SIGNALS

The present invention relates to an arrangement for the dis¬ tribution and/or extraction of signals, as stated in the in¬ troductory part of the following claims.

The field of application will mainly comprise interrogation and conversion of a large amount of sensor informationin time division multiplex _ on a common line as well as transmission of information to points on the same line. It is possible by suitable combinations in the form of connection and tapping of the line signal paths to build a multidimensional struct¬ ure of self generating combinatorial circuits.

In the art various kinds of time multiplex are known. German Specification 1 240 446 discloses such a device.comprising several seguencially connected mono-stable multivibrators, the first one triggering the next etc. Resistive or capaci- tive sensors are among the components controlling the time during which the multivibrator is in a working state after a received trigger signal. After the multivibration has fallen back into a resting position the subsequent multivibrator is triggered, etc.

The previously known systems involving use of multivibrators have the disadvantage that they are a load on the common signal and power supply line, every second transistor in the multivibrators always being conductive as well as the associated components of the circuit. With an* increasing load on the line there will, thus, follow a reduction of the possibility of detection and transmission in the form of short current pulses generated on a common line. A consider¬ able weakness is that erroneous triggering is easily releas¬ ed by transients on the line or through the sensors, which may give rise to completely uncontrolled firing of the sepa¬ rate multivibrators. A considerable disadvantage is, thus, that the sequence and the number of monostable multivibrators are not forcibly actuated from a point on the chain, prevent-

OMPI

ing this form from being an integral part of a selfgenerat- ing combinatorial circuit.

It is, thus, an object of the present invention to overcome said disadvantages, and the characterizing features of the invention will appear from the following claims as well as from the following description with reference to the drawing.

Fig. 1 is a schematic illustration of the arrangement accord¬ ing to the invention.

Fig. 2 is a block diagram of the arrangement according to fig. 1.

Fig. 3a shows examples of switching elements, and Figs. 3b, and 3c show combinations of switching elements as well as delay circuits.

Fig. 4 is a block diagram of a non limiting embodiment of a delay - line provided with several branches and illustrates combinations of the typical inputs and outputs.

Fig. 5 illustrates an embodiment of delay lines used for measuring temperature gradients or mechanical tensions in a construction member, e.g. a beam or a plate.

Fig. 6 illustrates a delay line - according to the invent¬ ion used as a level indicator.

Fig. ^' 7 illustrates a similar arrangement for recording tem¬ perature/temperature gradients in a medium.

Fig. 8 is a diagram showing the current through the swit¬ ching element as a function of the control signal on said switching element.

Fig. 9 is a typical illustration of the pulse sequence in connection with the various elements of a delay n _n e

O PI

Fig. 10 shows a delay line substantially as shown in fig . 1 , but with passive elements illustrated .

Fig. 11 shows a variant of a delay ;J.ine.haying__feed- back.

Figs. 12a-d illustrate some current sensing arrangements.

In Fig. 1 switching elements 1 and delay circuits 2 are shown in a cascade connection. The common circuit is formed by connections 8 and 8' and a current source 10. In principle the cascade connections form a delay line with the charac¬ teristic inputs and outputs of different kind. As shown in Fig. 1, these are mainly to be considered as static or dy¬ namic. A control input 3 is provided for activation of the delay line at a change from a voltage level V to V,, or vice versa. In this manner it is determined which of the switches are open in a determined' sequence and which of the switches are to close. During a short transition phase, when one switch S-, or S ₂ resp. closes before the other opens, the circuit 8, 8' will consequently be closed.

After a delay that is substantially determined by delay circuit 2, the same procedure is repeated and, thus, only one switching element at a tine will be connected to the common circuit. Also, the number of switching elements in the sequence to be activated is controlled by the aid of the activating input 3.

Delay element 2 is provided with a direct input 6 affecting its time constant.

