 416 in response to the selector signal being in a second state (e.g., on). In some embodiments, the personality module 410 can be a portion of or associated with (e.g., attached to) a fuel metering unit (FMU), an LRU, or any other appropriate component that can be associated with one or more unique characterization values (e.g., serial number, make and/or model identifier, calibration value, offset value).

[0063] In some embodiments, the control module 450 can be a full authority digital engine controller (FADEC), an engine control unit (ECU), an electronic engine controller (EEC), or any other appropriate electronic controller. In some implementations, the system 200 can be used as part of an engine system. [0064] The control module 450 includes a current source 452 and a voltage sensor 454. In general, the current source 452 is used to provide electrical current to resistive loads (which will be described below) and the voltage sensor 454 senses the voltage difference between the bus 490a and 490b, developed by the current across the resistive load(s). By knowing the amount of current being provided by the current source 452 and the voltage measured by the voltage sensor 454, the resistance of the resistive loads can be determined (e.g., using Ohm's law).

[0065] The control module 450 includes a collection of ports 460a-460e. The ports 460a-460e provide electrical connections between the control module 450 and the buses 490a-490e. A first side of the current source 452 is connected in parallel with a first side of the voltage sensor 454 to the bus 490a by the port 460a. A second side of the current source 452 is connected in parallel with a second side of the voltage sensor 454 to the bus 490b by the port 460b. The bus 490a is in electrical communication with the bus 490b through a resistor 414 and a controllable switch 413a arranged in parallel with a resistor 416 and a controllable switch 413b included in the personality module 410. In some embodiments, the switches 213a-213b can be transistors, relays, or any other appropriate devices that can controllably switch electrical circuits.

[0066] The personality module 410 also includes a shut-off solenoid 420. The shut off solenoid includes a coil 422 with a winding 424a and a winding 424b. In some embodiments, an armature (not shown) can be actuated by energizing one or both of the windings 424a-424b. The winding 424a is energized when the control module 450 provides an appropriate electrical current at the port 460d, and the current is carried to the winding 424a by the bus 490d. The current flows through the winding 424a to the bus 490e, which is in electrical communication with the port 460e (e.g. , common, ground). The winding 424b is energized when the control module 450 provides an appropriate electrical current at the port 460c, and the current is carried to the winding 424b by the bus 490c. The current flows through the winding 424b to the bus 490e, which is in electrical communication with the port 460e.

[0067] The signal provided to the winding 424a is also provided to the switch 413a, and the signal provided to the winding 424b is also provided to the switch 413b. In such an arrangement, a control signal provided by the control module to energize the winding 424a can also serve as selector signal (e.g., a control signal, a switching signal) to activate the controllable switch 413a. Similarly, a control signal provided by the control module to energize the winding 424b can also serve as selector signal to activate the controllable switch 213a.

[0068] In such an arrangement, when the control module 450 energizes the winding 424a (e.g., the selector signal is in a first state), the switch 413a closes and current from the bus 490a is able to flow along a current path 444 through the switch 413a and the resistor 414 to the bus 490b. In this configuration, the voltage sensed at the voltage sensor 454 is a product of the resistance of the resistor 414 but not the resistor 416.

[0069] When the control module 450 energizes the winding 424b (e.g., the selector signal is in a second state), the switch 413b closes and current from the bus 490a is able to flow along a current path 446 through the switch 413b and the resistor 416 to the bus 490b. In this configuration, the voltage sensed at the voltage sensor 454 is a product of the resistance of the resistor 416 but not the resistor 414.

[0070] When both of the windings 424a and 424b are energized (e.g., the selector signal is in a third state), both of the switches 413a and 413b are closed and current will flow along the current path 444 in parallel with the current path 446. In this configuration, the voltage sensed at the voltage sensor 454 is a product of the resistance of the resistor 414 in parallel with the resistor 416.

[0071] In some implementations, the control module 450 can control the timing at which the voltage sensor 454 is read to coincide with the control of the solenoid 420 to determine if the voltage reading corresponds to the influence of the resistor 414, the resistor 416, or both in parallel. In some implementations, the control module 450 can read the resistance values dynamically (e.g., during operation of an engine in which the solenoid 420 is a component). In some implementations, the control module 450 can read the resistance values at a predetermined time (e.g., a self-check routine prior to engine startup). In some embodiments, the values of the resistors 414 and 416 can be used in at least the ways that were described previously for the resistors 1 14 and 1 16 of FIG. 1 .

