DE202008012472U1 - Optoelectronic sensor - Google Patents

Abstract

Opto-electronic sensor, in particular light grids (2)
with at least one light transmitter (6) for emitting light pulses,
with at least one light receiver (4) for receiving the transmitted light pulses,
with a control and evaluation unit (AE) for controlling and evaluating at least the light receiver (4) and a monitoring unit (UE) for checking at least the function of the control and evaluation unit (AE),
wherein the control and evaluation unit (AE) is diversified to the monitoring unit (UE)
and the control and evaluation unit (AE) and the monitoring unit (UE) are connected to a switching unit (SE) for outputting a switching signal,
characterized in that
the monitoring unit has at least one output (8) which is connected to the control and evaluation unit (AE), for outputting at least two different test vectors (26, 28) to the control and evaluation unit (AE) and at least one input (10 ), which is connected to the control and evaluation unit (AE), for reading an output signal (UEin / AEout) of the control and evaluation unit (AE), ...

Description

The The invention relates to a device according to the preamble of the claim 1.

Safety-related optoelectronic sensors are subject to high demands with regard to required reliability in accordance with various nouns, such as, for example, the standard "Safety of Machinery - Non-contact Safety Devices (ESPE)", EN / IEC 61496 or the European standard "Functional safety of safety-related electrical, electronic, programmable electronic systems", EN 61508 , The optoelectronic sensors are subdivided into safety categories, which are included in the standard "Safety related parts of control systems" EN 954 or their successor form EN 13849 are fixed.

Around To meet these requirements sensors are multi-channel (redundant) with identical channels and elaborate tested. Standardized security levels are necessary because such Sensors as protective measures on dangerous machines, such as presses, stamping tools, robots, and the like. Ä. Used and thus life and health of operators of the Functionality of the sensors depends, so the sensors in the event of danger, a safety-related switching signal can give. The redundancy leads to high costs for the needed hardware while the Safety tests adversely increased a response time of the sensor.

From the DE 692 25 487 T2 there is known an active error checking mechanism which monitors an entire light curtain control system. The mechanism consists of a pair of microcontrollers consisting of a system microcontroller and a watchdog microcontroller. The function of the system microcontroller is to operate the light curtain and to check the function. One of the main controls performed is to introduce a test signal through the watchdog microcontroller to the optical transmitter of the light curtain to simulate a light interruption and then to verify that the entire light curtain including the system microcontroller is correctly responding, especially if there is a switching signal in the receiver is produced.

These However, the device has significant disadvantages. That's the way it is, for example not possible if the light beams are interrupted to carry out a test because the test signal is not transmitted can. Thus, the function of the light curtain can be only check completely with a free protective field.

Of the Invention is based on the object, an improved optoelectronic Sensor that can be easily tested, even if one or more optical links interrupted and / or the protective field injured between a light transmitter and a light receiver is.

The Task is according to the invention according to claim 1 an optoelectronic sensor solved, in particular a Light grid with at least one light emitter for emitting light pulses, and at least one light receiver for receiving the transmitted light pulses. Next are a control and evaluation unit at least the light receiver and a monitoring unit for evaluation to verify at least the function of the control and evaluation provided. The control and evaluation unit is diversified to the monitoring unit and the control and evaluation unit and the monitoring unit are equipped with a switching unit for outputting a safety-related Switching signal connected. The monitoring unit points at least one output connected to the control and evaluation unit is to output at least two different test vectors to the control and evaluation unit and at least one input, which is connected to the control and evaluation unit for reading an output signal of the control and evaluation, which of depends on the test vectors. In the monitoring unit Comparing means are provided to the output signal with at least compare two different expectation values and dependent from the result of the comparison, the switching unit to control eventually, if necessary, the dangerous movement the machine can shut down in case of malfunction of the sensor.

One Advantage of this embodiment of the invention is that checks all the electronic components involved in the evaluation of the received signals and also implemented software programs are tested. Dodge that Output signal decreases by more than a defined tolerance, so is during the evaluation of the control and evaluation unit a deviation occurred, for example, in a particular data processing path. thereupon the sensor function is switched off in a safety-related manner. By the input test vectors can thus be the whole safety-critical Evaluation of the evaluation be tested.

