DE19847841A1 - Arrangement for identifying, functionally testing sensors, especially optoelectronic sensors, compares test sensor output signals, and different sensor types are connected in different combinations - Google Patents

Abstract

The arrangement has a test monitoring device (6) with at least two test outputs (S1,S2) at which periodic test signals are output and an equal number of test inputs (S1,S2) for receiving sensor output signals and a test unit that compares the test signals and sensor output signals. Different types of sensors (2,2') are connected to the test outputs and/or test inputs in different combinations.

Description

The invention relates to a device for identification and function monitoring of sensors, in particular of optoelectronic sensors.

Sensors are used in almost all areas of technology used, for example as optoelectronic sensors for monitoring hazardous areas, as light barriers, Light grids, light curtains etc. Such sensors must meet very high security standards set in national and / or international standards. In the European standard EN6149E-1 are for such sensors Security standards defined, whereby in this standard so-called A distinction is made between "type 2 sensors" and "type 4 sensors". According to this standard, type 2 sensors must be used for have a periodic test to get a dangerous one Cover failure (e.g. loss of sensor detection ver capacity, exceeding the specified response time etc.).  

The test signal must respond to the sensor part replicate. Type 2 sensors have an "electronic" Exit, d. H. they switch on when they respond Switching transistor through.

Type 4 sensors have facilities for self-testing the sensor and can at least some possible mistakes by this Uncover self-test. Type 4 sensors are available with electronics output and with relay output. You will see below referred to as type E or type R.

Monitoring devices for sensors must "know" what type of sensor is connected because the on the Evaluations based on sensor signals depending on the sensor type are designed differently. A way to Detection of the sensor type would consist in the off value switching so-called dip switches or "Juniper" (plug-in binder), the position of which depends on the respective sensor type corresponds. However, these switches would need to be replaced of the sensors can be set manually, which is a Can represent a source of error. This also means that Manufacturing costs increased.

The object of the invention is therefore to provide a device create that automatically different types of sensors unique identified.

This object is achieved by the specified in claim 1 Features resolved. Advantageous refinements and training The invention can be found in the subclaims.

The invention is based on the basic idea, the type identification by making the different types in different connection combinations to a test monitoring device and the test over monitoring device automatically the respective connection comm combination recognizes.  

It is assumed that the test device at least Has connections for two sensors and accordingly two Test outputs at which periodic test signals are output and two test inputs for these test signals. The Sensors are between these inputs and outputs. With a sensor type, the sensors are displayed "crosswise" closed, d. H. a first sensor lies between the first Test output and the second test input while the other Sensor between the second test output and the first Test input is.

The other sensor type is then connected uncrossed.

A third sensor type, preferably sensor type 4E, is produced internally a test pattern that only the test inputs of the test Monitoring device is supplied and that of the Test signals from the test monitoring device at the test outputs differs, so that this type of sensor also works properly is identifiable.

The test monitoring device generates during operation periodic test signals that are temporal on the two channels are offset so that they are free of overlap. The test signals preferably have an active level "low" and an inactive level "high", the signal level "high" is dominant if "high" and "low" levels meet.

In trouble-free operation, they are contained in the sensors electronic switch or relay switch tied so that the test signal through the switch from the respective test output to the assigned test input reached. Electronic switches delay the test signal by a predetermined time period of about 1 msec, which is called serves as another distinguishing criterion. With relay switches however, the test signal is passed on without delay. With light barriers, light grids or the like they are Sensors are used so that they operate correctly (Light reception) turn on your switch.  

As to differentiate between sensor types 2E and 4R the criterion of the connection combination is sufficient further criterion of the time delay as redundant Criterion. Leave with this redundancy carry out additional error checks, in particular Plausibility checks as well as connection errors, such as line breaks, Detect short circuit or cross circuit.

In order for individual interference pulses and thus faulty ideas not immediately switch off the monitored ones Creating a machine is to improve availability Availability provided that the test monitoring device has a counter that increments per test cycle or decremented. Will be the same in a test cycle. Sensor type as identified in the previous cycle, see above the counter reading is incremented by 1, in the other Case decremented by a 1. Becomes a "new" sensor type identified, it is only considered valid if if the counter reading has a predetermined value (e.g. 20) has reached.

Similarly, an error or a sensor change only considered valid when the meter reading is one has reached the predetermined minimum value.

