Circuit for checking an electrical line connected to a digital input of an actuator

Abstract

System (100) with a terminal block (400) and an actuator (200) connected to the terminal block (400) via an electrical line (300), wherein the terminal block (400) has a circuit (420) with a digital output (430) to which the electrical line (300) connected to the actuator (200) is connected; the digital output (430) has a high level (600) in a first voltage range (700), a low level (500) in a second voltage range (710), and a third voltage range (720) formed between the first voltage range (700) and the second voltage range (710); and the actuator (200) has an activation voltage range (730), wherein the actuator (200) is activated by applying a voltage in the activation voltage range (730), characterized by the fact that the circuit (420) is set up: to output a test voltage (800), wherein the test voltage (800) differs from the activation voltage range (730) by a voltage difference (760).

Description

AREA

[0001] The present invention relates to the testing of an electrical line connected to a digital input of an actuator. BACKGROUND

[0002] Line faults, such as a line break or short circuit in an electrical line connected to a digital input of an actuator, are often only detected when the actuator cannot be activated by applying a corresponding voltage level to the electrical line. However, activating the actuator for diagnostic purposes before the need arises may be undesirable or impossible (especially during an ongoing process), for example, if the actuator intervenes directly in the process, i.e., not via a switchable intermediate element.

[0003] A connection terminal with an integrated current sensor is known from DE 43 12 760 A1. SUMMARY

[0004] In this regard, the present invention enriches the prior art by a system according to the invention, a terminal block according to the invention and a method according to the invention for checking an electrical line connected to a digital input of the actuator, which allow a check of the electrical line, for example with regard to short circuits and line breaks, during an ongoing process and in particular during an ongoing process in which the actuator intervenes directly upon activation.

[0005] The system according to the invention comprises a terminal block and an actuator connected to the terminal block via an electrical line, wherein the terminal block has a circuit with a digital output to which the electrical line connected to the actuator is connected, the digital output has a high level in a first voltage range, a low level in a second voltage range and a third voltage range formed between the first voltage range and the second voltage range, and the actuator has an activation voltage range, wherein the actuator is activated by applying a voltage in the activation voltage range and the circuit is configured to output a test voltage and / or a test current, wherein the test voltage differs from the activation voltage range by a voltage difference.

[0006] In this context, the term "actuator," as used in the description and claims, is to be understood in particular as a device that is configured to perform mechanical work when activated by supplying electrical energy. Furthermore, the term "digital output," as used in the description and claims, is to be understood in particular as an output configured to output discrete voltage levels relative to a reference potential. For example, a first voltage level (high level) can be 5 volts and a second voltage level (low level) can be 0 volts. Furthermore, the term "connected," as used in the description and claims, is to be understood as the presence of a continuous signal path, e.g., a continuous electrical line (which can be interrupted by a switch if necessary) between the connected components.

[0007] Furthermore, the term "voltage range" as used in the description and claims refers in particular to voltage ranges relative to the reference potential. For example, the first voltage range may comprise a voltage range from 2.4 volts to 5 volts with respect to transistor-transistor logic, TTL, or a voltage range from 4.4 volts to 5 volts with respect to CMOS logic, and the second voltage range may comprise a voltage range from 0.0 volts to 0.4 volts with respect to TTL, or 0.0 volts to 0.5 volts with respect to CMOS logic. Furthermore, the third voltage range may comprise a voltage range from 0.4 volts to 2.4 volts with respect to TTL, or a voltage range from 0.5 volts to 4.4 volts with respect to CMOS logic.

[0008] Since the test voltage lies outside the activation voltage range of the actuator's digital input, the line can be tested by applying the test voltage or a test voltage pulse without (unintentionally) activating the actuator. For example, an impulse response from the actuator's digital input can be recorded and evaluated in the form of current and / or voltage characteristics.

[0009] Preferably, the circuit is further configured to determine a current flow through the digital output while the test voltage is applied to the digital output.

[0010] For example, a cable break would result in a lower current flow, or a short circuit would result in a higher current flow than in a fault-free situation. This allows faults in the electrical line to be detected, for example, by comparing them with a current flow reference value or a current flow reference curve. The current flow reference value or current flow reference curve can be recorded during a learning phase with a fault-free connection or generated as part of an averaging process from various statistically independent measurement series.

[0011] Preferably, the circuit is further configured to generate an error signal if the determined current flow is below a first threshold value or above a second threshold value.