On an output 5 a dynamic output transmission is provided in short current pulse form from a sensing element 9 connected to the common circuit 8,as switching elements 1 close the circuit for short periods. The interval Δt between pulses is directly proportional to the time constant in the inter¬ mediate delay circuit 2.

f OMPI

Output 4 represents the output on the last switching ele¬ ment in the delay line. Output 5 can record the current pul¬ ses from all switching elements connected to the common cir¬ cuit by the aid of sensor element 9. This may also occur at outputs 5.1 and 5.2 in the form of partial recording by sen¬ sor elements 9.1 and 9.2, which for instance may be located as shown in Fig. 1.

The time T consumed to effect a change of state in all switching elements on the entire line equals the sum of the separate time delays Δt.

Each of the shown outputs 7 represents a static output from each of the switching elements 1. The level will change bet¬ ween V and V-, at every single change of state. An output 7 can be in phase or in antiphase with the input of the swit¬ ching element, depending on the construction of said swit¬ ching element.

In Fig. 2 the arrangement of Fig. 1 is shown in block form, where only inputs and outputs are indicated.

Fig. 3a shows some simple alternative switching elements, -1 being a symbol of the switching element with its connection with the common lines and input as well as output of the switching element. 1.1 illustrates a simple form of a swit¬ ching element consisting of two inverting sequencially connected elements to achieve non-inverting as well as. an improved switch characteristic. 1.3 illustrates a mainly mechanical switching element having the same main features as stated above.

In Fig. 3b the switching elements consist _of semiconductors,, e.g. complementary MOS transistors, the control of switches being effected by a change of state on the switching element input. When e.g. switch S, is a P-channel and S ₂ a N-channel transistor, the first mentioned is open and the second one closed, depending on the common control input 3 of the switch being closer to V than V, , or vice versa. Only in

O PI

the transfer phase as shown in Figs. 8 and 9 both are con¬ ductive. ^*

Fig. 3c shows an arrangement comprising mechanical switches, input 3 controlling the change of state of switches S, and S-. The delay element consists mainly of a resistance R and a capacity C, which may be variable and may consist of various sensor elements to affect the time delay Δt. Input 6 permits the application of signals from outside to change the time constant from other circuit elements, sensors, feed backs from other delay lines, etc.

In Fig. 4 a block diagram illustrates a non-limiting embodi¬ ment of an arrangement of delay lines connected by their respective inputs for activating said delay lines 3.1 - 3.4 and 6.1 - 6.4 to control the delay circuits e.g. in the form of sensor elements. Outputs 5.1 - 5.4 represent the time intervals of the separate lines in form of current pulses.

Outputs 7.1 and 7.2 show branch lines that activate further lines after a certain number of time intervals. It is, fur¬ thermore, shown how the output on a branch line IV near out¬ put 7.4 affects the propagation time on line I. The degree of influence is affected by the time delay between changes of state on input 3.4 and output 7.4. Output 7. affects the delay element via input 6.1 on line I. A signal S represents an instant at which e.g. outputs 7.1 - 7.4 have a certain state that is detected by a gate, indicated at G.

In the Figure a summing circuit A is shown having inputs 5.1 - 5.4, which may be connected to the outputs of the lines resp. The sum of time intervals as well as the rrutual dis¬ tribution in time is represented by output B of the summing circuit. To make it easier to distinguish between the sepa¬ rate line signals in output B of the summing circuit A, the separate inputs 5.1 - 5.4. ay have different levels and/or polarities.

OMPI WIFO

Fig. 5 shows a two-dimensional structure of said delay lines, where main line I upon an input A activates branch lines II- V from their outputs 7.1 - 7.4 resp. On surface F sensors are provided and influence the delay Δt on the delay circuits of branch delay lines II-V. Upon summation in a summing circuit S that is connected to outputs 5.0 - 5.4 by lines I-V a puls pattern B will be characteristic for the measur¬ ing parameters of the separate sensors. It is also possible to achieve further distinction between lines by difference of amplitudes _*

Fig. 6 shows an embodiment of a one-dimensional structure representing a level measuring arrangement with capacitive sensors. The level or levels, if there is a question of layer formations of several media with differing dielectric constant, will be recordable only by change of capacity bet¬ ween a ground reference JR and the sensor elements C, , C~, and C^. RT, R , and R^ are passive resistance elements, included as part of the delay element together with C-., C ₂ , and C- resp., and either being in direct contact with the measured medium or insulated from said medium by an insulat¬ ing material 4, depending on the nature of the measured" medium 15.