[0072] In some implementations, any appropriate form of line replaceable unit (LRU) can be used in addition to or in place of the shut-off solenoid 420. Examples of LRU's can include torque motors, solenoids, solenoid valves, servo valves, resistance temperature detectors (RTD), thermometers, linear or rotary variable differential transformers (LVDT, RVDT), resolvers, strain gauges, switches, piezos, or any other appropriate component that can be actuated by one or more control signals that can also be provided to at least one of two or more resistors configured to provide resistance values that can identify or characterize the FMU or a component that includes the FMU.

[0073] In some embodiments, the configuration of the example system 400 can permit the control module 450 to independently read two independent resistors based on control signals already being provided by the control module 450 (e.g., no dedicated control ports or buses are needed to actuate the switching network). Although a solenoid 420 is shown and described in the illustrated example, any appropriate device that can receive two or more control signals can be used (e.g., up/down motor, high/low headlight beams, left/right steering actuator, increment/decrement logic signals).

[0074] FIG. 5 is a schematic diagram that shows another example of a system for communication of characterization data. The system 500 includes a personality module 510 and a control module 550. The personality module 510 and the control module 550 are in electrical communication through an adapter module 570. The control module is in electrical communication with the adapter module 570 by a collection of buses 590a-590e, and the personality module 510 is in electrical communication with the adapter module by a collection of buses 590f-590h.

[0075] The adapter module 570 is a switching network configured to electrically connect the bus 590b to the bus 590a across a resistor 514 in response to a selector signal in a first state (e.g., off), and electrically connect the bus 590b to the bus 590a across a resistor 516 in response to the selector signal being in a second state (e.g., on). In some embodiments, the personality module 510 can be a portion of or associated with (e.g., attached to) a fuel metering unit (FMU) , an LRU, or any other appropriate component that can be associated with one or more unique characterization values (e.g., serial number, make and/or model identifier, calibration value, offset value). In some embodiments, the values of the resistors 514 and 516 can be used in at least the ways that were described previously for the resistors 1 14 and 1 16 of FIG. 1 .

[0076] In some embodiments, the control module 550 can be a full authority digital engine controller (FADEC), an engine control unit (ECU), an electronic engine controller (EEC), or any other appropriate electronic controller. In some implementations, the system 500 can be used as part of an engine system.

[0077] In some embodiments, the adapter module 570 can be located proximal to the personality module 510 and remote from the control module 550 (e.g. , the personality module 510 and the adapter module 570 can be located near an engine, and the control module 550 can be located away from the engine). In some embodiments, the adapter module 570 can be located proximal to the control module 550 and remote from the personality module 510 (e.g. , the personality module 510 can be located near an engine, and the adapter module 570 and the control module 550 can be located away from the engine). [0078] The control module 550 includes a current source 552 and a voltage sensor 554. In general, the current source 552 is used to provide electrical current to resistive loads (which will be described below) and the voltage sensor 554 senses the voltage difference between the bus 590a and 590b, developed by the current across the resistive load(s). By knowing the amount of current being provided by the current source 552 and the voltage measured by the voltage sensor 554, the resistance of the resistive loads can be determined (e.g., using Ohm's law).

[0079] The control module 550 includes a collection of ports 560a-560e. The ports 560a-560e provide electrical connections between the control module 550 and the buses 590a-590e. A first side of the current source 552 is connected in parallel with a first side of the voltage sensor 554 to the bus 590a by the port 560a. A second side of the current source 552 is connected in parallel with a second side of the voltage sensor 554 to the bus 590b by the port 560b.

[0080] The adapter module 570 includes a collection of ports 560f-560h. The ports 560f-560h provide electrical connections between the adapter module 570 and the buses 590f-590h. The bus 590f is in electrical communication with the bus 590h through a resistor 514, and the bus 590f is in electrical communication with the bus 590g though a resistor 516.

[0081] The port 560c selectively provides a selector signal (e.g., a control signal, a switching signal) to the bus 590c. The bus 590c carries the selector signal to a controllable switch 512. The switch 512 is arranged to

alternatingly activate a collection of controllable switches 513a-513c. In some embodiments, the switches 512 and 513a-513c can be transistors, relays, or any other appropriate devices that can controllably switch electrical circuits. The port 560d provides a voltage on the bus 590d that is switched by the switches 512 and 513a-513c. The port 560e provides a common (e.g., ground) for the bus 590e and the switches 512 and 513a.