[0012] For example, the first threshold value can be lower than the current flow reference value and the second threshold value higher than the current flow reference value. The intervals between the current flow reference value and the threshold values ​​can be derived, for example, from (expected or measured) fluctuations in the current flow reference value. The error signal can then indicate the error condition as an acoustic or optical signal or be transmitted as a data signal to a higher-level controller that monitors the system.

[0013] Preferably, the circuit is further configured to repeat the application of the test voltage after a certain time interval automatically or in response to a signal received by the circuit.

[0014] By checking regularly, errors in the line can be detected before a desired activation, and appropriate measures such as stopping the process or adapting the process to an expected failure of the actuator can be initiated at an early stage.

[0015] The terminal block according to the invention for connecting an actuator comprises a circuit with a digital output for connecting an electrical line connected to the actuator, wherein the digital output has a high level in a first voltage range, a low level in a second voltage range and a third voltage range formed between the first voltage range and the second voltage range, wherein the circuit is configured to output a test voltage and / or a test current in the first voltage range or in the second voltage range, wherein the test voltage differs from the high level and the low level by a voltage difference.

[0016] The term "terminal block," as used in the description and claims, refers in particular to a terminal block arranged in an insulating housing, wherein the insulating housing is designed to be (detachably) connected to other insulating housings of the same type. Furthermore, the terminal block can be designed with a further electronic circuit for communication, in particular via a bus system, with terminal blocks of the same type, wherein the terminal blocks are detachably (electrically) connected to one another.

[0017] The method according to the invention comprises applying a voltage to the electrical line, wherein the value of the voltage is greater or smaller than values ​​of a voltage interval at which the actuator is activated, and monitoring a current flow through the electrical line driven by the applied voltage.

[0018] As already explained above, this allows the electrical line to be checked for faults without activating the actuator.

[0019] Preferably, the method further comprises generating an error signal when the monitored current flow is outside a certain current flow interval.

[0020] For example, the current flow interval can be determined in a learning phase or during (fault-free) operation of the actuator on the basis of a measured current flow and given safety intervals or as part of an averaging based on various statistically independent measurements.

[0021] Preferably, the method further comprises activating and subsequently deactivating the actuator, wherein the activating and deactivating of the actuator precedes the application of the voltage and the monitoring of the current flow.

[0022] This can, for example, reduce the risk that existing errors during the training phase will complicate or prevent subsequent testing.

[0023] Preferably, the method further comprises repeating the checking of the electrical line after a time interval by reapplying the voltage and remonitoring a current flow through the electrical line.

[0024] This means that, for example, line faults occurring during a running process can be detected before the actuator is activated and appropriate measures can be initiated, such as stopping the process or adapting the process to the expected failure of the actuator.

[0025] Preferably, the application of voltage and the monitoring of current flow are carried out automatically or in response to a specific signal by a circuit integrated in a terminal block. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The invention is explained below in the detailed description using exemplary embodiments, with reference to drawings in which: Fig. 1 a block diagram of a system with an actuator connected to a circuit integrated in a terminal block; Fig. 2 an exemplary signal curve for activating the actuator and checking the electrical line; Fig. 3 an example impulse response when checking the electrical line and a fault signal based on it; and Fig. 4 shows a flowchart of a procedure for checking the electrical line.

[0027] In the drawings, identical or analogous elements are identified by identical reference symbols. DETAILED DESCRIPTION

[0028] Fig. 1 shows a block diagram of a system 100. The system 100 comprises an actuator 200, wherein an input 210 of the actuator 200 is connected to a terminal block 400 via an electrical line 300. The terminal block 400 has an input 410 and an electronic circuit 420 connected to the input 410, which transmits discrete-value and discrete-time signals to the actuator 200 via a digital output 430. The input 410 of the terminal block 400 can be either an analog or a digital input 410.

[0029] The electronic circuit 420 has two operating states, between which the electronic circuit 420 switches during operation, either independently or upon receipt of a signal. In the first operating state, which corresponds to the normal case, i.e., active during process-related use of the actuator, the signals at the analog input 410 are output at the output 430 (e.g., looped through), or the signals at the digital input 410 are replicated or inverted at the output 430. This means that, for example, a high level at the input 410 causes a high level or a low level to be output at the output 430. If, for example, 5 volts or 0 volts are present at the input 410, 5 volts or 0 volts are also output at the output 430.

[0030] In the second operating state, the line 300 is tested for errors. As will be explained in more detail below with reference to Fig. 2, the electronic circuit 420 generates a test voltage at output 430 that differs from the voltage applied at input 410 and the low or high levels output during process-related use of the actuator 200. The conditions under which the electronic circuit 420 switches between the operating states can be fixed or adjustable by the design of the electronic circuit 420.