The test vectors are evaluated by the control and evaluation unit as the reception signals of the optical light receiver. The evaluation unit does not need or need to differentiate between the test vectors and the received signals. If an error occurs in the control and evaluation unit, which is safety-critical to the evaluation affects the received signals, so this error also has an immediate effect on the processing of the test vectors and can be detected directly by the monitoring unit. For this purpose, the test vectors are compared in the monitoring unit with the expected values. If the test vectors deviate from the expected values by a certain specified tolerance, then the switching unit is actuated in a safety-oriented manner and, if appropriate, a switching signal is output in order to stop a dangerous movement.

There the test vectors from the control and evaluation unit as well as the received signals are evaluated, is the control and evaluation constantly operated in the "sharp" evaluation mode and not, as was previously the case, at times in a special one Error test mode. Through the monitoring unit is the Control and evaluation unit thus during the current Evaluation process of the light receiver tested. this leads to that an evaluation time is shortened, since no separate time test phase has to be considered more. Much more The check will be in parallel to the ongoing operation the control and evaluation made. This improves the Response time of the optoelectronic sensor considerably.

With the different test vectors can both states "light path free "and" light path interrupted "simulated become. This makes it possible, even with a permanent Interruption of the light path the control and evaluation completely and easy to test. By the monitoring unit is then check whether the evaluation of the tax and evaluation unit for both test vectors properly works. This measure also causes an error accumulation avoided, which could result if for a no period of review would. A failure of the light curtain during a permissible material supply while of which all light rays might be covered, would be recognized as well.

The monitoring unit is much simpler than the control and evaluation unit itself, because the monitoring unit has only the task, the Output test vectors to perform a comparison with expected values and depending on the comparison to make a reaction, namely to influence the switching unit. The elaborate Control and evaluation is thus only by a very simple monitoring unit added. Thereby the optoelectronic sensor is very inexpensive to produce. Due to the simple structure of the monitoring unit, this can even redundant and / or diversified to ensure further, higher error safety and to increase a security level without the effort significantly increase for the optoelectronic sensor.

The In principle, test vectors can be found anywhere in the control and evaluation unit of the optoelectronic sensor are fed, so that interfaces, peripherals, analog-to-digital converters or amplifiers be tested. It is important that the test vectors with the same algorithm that works for the evaluation of the received signals in "normal" operation is used.

In Development of the invention, the at least two different Test vectors output alternately from cycle to cycle. One cycle corresponds to the one-time successive activation of the light emitter and light receiver of the light grid. Through the alternating Output, dynamic testing is achieved, the static errors better reveals. For example, an error would be in the form an infinite loop in generating the test vectors revealed because of the alternately tested test vectors are also alternating output signals for the monitoring unit generated.

The dynamic testing is that after each cycle the order the two different test vectors is changed, so that the control and evaluation, for example, after two Cycles can detect if a corresponding change took place. A Such evaluation is referred to as a double evaluation, since this An error message is issued only when in two cycles in a row the review was unsuccessful. So long an alternating sequence of the output signals is detected thus ensuring the proper function of the sensor.

Advantageously, the test vectors are formed by analog and / or digital signals. This makes it possible to provide both analog and digital signals for the control and evaluation and to comprehensively test the control and evaluation unit, which evaluates these signals. For example, it is provided that the test vectors are input as analog signals into the control and evaluation unit, but these are converted by an internal analog-to-digital converter in the control and evaluation unit and digital output signals are compared by the monitoring unit with digital expected values. As a result, the monitoring unit can be further simplified, since only digital input signals still have to be processed. Conversely, it is also provided that digital test vectors are output via a digital-to-analog converter in the control and evaluation unit in analog output signals, and compared with analog expectation values become. In a further embodiment, the test vectors are also mixed analog / digital signals, which are supplied, for example, via different inputs of the evaluation unit. Only analogue test vectors and analogue signal processing for comparison with analogue expected values are provided for very simple sensors, which do not require a digital control and evaluation unit or, after a digital evaluation, provide analogue output signals for an analog control of the switching unit. Purely digital test vectors come into consideration for image sensors in which digital image information is present and an output signal of the control and evaluation unit in turn provides only a digital switching signal for the switching unit. As a result, the monitoring unit is designed as a purely digital logic circuit.

Around to increase the range of optoelectronic sensors and to ensure eye safety is in such Sensors usually pulse the light of the light emitter sent out and received accordingly by the light receiver. The pulses have predetermined same or different, but defined intervals on to a high signal-to-noise ratio to ensure against external light. Advantageous the test vectors are exactly adapted to this pulse sequence. Thereby can be a signal path directly from the light receiver, for example a photocell or the light grid tested effectively become. The amplitude of the pulse train of the test vectors can thereby be different to the pulse train of the received signals.