In the following the invention in connection with the Drawing explained in more detail. It shows:

Figure 1a an embodiment of a circuit arrangement according to the invention with a first type of sensor (eg 2E.).

1b shows an embodiment of a circuit arrangement according to the invention with a second type of sensor (eg type 4R.).

Fig. 2a is a timing diagram of test signals of Fig. 1a;

Fig. 2b is a timing diagram of test signals of Fig. 1b;

Fig. 3 shows an embodiment of a circuit arrangement with a third type of sensor (eg 4E.);

Fig. 4 is a schematic diagram of the circuit arrangement according to the invention; and

Fig. 5 is a timing diagram of a counter variable.

Fig. 1a shows a circuit arrangement 1 for identification and function monitoring optoelectronic sensors, the z. B. in a light barrier, a light grid, a light curtain or the like can be used. Two sensors 2 and 2 'of type 2 are shown, each having a transistor switch 3 and 3 '. A control input 4 or 4 'of the transistor switch 3 or 3 ' is with a light-receiving element 5 or 5 ', such as. B. a photodiode of a light barrier connected. If the photodiode receives light, which is the case in normal operation when the light barrier is closed, the associated transistor switches 3 and 3 'are switched through, ie closed and open when the light barrier is interrupted.

The collector-emitter path of the transistor switches 3 or 3 'is connected to test outputs T1 or T2 and sensor inputs S1 or S2 of a test monitoring device 6 .

In the specific case of sensors of type 2, the transistor switches 3 and 3 'are connected "crosswise" to the test outputs and the sensor inputs, ie the transistor switch 3 is connected to the test output T1 with its input line 7 and to the output line 8 with the Sensor input S2 connected. In a corresponding manner, the transistor switch 3 'is connected with its input line 7 ' to the test output T2 and with its output line 8 'to the sensor input S1. The connection of the lines 7 , 7 ', 8 and 8 ' with the connections T1, T2, S1 and S2 can be done, for example, by means of screw terminals.

The connection "over cross" in Fig. 1a has the result that a test signal present at test output T1 reaches sensor input S2 via closed transistor switch 3 and vice versa, that a test signal present at test output T2 passes through sensor transistor switch 3 'to sensor input S1 arrives what can be used to identify the sensor type, as will be explained in more detail in connection with Fig. 2a.

In Fig. 1b, two sensors 10 and 10 'of another type are connected to the test monitoring device 6 . For example, there are type 4 sensors with relay switches 11 and 11 '. These sensors are connected to the test outputs T1 and T2 and the sensor inputs S1 and S2 "uncrossed", ie the input line 7 of the switch 11 is connected to the test output T1, and the output line 8 of the same switch 11 is connected to the sensor input S1. Correspondingly, line 7 'of switch 11 ' is connected to test output T2 and output line 8 'of switch 11 ' is connected to sensor input S2. A test signal at the test output T1 will therefore appear at the sensor input S1 when the switch 11 is closed and, accordingly, a test signal will appear at the test output T2 via the closed switch 11 'at the sensor input S2.

Otherwise, the type 4 sensors are usually designed with two channels, ie a "sensor" always contains the two switches 11 and 11 ', each with associated light-receiving elements 5 and 5 '. Another difference between the Type 4 and Type 2 sensors is that the Type 4 sensors can perform certain self-tests, which is indicated by self-test devices 12 and 12 '.

In the type 4 sensors, a distinction is even those with relay output, as shown in Fig. 1b and such like with electronic output, that is with transistor switches the type 2-sensors of Fig. 1a, which is explained in detail in connection with FIG. 3. Type 2 sensors, on the other hand, always have an electronic output.

Sensors with relay output work without delay, ie act like a looped through line if the relay switch is closed. The test signal is therefore passed through without delay. Sensors with an electronic output, on the other hand, have a certain delay, which is of the order of 1 ms, ie a test signal at input 7 or 7 'of the switch will appear at the output with a delay of the stated time. This is also used as a criterion for differentiating the sensor types.

FIGS. 2a and 2b show waveforms at the test outputs T1 and T2 and the sensor inputs S1 and S2 of the circuits of FIGS. 1a and 1b. Reference is first made to Fig. 2a. The test signal ST1, which has a quiescent level "high" and an active level "low" with the duration t1, is present at the test output T1 in FIG. 1a. This active signal is emitted periodically with a period tp at the test output T1. In a similar manner, a signal ST2 is also emitted at the test output T2, which is offset from the signal ST1 by a time period t3, the time period T3 being greater than the sum of the time period t1 plus the delay time t2, so that the active signals are not timed overlap.