[0082] In such an arrangement, when the switch 512 is open (e.g., the selector signal on bus 590c is in a first state), current from the bus 590d is not able to flow through the switch 512 to the bus 590e (e.g., ground), and a voltage is presented to the switch 513a and the switch 513b, closing both of the switches 513a and 513b. When the switch 513b is closed, a current flow path 524 is formed between the bus 590a and the bus 590b through the resistor 514. When the switch 513a is closed, current from the bus 590d is shunted to the bus 590e (e.g., shorted), and a voltage is absent from the switch 513c, opening the switch 513c and preventing current from flowing along a current path 526. In this configuration, the voltage sensed at the voltage sensor 554 is a product of the resistance of the resistor 514 but not the resistor 516.

[0083] When the switch 512 is closed (e.g., the selector signal on bus 590c is in a second state), current from the bus 590d is able to flow through the switch 512 to the bus 590e (e.g., shorted), and a voltage is not presented to the switch 513a and the switch 513b, opening both of the switches 513a and 513b. When the switch 513b is open, the current flow path 524 is blocked. When the switch 513a is open, current from the bus 590d is blocked from the bus 590e, and a voltage is presented to the switch 513c, closing the switch 513c and permitting current to flowing along the current path 526 from the bus 590a through the resistor 516 to the bus 590b. In this configuration, the voltage sensed at the voltage sensor 554 is a product of the resistance of the resistor 516 but not the resistor 514.

[0084] In some embodiments, the configuration of the example system 500 can permit the independent reading of two independent resistors. For example, the resistor 514 can be a 15k ohm resistor to represent a first characterization value, and a second different characterization value can be represented by a 22k ohm resistor as the resistor 516. As such, the configuration of the system 500 can cause two different resistance values to appear at voltage sensor 554 by toggling the selector signal being provided by the port 560c.

[0085] FIG. 6 is flow chart that shows an example of a process 600 for the communication of characterization data. In some implementations, the process

600 can be performed by the example systems 100-500 of FIGs. 1 -5.

[0086] At 610, a first bus and a second bus are provided. For example, the system 100 includes the bus 190a and the bus 190b. In another example, the system 500 includes the bus 590a and the bus 590b.

[0087] At 620, a first selector signal is provided at a selector port. For example, the control module 100 can provide a selector signal in a first state

(e.g., off) at the port 160c. In another example, the control module 500 can provide a selector signal in a first state (e.g., off) at the port 560c.

[0088] At 630, at least one or both of a first resistor and a second resistor are connected between the first bus and the second bus based on the first selector signal. For example, in the example system 100, the resistors 1 14 and 1 16 are connected between the bus 190a and the bus 190b when the selector signal is in the first state (e.g., off). In the example system 500, the resistor 514 is connected between the bus 590a and the bus 590b when the selector signal is in the first state (e.g., off).

[0089] At 640, a first resistance is measured between the first bus and the second bus to determine a first resistance value. For example, the system 100 develops a resistance, between the bus 190a and the bus 190b, that is based on a sum of the resistances of the resistors 1 14 and 1 16 when the selector signal is in the first state (e.g., off). In the example system 500, a resistance based on the resistance of the resistor 514 is developed between the bus 590a and the bus 590b when the selector signal is in the first state (e.g., off).

[0090] At 650, a second selector signal is provided at the selector port. For example, the control module 100 can provide a selector signal in a second state (e.g., on) at the port 160c. In another example, the control module 500 can provide a selector signal in a second state (e.g., on) at the port 560c.

[0091] At 660, a different one of the first resistor and the second resistor are connected between the first bus and the second bus based on the second selector signal. For example, in the example system 100, the resistor 1 16 is bypassed through the switch 1 12, leaving only the resistor 1 14 connected between the bus 190a and the bus 190b when the selector signal is in the second state (e.g. , on). In the example system 500, the resistor 516 is connected between the bus 590a and the bus 590b when the selector signal is in the second state (e.g., on). [0092] At 670, a second resistance is measured between the first bus and the second bus to determine a second resistance value. For example, the system 100 develops a resistance, between the bus 190a and the bus 190b, that is based on the resistance of the resistor 1 14 when the selector signal is in the second state (e.g., on). In the example system 500, a resistance based on the resistance of the resistor 516 is developed between the bus 590a and the bus 590b when the selector signal is in the second state (e.g., on).

[0093] In some implementations, the process 600 can include determining an identity based on the first resistance value and the second resistance value. For example, the resistances of the resistors 1 14 and 1 16 can be selected to indicate a serial number, a make/model number, a calibration offset value, or any other value that can be represented directly or indirectly by two numerical resistance values.