Switching elements B-, - B _* are connected with a common cir¬ cuit 8 via current sensor 9 and current source 10. The sig¬ nal processing electronics 11 start interrogation at a change of state on line 3 input and receive a signal on output 4 from the last switching element B . when all elements C-,, C ₂ , and C^ have been interrogated. ^" Current puls-es from current sensors 9, as shown in diagram 13 comprising time intervals Δt,,Δt ₂ , and Δt^, are processed by electronics 11 and are presented in a suitable form in 12, i.e. an optional display or diagram listing

Fig. 7 shows a delay line I that _{scans a} number of states of a medium, e.g. a mass of soil, in order to record differences of e.g. moisture, temperature, pH-values or combinations of

^{f OMPI}

these parameters, suitable sensor elements 6-, - 6_ being lo¬ cated in said mass of soil and connected to the inputs of line I.

Fig. 8 illustrates the transition phase when input 3 of the switching element changes state, i.e. both switches are con¬ ductive and the current I through the switches reaches its maximum value. This occurs in area III as shown in the Figure.

In Fig. 9 the relationship between current pulses B on the common conductors and the voltage levels V. 1-4 on the control inputs of the switching element is shown by way of example. Here, an embodiment is considered comprising four switching elements with associated delay circuits. The swit¬ ching elements in the shown embodiment are non-inverting.

Fig. 10 illustrates various arrangements of the delay cir¬ cuit. 2.1 illustrates how capacitor C as a sensor element has been connected between input and output of the switching element.

-In _Fig. 11 a.del y line -is shown havin -feedback and-in the--

-shown-example.being.capable.of reactivating itself upon_a_ change of state on the output of the last control signal 7.4, and,,the available-control—sign l 7.1---7-4 occurring: _. in_a__ time sequence determined by e.g. the sensor via inputs 6.1 -

6.4. Gate G in the shown embodiment comprises an inverting "AND-gate" that controls the ...feedback function by the ^"~"~ . aid of the signal line a from signal processor p, which also processes the current pulses from line output 5. A typical puls diagram is also shown.

In Figs. 12a-d various sensing systems for the dynamic pulse train on the common conductor 8 in series with current supply 10 are shown. Fig. 12a illustrates the recording of current pulses as voltage drops via resistance R on output 5. Fig. 12b shows the recording of current pulses in the form of capacitive connection to circuit 8. Figs. 12c and 12d show

OMPI

various transformer connections 12 and 13 for recording the current pulses in the circuit.

The invention described above permits an almost infinite ^• 5 number of sensors to be connected to a common line without _loading__it_._ This means that in a state of ^" rest all sensors and possible delay lines are disconnected from the line^

When the line is activated, this is controlled from the end point forming the starting point. Consequently the line is 0 only loaded for a short time, and only by one element at a time, whereas the sensor or portions of it determine the time delay Δt of the next load, provided that the control signal from the input is not changed. In this manner the line impedance is kept approximately constant, i.e. it is 5 only affectable to a small degree or almost not affected by the number of sensors or elements involved in the line.

In contrast to known systems utilizing multivibrators the present invention represents a system its _spe-_ _ 0 cial construction and mode of operation is almost unaffected by temperature and voltage and is inaffectable by transient or _.. parasitic _, pulses. ^" This is Targely ^" due ^" jo the main circuit 8,8' is only loaded by active components, i.e. the passive components only determine the delay interval Δt. 5 The number of components is, thus, reduced to a minimum.

Another characteristic of the present invention is the fact that the line with sensors or pure delay networks or^ a com- ^~~ bination of such components may be used in a multi-dimension- 0 al structure of selfgenerating combinatorial circuits. The line may be considered as a coupling means with several different inputs to control said line as well as outputs to control other lines or systems as described below.