The time period t1 is in a practical exemplary embodiment in the order of magnitude between 24 ms and 150 ms. In the case of the circuit of FIG. 1a with sensors connected “crosswise”, the test signal ST1 is shown by the delay time t2 of the transistor switch at sensor input S2. In contrast, the test signal ST2, which is offset in time by t3, appears at the signal input S1 as signal SS1 when the transistor switch 3 'is closed - again delayed by t2. In an evaluation circuit to be explained in more detail in connection with FIG. 4, it is checked whether the signal ST1 appears with a time delay or without delay at the signal input S1 or S2. The sensor type can then be identified on the basis of this check.

Fig. 2b shows the corresponding signals for the circuit of Fig. 1b. It can be seen that the signal ST1 appears as signal SS1 at sensor input S1 and that without delay. The same applies to the signal ST2 at the test output T2 and the signal SS2 at the sensor input S2.

It should also be pointed out that FIGS. 2a and 2b are not to scale, in particular that the delay time t2 is smaller in relation to the pulse time t1. It should also be emphasized that the time period t3 is greater than the sum of t1 + t2, so that the active pulses do not overlap.

From the above it can be seen that to distinguish two Sensor types only one criterion is sufficient, for example the "crosswise" connection of the different sensor types or the evaluation of the time delay t2 between the test signal and sensor input signal. Because of the possible here Evaluation of two criteria, namely the "crossed" or "uncrossed" connection as well as the undelayed or delayed signal transmission, there is a Redundancy that can be used for further tests can.

This allows various sensor errors to be determined. For example, a line interruption is recognized by the fact that the test signal does not arrive at any of the sensor inputs. A short circuit between the lines 7 and 7 'and / or 8 and 8 ' is recognized by the fact that a high level is constantly present at the sensor inputs S1 and S2, since the circuit is designed so that the high and low levels coincide at the same time at a connection the high level is dominant. The test signal with an active low level would then not appear at any of the sensor inputs. A short-circuited transistor switch 3 or 3 'is recognized by the fact that the test signal appears at the "correct" sensor input but does not appear without delay.

Alternatively to the embodiments of FIGS. 1a and 1b, the two types of sensors 2 sensors can also be connected in different, so for example, the type of non-crossing, and the Type 4 sensors crossed to the test monitor 6 can be connected. The evaluation criteria then change accordingly.

FIG. 3 shows an exemplary embodiment with type 4 sensors which, in contrast to FIG. 1b, have electronic outputs, that is to say transistor switches 3 and 3 '. These sensors are called Type 4E sensors. In contrast to the type 4 sensors with relay output, the type 4E sensors do not require any external test signals. Rather, they automatically generate internal test signals at periodic intervals that have a different pattern than the external test signals, which can also be used to clearly identify these sensors.

Fig. 4 shows a schematic diagram of the test monitoring device 6 with the test outputs T1 and T2 and the inputs S1 and S2. About screw terminals 13 or other connection medium, such as. B. connectors, the lines 7 , 7 ', 8 and 8 ' according to FIGS. 1a, 1b or 3 are closed. A pulse generator 14 generates the pulses ST1 and ST2 in accordance with FIGS . 2a and 2b and periodically outputs them to the test outputs T1 and T2. At the same time, these signals are fed to a test unit 15 , to which the signals SS1 and SS2 are also fed from the connections S1 and S2. In this test unit 15 , the signals ST1 and ST2 are compared by the signal generator 14 with the signals arriving at the connections S1 and S2. It is checked whether

S1 = T1
S1 = T2
S1 = T1 + t
S1 = T2 + t
S2 = T2
S2 = T1
S2 = T2 + t
S2 = T1 + t.

In addition, it is also checked there whether the pattern generated by sensor type 4 E ( FIG. 3) is present at inputs S1 and S2. A signal, for example as a numerical value, is thus present at the outputs of the test unit 15 for the two channels S1 and S2, which identifies the individual sensor types. These values are fed to a memory 16 and to a module 17 for plausibility and error checking.