[0094] In some implementations, the process 600 can include providing a collection of known resistance values and corresponding identity values, comparing the first resistance to the collection of known resistance values to identify a first corresponding identity value, and comparing the second resistance to the collection of known resistance values to identify a second corresponding identity value, wherein the identity is based on the first corresponding identity value and the second corresponding identity value. For example, the control module 550 can be preprogrammed with a collection of lookup values that correspond to predetermined resistance ranges. In examples such as this, resistances between 8k ohms and 12k ohms can be used to represent a product model "X", and resistances for the resistor 514 between 18k ohms and 22k ohms can be used to represent a product model "Y". Similarly, resistances for the resistor 516 between 2k ohms and 4k ohms can be used to represent a product series "A", resistances between 5k ohms and 7k ohms can be used to represent a product series "B". As such, a predetermined combination of the resistors 514 and 516 can be used in the personality module 510 to represent an FMU that is a "Model X, Series A", a "Model X, Series B", a "Model Y, Series A", or a "Model Y, Series B" type FMU.

[0095] In some implementations, the process 600 can also include identifying a first coefficient value based on the first resistance value, and identifying a second coefficient value based on the second resistance value, wherein the identity is based on an output value provided by a mathematical formula comprising the first coefficient value and the second coefficient value. For example, the resistor 1 14 can be determined to be "M" ohms, and the resistor 1 16 can be determined to be "N" ohms. The resistance values "M" and "N" can be applied to an equation such as "F = M ² +N" to determine a flow offset "F" for an FMU identified by the personality module 1 10.

[0096] In some implementations, a first component can provide the first resistor and the second resistor, a second component can provide the selector signal to the first component and measures the first resistance and the second resistance, and the second component can determine an identity of the first component based on the first resistance value and the second resistance value. For example, in the example system 100 the personality module 1 10 includes the resistors 1 14 and 1 16, and the control module 150 provides the selector signal at the port 160c and reads the resistances developed across the ports 160a and 160b to determine the identity of an FMU, an LRU, or other component associated with the personality module 1 10.

[0097] In some implementations the second component can be located remotely from the first component. For example, the control module 150 can be located remotely away from a harsh engine environment, and the personality module 1 10 can be located in, on, or near an engine component that is within an engine environment.

[0098] In some implementations, at least one of the first resistor and the second resistor can be a programmable resistor, and the process 600 can also include programming the programmable resistor to provide a selected one of the first resistance and the second resistance. For example, an FMU can be measured to determine that it flows 10ppm higher than specified at a first test flow point, and flows 50ppm higher than specified at a second test flow point. In examples such as this, the resistor 314 can be accessed through the SPI 380 and set to a 10 ohm resistance (e.g., to represent the 10ppm deviation), and the resistor 316 can be accessed through the SPI 480 and set to a 50 ohm resistance (e.g., to represent the 50ppm deviation).

[0099] In some implementations, the process 600 can also include providing a third selector signal at the selector port, connecting, based on the third selector signal, both the first resistor and the second resistor between the first bus and the second bus, and measuring a third resistance between the first bus and the second bus to determine a third resistance value, wherein connecting, based on the first selector signal, at least one or both of the first resistor and the second resistor between the first bus and the second bus comprises connecting one of the first resistor and the second resistor between the first bus and the second bus. For example, in the example system 400, a signal can be provided at the port 460c to present the resistance of the resistor 414 at the voltage sensor 454, a signal can be provided at the port 460d to present the resistance of the resistor 416 at the voltage sensor 454, and signals can be provided at the ports 460c and 460d simultaneously to present the resistance of the resistors 414 and 416 in parallel at the voltage sensor 454.

[00100] In some implementations, the process 600 can include providing at least one of the first selector signal and the second selector signal as a driver signal to a line replaceable unit (LRU), and driving operation of the line replaceable unit based on the driver signal. For example, the shut-off solenoid 420 can be an LRU that can be driven by selected combinations of signals provided at the ports 460c and 460d.

[00101] Although a few implementations have been described in detail above, other modifications are possible. For example, the logic flows depicted in the figures do not require the particular order shown, or sequential order, to achieve desirable results. In addition, other steps may be provided, or steps may be eliminated, from the described flows, and other components may be added to, or removed from, the described systems. In another example, the resistors 1 14 and 1 16 could be implemented to characterize or identify components other than an FMU, such as an actuator, a remote valve, a line replaceable unit or any other appropriate component that can be identified or characterized, directly or indirectly, by two or more resistance values. Accordingly, other implementations are within the scope of the following