In According to a further development of the invention, the first test vector has a first test vector Pulse sequence, whose amplitude is below a predetermined threshold and the second test vector is a second pulse train whose amplitude is above is the threshold. This ensures very easy that both the states "light path free" (amplitude over the threshold value) and "light path interrupted" (amplitude below the threshold). According to the Previous embodiments, it is preferably provided that the pulse train of the first test vector and the pulse train of the second one Test vector are sent alternately.

Prefers the pulse train has at least three individual pulses per light receiver on. By using three single pulses per pulse group On the one hand, the momentum group is sufficiently short to be fast Signal processing of the control and evaluation to ensure and on the other hand, sufficiently significant to eliminate these from glitches, which are caused, for example, by stray light, to distinguish. From the monitoring unit will end of the above-mentioned cycle, the first test vector with three Single pulses sent, each below the threshold and then the second test vector with three single pulses, each over are the threshold. To be robust against interference signals to be, and an availability of such interfering signals to ensure that a "two from three evaluation "of the individual pulses. there only two of the three individual pulses must be detected. Only if only a single pulse or more than three Single pulses are detected, the pulse train is considered not properly detected.

In Development of the invention has the monitoring unit Means open to intermediate signals of the control and evaluation unit, which depend on the test vectors, with intermediate expectation values to compare the monitoring unit. This will be on other outputs of the control and evaluation unit intermediate signals supplied to the monitoring unit with these to compare further expectation values. This makes it possible to limit an error that has occurred to specific modules. This results in a better diagnosis of the optoelectronic sensor allows.

In In a particular embodiment, the control and evaluation unit and the monitoring unit via an interface interconnected to perform cross comparisons. As a result, the control and evaluation unit can also check whether the monitoring unit is a proper Function fulfilled by, for example, a dynamic Signal identifier cyclic from the monitoring unit to the Control and evaluation is sent. About the interface can also initialization data for the test vectors to be used be replaced. Change, for example, the received signals the light receiver due to a changed pulse train the transmitter, the test vectors used can be changed to this Pulse sequence to be adjusted. Through a data exchange between Control and evaluation and monitoring unit can Target and actual data at every point in time and in every processing step compared with each other in terms of monitoring become.

The control and evaluation unit or the monitoring unit are formed by a digital signal processor, a microcontroller, an application-specific integrated logic (ASIC), a field-programmable gate array (FPGA), a complex programmable logic (CPLD) or a programmable array logic (PAL). In this case, the control and evaluation unit is particularly preferably formed by a digital signal processor and the monitoring unit is formed by a microcontroller, because the power requirements for the monitoring unit are much lower than for the control and evaluation unit. The evaluation unit continues to be designed as a powerful FPGA or ASIC. This has the advantage that the complex signal processing for fast signal processing is provided directly in integrated circuits. The monitoring unit is preferably designed as PAL or GAL with reduced functionality. This reduces the cost of the monitoring unit, since such integrated circuits are much cheaper than, for example, a microcontroller.

Preferably the optoelectronic sensor is designed as a light grid, wherein Light transmitter and light receiver in a housing are housed and a first and second housing opposite are arranged. The light emitter and light receiver in the first housing form with light receivers and light emitters in the second housing each transmitter / receiver pairs. This allows the evaluation unit and monitoring unit in identical design can be provided in both cases. In each case, a switching output of each case becomes a common two-channel switching output of the light grid merged.

In an alternative embodiment is the optoelectronic Sensor also designed as a light grid, but now in the first housing only light emitter are accommodated and in the second housing exclusively Light receiver. The individual light emitters form again with the individual, each opposite light receivers each transmitter / receiver pair. This alternative has the Advantage that only in the housing with the light receivers the control and evaluation unit and the monitoring unit must be provided. The housing with the light transmitters has, however, a less expensive control unit, as only the light transmitter must be controlled.

Also during the test by means of the test vectors have both the control and evaluation unit as well as the monitoring unit the possibility to deactivate a switching output. The means, all parts of the program stay during one Testing active.

in the The invention is based on exemplary embodiments explained in detail with reference to the drawing.

In the drawing shows:

1 a schematic representation of an optoelectronic sensor according to the invention;

2 a block diagram for displaying an evaluation;

3 a signal diagram with signals of the light receiver;

4 a signal diagram with test vectors.