[0031] For example, electronic circuit 420 can be configured to switch to the second operating state and output test voltages according to a fixed or adjustable time pattern. Furthermore, it can be fixed or adjustable whether the output of test voltages is suppressed if the signals at input 410 are designed to cause a high level at output 430, or if the signals at input 410 are designed to cause a low level at output 430.

[0032] For example, if the output of the high level is suitable for activating the actuator 200 (i.e., if the high level is within an activation voltage range of the actuator 200), the electronic circuit 420 can be configured or set to disallow the generation of the test voltage if a high level is to be or is being output at the output 430. This can ensure that testing the line 300 does not disrupt or prevent the process-compliant use of the actuator 200 if it could be or is activated by outputting a high level.

[0033] Furthermore, if the output of the low level is suitable for activating the actuator 200 (i.e., if the low level is within an activation voltage range of the actuator 200), the electronic circuit 420 can be configured or set to disallow the generation of the test voltage if a low level is to be or is being output at the output 430. This can ensure that testing the line 300 does not disrupt or prevent the process-compliant use of the actuator 200 if it could be or is activated by outputting a low level.

[0034] In particular, the electronic circuit 420 can be connected to a mechanical switch (not shown) by means of which it is possible to switch between said settings, i.e., not allowing a test voltage while outputting a high level or not allowing a test voltage while outputting a low level. Furthermore, the electronic circuit 420 can have a signal input (not shown) via which a switching signal can be received, by means of which it is possible to switch between said settings, i.e., not allowing a test voltage while outputting a high level or not allowing a test voltage while outputting a low level.

[0035] Fig. 2 shows an example voltage curve U E at entrance 410 (in Fig. 2 above) and a voltage curve U partly derived from it A at exit 430 (in Fig. 2 below). The signal curve is directed to the case where the output of the high level is suitable to activate the actuator 200. As in Fig. 2, a low level 500 is initially present at input 410. Since electronic circuit 420 is in the first operating state, electronic circuit 420 outputs a low level 500 at output 430 and, following the signal waveform at input 410, switches to outputting a high level 600 at time t1, thereby activating actuator 200.

[0036] In this context, it should be noted that the output high level 600 (by the actuator 200) is detected as such by virtue of its being within a defined first voltage range 700. In this respect, the output high level, which is at the upper end of the first voltage range 700 (e.g., at 5 volts), is exemplary in nature, since the circuit 420 could also output lower high levels 600, which would also activate the actuator 200.

[0037] As in Fig. 2, at time t2, the electronic circuit 420 switches, again following the signal curve at input 410, to output the low level 500, thereby deactivating the actuator 200. In this context, it should also be noted that the output low level 500 (by the actuator 200) is detected as such because it lies within a defined second (lower) voltage range 710. In this respect, the output low level 500, which lies at the lower end of the second voltage range 710 (e.g., at 0 volts), is exemplary, since the circuit 420 could also output higher low levels 500, which would also deactivate the actuator 200.

[0038] As shown, a third voltage range 720 lies between the first voltage range 700 and the second voltage range 710. The "permanent" output of a voltage in the third voltage range 720 is not provided in the first operating state. Rather, the occurrence of voltages in the third voltage range 720 is linked to a voltage transition between the first voltage range 700 and the second voltage range 720, while transitions between the first voltage range 700 and the third voltage range 720 with an immediately subsequent return to the first voltage range 700 are not provided.

[0039] Similarly, transitions from the second voltage range 710 to the third voltage range 720 with an immediate return to the second voltage range 710 are also not provided. Furthermore, it should be noted that this also applies to voltages at the input 410, whereby the provided voltage range at the input 410 can also be divided into three voltage ranges 730, 740, 750, which correspond to the voltage ranges at the output 430, but include a smaller third voltage range 750 (in favor of the first and second voltage ranges 730, 740) to absorb transmission-induced corruption of an output voltage.

[0040] At time t3, the electronic circuit 420 changes in response to a test signal U Tinto the second operating state. In the second operating state, a test voltage 800 is briefly applied to output 430. This test voltage differs from the low level 500 output during the first operating state by a differential voltage, thereby generating a voltage pulse, and simultaneously differs by a voltage difference 760 from the input-side activation voltage range of actuator 200, which corresponds, for example, to the first voltage range 730. The current flow I generated by the voltage pulse mess through the output 430 is measured by the electronic circuit 420 and compared with a reference value I ref which was determined, for example, on the basis of a previous application of a test voltage of 800.