Due to interference pulses, it is conceivable that an incorrect sensor type is identified within a test period tp. In order to avoid such incorrect identifications, the test monitoring device has an integrating behavior in such a way that a different sensor type than previously identified is only properly identified if this occurs several times, for example twenty times. For this purpose, a counter 18 is provided which, depending on whether the previously identified sensor type has been identified again, counts upwards or downwards when a previously unconnected sensor type is identified. In the stationary case, in which the same sensor type is constantly identified, the counter is at its predetermined upper limit of z. B. 20. If a "new" sensor type is identified for the first time, the counter only counts down by 1, ie to the value 19, which otherwise has no effect. Only when the counter has counted down to a predetermined lower limit value is a signal sent to the memory 16 , which then takes over the new sensor types. The memory 16 therefore also contains a comparator which compares the values of the stored sensor types and the newly determined sensor types and, depending on this comparison, gives the counter 18 a counting pulse for counting up or down. Similarly, the unit 17 for the plausibility and error check sends up or down counting pulses to the counter, which only delivers an error signal to an evaluation and monitoring unit 19 when the corresponding error has occurred several times. The unit 17 then optionally reports the type of the determined error to the evaluation unit 19 .

Fig. 5 shows a possible time variation of the count contents of the counter 18. In the initialization phase of the test monitoring device it can be provided that the counter starts from a starting value Z ₈ , which lies between the maximum and the minimum counting content, and that the values of the sensor types determined during the last operation are stored in the memory 16 .

But it is also possible to set the counter in the initialization phase at the lower limit, e.g. B. start at 0 and write the values in the first test period in the memory 16 , but only then pass the corresponding values on to the evaluation unit 19 when the counter has reached the value Z _max (for example 20) . It can also be provided that an enable signal for a machine to be monitored is only generated when a predetermined number of identification periods has passed after the initialization phase and the counting content of the counter 18 has exceeded a predetermined value.

If, on the other hand, errors occur, the counting content increases decremented every period, with errors tolerated as long or as "interference" as long as the Counting content lies between the minimum and the maximum value. For example, if the count content is 10 and enter in ten consecutive identification periods, each z. B. last 200 ms, errors on, then Z is after 2 s "integrated" to 0, which is the criterion for switching off the machine to be monitored is viewed.

Claims (10)

1.Device for identifying and checking the function of various sensor types, in particular sensors which can be used in an optoelectronic device, with a test monitoring device ( 6 ) which has at least two test outputs (T1, T2) at which test signals (ST1, ST2) are output periodically and which has an equal number of test inputs (S1, S2) for receiving sensor output signals (SS1, SS2) and a test unit ( 15 ), which compares the test signals (ST1, ST2) and the sensor output signals (SS1, SS2), with different sensor types in Different connection combinations are connected to the test outputs (T1, T2) and / or test inputs (S1, S2). 2. Device according to claim 1, characterized in that in a first sensor type, a sensor ( 11 ) between the first test output (T1) and the first test input (S1) and the second sensor ( 11 ') between the second test output (T2) and is connected to the second test input (S2), while in a second sensor type a first sensor ( 3 ) between the first test output (T1) and the second test input (S2) and the second sensor between the second test output (T2) and the first test input ( S1) is connected. 3. Apparatus according to claim 1, characterized in that in a third sensor type, which contains a self-test device ( 12 , 12 '), only the outputs ( 8 , 8 ') of the sensors ( 3 , 3 ') to the test inputs (S1 , S2) are connected. 4. The device according to claim 1 or 2, characterized draws,  that the test signals (ST1, ST2) overlap-free are offset from one another in time. 5. Device according to one of claims 1, 2 or 4, characterized, that the test signals are low when active Level and have a high level when inactive. 6. The device according to claim 2, 4 or 5, characterized in that the one sensor type the test signals without delay and the other sensor type switches through the test signals with a time delay (t ₃ ). 7. The device according to claim 4 and 6, characterized in that the period (t _p ) of the test signals is greater than the sum of the time offset of the test signals and the delay time (t ₃ ) of the one sensor type. 8. Device according to one of claims 1 to 7, characterized in that the test monitoring device ( 6 ) has a counter ( 18 ) which is incremented or decremented after each test period depending on whether the previous or another sensor type during this test period was identified. 9. Device according to one of claims 1 to 8, characterized in that, depending on a comparison of the test signals sent out (ST1, ST2) and the received sensor signals (SS1, SS2), a plausibility and error checking unit ( 17 ) generates an error signal. 10. Device according to one of claims 1 to 9, characterized featured, that assigned test outputs (T1, T2) and test inputs  (S1, S2), between which there is no sensor, with a Wire bridge are connected.