1 shows a light grid 2 with a first housing 22 and with a second housing 24 , In each of the housings 22 and 24 are each light transmitter 6 and light receiver 4 accommodated. The light emitter 6 are in a first Grup pe successively arranged in a row and the light receiver 4 arranged in a second group in the same row also in succession. The light emitter 6 and light receiver 4 in a housing are operated in a common optical shift register chain, which is hereinafter referred to by the term optical chain SUEE. The light emitter 6 and light receiver 4 are controlled and evaluated by a common control and evaluation unit AE. To check the light grid function, a monitoring unit UE is provided, as will be explained in more detail below.

In the second housing 24 which is the first housing 22 are arranged opposite each other, are the light emitters 6 or light receivers 4 corresponding light receiver 4 or light emitter 6 accommodated, so that opposite light emitter and light receiver respectively form transmitter / receiver pairs and thus individual light barriers of the light grid. Such light grid 2 are used to create optical protective fields necessary to secure hazardous points. If a protective field is violated, for example by an intervention of a person and thus interruption of at least one of the light barriers of the light grid, then a switching unit SE is correspondingly activated to output a switching signal in order to switch off a dangerous movement of a dangerous machine.

In such light grids 2 It may also be provided that in the first housing 22 only light emitter and in the second housing 24 the associated light receivers are arranged.

So these light curtains 2 can be used in the field of accident prevention, the light grids 2 comply with relevant standards and safety regulations. An important prerequisite for a prescribed fault tolerance is that occurring faults within the optoelectronic sensor can be controlled, which means that the faults must not lead to a dangerous failure or condition. Occurring errors must not remain undetected, but must be detected by an error detection. Especially kri Table errors must be detected within a specified response time or response time.

2 shows a block diagram for illustrating the evaluation in a light grid according to the invention 2 with the control and evaluation unit AE and the monitoring unit UE for detecting possible errors occurred. The optical chain SUEE is essentially controlled with four different signals or evaluated. First, a signal BEAM is provided to individually activate respective light emitters or photoreceivers. Another signal SHIFT is necessary to select a particular light emitter or receiver, or to switch from a particular light receiver to a next light receiver. Another signal SERRET indicates when the end of the optical chain has been reached, that is, whether the last optical element in the optical chain has been driven in one cycle. A reception signal REC corresponds to the light reception of a light receiver. The optical chain SUEE is preferably controlled according to the principle of a shift register structure. In a cycle, the respective light emitter and / or light receiver are controlled one after the other. It could alternatively also be provided that in each case a light transmitter and a light receiver of an optical chain are activated simultaneously, so that the light emitter and light receiver of an optical chain are switched through in parallel.

The Control and evaluation unit AE essentially checks whether the received signal REC is sufficiently identifiable and for each receiver the received signal REC the transmitted signal corresponds to a corresponding light transmitter. If so, then is, the light path is free and there is no object in the Light path. After one cycle, the control and evaluation unit AE thus determine whether the protective field is injured. Is for a receiver does not receive a received signal REC, is the protective field is interrupted at the appropriate place, so that receive no light from a corresponding light receiver could be.

Dependent The control and evaluation unit AE inputs from this evaluation Signal to the switching unit SE off. Depending on this Signal is by means of a switching signal of the switching unit SE a connected machine control released when the protective field is free, or a dangerous movement is stopped, if the protective field is interrupted. In the evaluation of the protective field the control and evaluation unit AE also different, known Operating modes, such as contactor control, restart interlock or account for certain areas of the protective field.

The monitoring unit UE is provided for checking the correct functioning of the control and evaluation unit AE. For this purpose, it is provided that the monitoring unit UE via an output 8th at least two different test vectors 26 and 28 as signals UEout / AEin to the control and evaluation unit AE and that via the input, at which the reception signals REC are present. The control and evaluation unit AE thus receives the received signal REC ( 3 ) and the test vectors as signal UEout / AEin on the same input or at the same input interface. The control and evaluation unit AE can not differentiate between received signals REC of the light receivers or the test vectors of the monitoring unit UE.