[0041] If the measured current flow I mess by more than a predetermined current difference I diff from the reference value I ref off, as in Fig. 3, concluded that there is a line fault and an error signal U F output by the electronic circuit 420. If the measured current flow I mess by no more than the predetermined current difference I diff from the reference value I ref the electronic circuit 420 returns to the first operating state at t4. Furthermore, as shown in Fig. 2, the application of the test voltage 800 can be repeated after a predetermined interval t5-t3.

[0042] Fig.4 shows a flowchart of a procedure for testing the electrical line 300. The process begins at 900 with the step of applying a voltage to the electrical line 300 that is outside the voltage interval 730 at which the actuator 200 is activated. The applied voltage is, for example, as described above, a test voltage 800 that differs from the high and low levels 500, 600 applied during the process-related use of the actuator 200. At step 910, the process continues by monitoring the current flow through the line 300, based on which line faults can be detected and indicated. LIST OF REFERENCE SYMBOLS 100 systems 200 Actuator 210 Entrance 300 line 400 terminal block 410 Entrance 420 circuit 430 Exit 500 Low Level 600 high level 700 voltage range 710 voltage range 720 voltage range 730 voltage range 740 voltage range 750 voltage range 760 voltage difference 800 (test) voltage 900 process steps 910 process step

Claims

[1] System (100) with a terminal block (400) and an actuator (200) connected to the terminal block (400) via an electrical line (300), wherein the terminal block (400) has a circuit (420) with a digital output (430) to which the electrical line (300) connected to the actuator (200) is connected; the digital output (430) has a high level (600) in a first voltage range (700), a low level (500) in a second voltage range (710) and a third voltage range (720) formed between the first voltage range (700) and the second voltage range (710); and the actuator (200) has an activation voltage range (730), wherein the actuator (200) is activated by applying a voltage in the activation voltage range (730), characterized by , that the circuit (420) is set up: to output a test voltage (800), wherein the test voltage (800) differs from the activation voltage range (730) by a voltage difference (760). [2] The system (100) of claim 1, wherein the circuit (420) is further configured to detect a current flow (I mess ) through the digital output (430) while the test voltage (800) is applied to the digital output (430). [3] The system (100) of claim 2, wherein the circuit (420) is further configured to generate an error signal (U F ) when the specific current flow (I mess ) below a first threshold value (I min ) or above a second threshold (I max ) lies. [4] System (100) according to one of claims 1 to 3, wherein the circuit (420) is further configured to initiate the application of the test voltage (800) after a certain time interval (t5-t3) automatically or in response to a signal (U Test ) to repeat. [5] Terminal block (400), comprising: a circuit (420) with a digital output (430) for connecting an electrical line (300) connected to an actuator (200); wherein the digital output (430) has a high level (600) in a first voltage range (700), a low level (500) in a second voltage range (710) and a third voltage range (730) formed between the first voltage range (700) and the second voltage range (710); characterized by , that the circuit (420) is set up: to output a test voltage (800) in the first voltage range (700) or in the second voltage range (710), wherein the test voltage (800) differs from the high level (600) and the low level (500) by a voltage difference (760). [6] Terminal block (400) according to claim 5, wherein the circuit (420) is further configured to detect a current flow (I mess ) through the digital output (430) while the test voltage (800) is applied to the digital output (430). [7] Method for checking an electrical line (300) connected to a digital input (210) of an actuator (200), comprising: Applying a voltage (800) to the electrical line (300), wherein the value of the voltage (800) is greater or less than values of a voltage interval (730) at which the actuator (200) is activated; and Monitoring a current flow (I) driven by the applied voltage (800) mess) through the electrical line (300). [8] The method of claim 7, further comprising: Generating an error signal (U F ) when the monitored current flow (I mess ) outside a certain current flow interval (I min ;I max ) lies. [9] The method of claim 7 or 8, further comprising: Activating and subsequently deactivating the actuator (200), wherein the activation and deactivation of the actuator (200) corresponds to the application of the voltage (800) and the monitoring of the current flow (I mess ) precedes. [10] A method according to any one of claims 7 to 9, further comprising: Repeating the checking of the electrical line (300) after a time interval (t5-t3) by reapplying the voltage (800) and again monitoring a current flow (I mess ) through the electrical line (300). [11] Method according to one of claims 7 to 10, wherein the application of the voltage (800) and the monitoring of the current flow (I mess ) automatically or in response to a specific signal (U Test ) is carried out by a circuit (420) integrated in a terminal block (400).

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