5 The arrangement, thus, in principle comprises a current source ^" _. ^" across ^" which one or a plurality of switching elements are connected in parallel. The switching elements again con¬ sist-of ^" two ^' switches ^' connected ^"' in series, ^' anα ^" _n ^_ a ^' sta€e ^" of ._rest one .is always open and .the other closed..

_ OMPI

This means that the circuit is always open. A delay circuit connects the separate switching elements, the output of the first element being connected to the input of the subsequent element, etc. When said first switching element is activated one of the switches, i.e. the open switch, will close some¬ what before the closed switch is opened (make before break) .

A current pulse of short duration is recorded on the main circuit when it is loaded by a "short circuit", the current being limited by the inherent resistance of the switch in series with the main current source.

After a delay determined by the delay circuit the same will occur with the next element, etc.

The delay circuit can consist of any delay circuit that con¬ sists solely or partly of a sensor or the like. It may be suitable to connect said switching element with said current source via a common line. In principle this constitutes a delay line.

The sequence of signal propagation to change'switch states' in the separate switching elements is determined by the de¬ lay circuits between switching elements.

The rate of signal propagation varies with the separate de¬ lay circuits. This means that the total delay is at any time determined by the sum of every single delay element in. the line.

The extent of signal propagation, i.e. the number of ele¬ ments to change their switch state, is determined by the control signal on the first switching element. If said switching element . returns to its original state before all elements have changed their state, those elements that have changed state will return to their original state. In this manner ^' the extent and direction of the delay line is controlled.

O PI

From the above description it will appear how it is possible to extract measurementdata from a comparatively large number measuring points in time division,multiplex. By recording the current pulses on different points on the line said pul¬ ses may be utilized as partial information in the form of a dynamic output for the line extent in time.

As a unit the line may be considered a coupling element with inputs and outputs. The inputs are essentially as stated above. The control signal initiates and determines the ex¬ tent of signal propagation. Inputs directly influencing the delay between the separate switching elements will be contri¬ butory as to the rate of propagation. As well as being sens¬ ing, capacitive, inductive, or resistive elements, or combi¬ nations thereof, said input signals may also be voltage or current levels.

The output signals occur in two main groups. Outputs of a more dynamic kind are tapped at different locations from the line or in one or several of the switching element branches from the main line. Outputs of a more static kind are repre¬ sented by the centers of the switching elements, which main¬ ly change between zero and the voltage on the main line. This also applies to the last element of the line, i.e. when the entire line has been swept and all switching elements have changed state.

With said inputs and outputs the signal information on the line.may be described as two-way, as it is possible to gather as well as pass on information.

The described invention in the first place offers great possi¬ bilities for scanning large number of measuring points con¬ verted to time division multiplex as well as for combinations of inputs and outputs from several lines in such a manner that they result in a multi dimensional structure of self generating combinatory circuits.

Possibilities of combining will also exist within one and

the same line, where some of the sensors in a specific geo¬ metric grouping will influence the scanning pattern of an¬ other groupj also the scanning sequence of sensors is such that the dynamic pulse pattern occurs in a characteristic time sequence, as shown in Figures 4, 6 and 7.

Among other possible applications the following are mention¬ ed: A continuous supervision of structures with suitable sensor elements located near construction details to be super- vised from a central position. This may concern dams, where it is of interest to record moisture gradients and settle¬ ment.

Another application is security supervision to point out alarm positions. The utilized sensor system may. record chang¬ es of pressure, temperature, acoustics, light, or simply a closed or open contact.

Depending on the field of application signal processing will always require signal processing electronics which process the signal information to the desired kind of display, de¬ tects alarm criteria ^' and controls operations. To carry out said tasks some kind of microprocessor will form the most universal solution.

The possibilities of application offered by said switching elements are best comparable with the sensory and motory signal paths of a living nerve system and its countless logical connections.

O PI IPO