Furthermore, the monitoring unit UE has an input 10 to output signals UEin / AEout of the control and evaluation unit AE, which depend on the test vectors 26 and 28 were generated, to be able to read. The monitoring unit UE now compares by means of comparison means 12 the read-in output signals UEin / AEout of the control and evaluation unit AE with stored expected values. If the read-in output signals UEin / AEout correspond to the expected values, then there is a proper function of the control and evaluation unit AE and no errors have occurred in the control and evaluation unit AE. However, if the output signals UEin / AEout do not agree with the expected values, then the control and evaluation unit AE malfunctions and the monitoring unit UE can influence the switching unit SE via a further output so that the switching unit SE can react accordingly, for example by means of the switching signal to disable the dangerous machine or at least a dangerous movement.

The function of the monitoring unit UE is restricted in the case of the optoelectronic sensor according to the invention only to checking the generated output signals UEin / AEout of the control and evaluation unit AE as a function of the test vectors 26 and 28 and the ability to control the switching unit SE. As a result, the monitoring unit UE can be carried out very simply, as a result of which the expenditure for the monitoring unit UE is minimized. Thus, in the simplest case, the monitoring unit UE can consist of a very simple integrated circuit.

3 shows a part of the signals of the optical chain in a signal diagram. Corresponding in 2 Also shown signals are provided with the same reference numerals. 3 shows only a partial time segment of the signals during the control of the optical chain. The signal SERRET indicates whether one end of the optical chain has already been reached is. As long as this assumes the logic level zero, one end of the optical chain is not reached in a sequential control. The signal SHIFT is formed as a double pulse control signal from the control and evaluation to the optical chain to switch from a light receiver to the next light receiver. That is, in the section B shown, a first light receiver is active and in the subsequent section C, a second light receiver.

The signal REC shows the received signals of a respective light receiver or the signal that is sent from the light receivers to the control and evaluation unit AE. When the light emitters, as in the embodiment, emit three single short light pulses, they are also received as individual pulses from a light receiver, which is shown in FIG 3 can be recognized as a signal REC. The individual pulses of the signal REC in sections B and C exceed a set signal threshold with a normalized threshold value of 0.75, whereafter the light beams are recognized by the control and evaluation unit as free light beams, ie uninterrupted light beams. For sufficient identification of a received light beam, however, it is sufficient if only two of the three pulses are detected ("two out of three evaluation"). Whether a light beam is regarded as free or interrupted is decided by the control and evaluation unit and, if appropriate, the switching unit SE is activated accordingly.

4 shows another signal diagram showing the signals of the optical chain at a later time, wherein the last element of the optical chain, so the last light receiver of a cycle was controlled. The signal SERRET indicates a level 'one' after activation of the last light receiver. Starting from this signal SERRET signal for indicating the end of the optical chain, which is also supplied to the monitoring unit, the monitoring unit UE in each case successively outputs the two different test vectors 26 and 28 in the control and evaluation as a signal UEout / AEin on the line on which the received signal REC to the control and evaluation unit AE is performed. The first test vector 26 consists of a first pulse train 14 with three single pulses as shown in section E. The three individual pulses have a peak value of 0.5 for simulating an insufficiently received signal since the amplitude is below the threshold of 0.75 for simulating an uninterrupted beam of light. In a further section F, the control and evaluation unit AE becomes the second test vector 28 supplied, consisting of a second pulse train 14 with three individual pulses, which have a maximum value of 'one', for the simulation of a properly received signal received, ie simulation of a free light path.

The two test vectors 26 and 28 be treated by the control and evaluation unit as two real received signals corresponding light receiver, because the control and evaluation unit can not distinguish the signals applied to the same input signals REC and UEout / AEin. For the first test vector 26 If the function is correct, the control and evaluation unit outputs an output signal UEin / AEout with the value '0' and for the second test vector 28 an output signal UEin / AEout having the value '1'. The output signal UEin / AEout is read in and evaluated by the monitoring unit. Since the monitoring unit UE the test vectors 26 and 28 itself, the threshold values are known to it, and the monitoring unit UE then generates an expected value of "0" according to the test vector 26 and an expected value "1" according to test vector 28 , If the control and evaluation unit operates without error, the output signal values UEin / AEout correspond to these expected values. The monitoring unit UE performs a comparison of these values by means of a comparison unit 12 by. If there is a deviation, the control unit SE controls the switching unit accordingly, so that a dangerous movement is stopped. This is the case, for example, if, due to the entered test vectors 26 and 28 In both sections E and F, respectively, an output signal UEin / AEout with the value '1' or in both sections an output signal UEin / AEout with the value '0' or other different output signals UEin / AEout would occur at the expected values.

The evaluation unit checks the received signal REC 3 and the signal UEout / AEin during each cycle of the optical chain. However, in order to avoid switching errors due to very short interruptions of light beams, only signals are regarded as a shutdown signal, which occur in two cycles in a row at a respective light receiver. To generate a switch-off signal, it is therefore necessary for a light receiver to be covered for at least two cycles. The test vectors 26 and 28 according to 4 In this case, the control and evaluation unit are alternately supplied in each case, that is, in the first cycle, first the first test vector 26 and then the second test vector 28 generated and tested and in the second cycle, first the second test vector 28 and then the first test vector 26 , As a result, the evaluation unit is constantly monitored and even dynamically due to the permutation of the test vectors.

2

light Curtain

4

light receiver

6

light source

8th

output

10

entrance

12

comparison means

14

pulse train

16

switching threshold

18

Single pulse

20

interface

22

first casing

24

second casing

26

first test vector

28

second test vector

B C, E, F

sections

AE

Tax- and evaluation unit

UE

monitoring unit

SE

switching unit

Süe

Transmission / reception chain, optical chain

SERRET

signal

SHIFT

signal

REC

signal

UEin / AEOUT

signal

UEout / AIN

signal

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 69225487 T2 [0004]

Cited non-patent literature

• - EN / IEC 61496 [0002]
• - EN 61508 [0002]
• - EN 954 [0002]
• - EN 13849 [0002]

Claims (11)

Optoelectronic sensor, in particular light grid ( 2 ) with at least one light transmitter ( 6 ) for emitting light pulses, with at least one light receiver ( 4 ) for receiving the transmitted light pulses, with a control and evaluation unit (AE) for controlling and evaluating at least the light receiver ( 4 ) and a monitoring unit (UE) for checking at least the function of the control and evaluation unit (AE), wherein the control and evaluation unit (AE) is diversified to the monitoring unit (UE) and the control and evaluation unit (AE) and the monitoring unit (UE) are connected to a switching unit (SE) for outputting a switching signal, characterized in that the monitoring unit has at least one output ( 8th ), which is connected to the control and evaluation unit (AE), for outputting at least two different test vectors ( 26 . 28 ) to the control and evaluation unit (AE) and at least one input ( 10 ), which is connected to the control and evaluation unit (AE), for reading an output signal (UEin / AEout) of the control and evaluation unit (AE), which of the test vectors ( 26 . 28 ) and in the monitoring unit (UE) comparison means ( 12 ) are provided to compare the output signal (UEin / AEout) with at least two different expected values and the switching unit (SE) is driven depending on a result of the comparison. Optoelectronic sensor according to one of the preceding claims, characterized in that the test vectors ( 26 . 28 ) are output alternately. Optoelectronic sensor according to one of the preceding claims, characterized in that the test vectors ( 26 . 28 ) are formed by analog and / or digital signals. Optoelectronic sensor according to one of the preceding claims, characterized in that a test vector ( 26 . 28 ) a pulse train ( 14 ), whose shape is approximately identical to a received signal of a light receiver when receiving light. Optoelectronic sensor according to one of the preceding claims, characterized in that a first test vector ( 26 ) a first pulse sequence ( 14 ) whose amplitude is below a threshold ( 16 ) and a second test vector ( 28 ) a second pulse train ( 14 ) whose amplitude is above the threshold ( 16 ) lies. Optoelectronic sensor according to one of the preceding claims, characterized in that the pulse sequence ( 14 ) has at least three individual pulses per receiving element. Optoelectronic sensor according to one of the preceding claims, characterized in that the monitoring unit (UE) comprises means for intermediate signals of the control and evaluation unit (AE), which of the test vectors ( 26 . 28 ), compare with intermediate expectancy vectors of the surveillance unit (UE). Optoelectronic sensor according to one of the preceding Claims, characterized in that the control and Evaluation unit (AE) and the monitoring unit (UE) via an interface are interconnected to perform cross comparisons. Optoelectronic sensor according to claim 1, characterized in that the control and evaluation unit (AE) or the monitoring unit (UE) through a digital signal processor, a microcontroller, a application specific integrated logic - ASIC, a field programmable Gate Array - FPGA, a complex programmable logic - CPLD or a programmable array logic - PAL is formed. Optoelectronic sensor according to one of the preceding claims, characterized in that the optoelectronic sensor as a light grid ( 2 ), wherein light emitters ( 6 ) and light receiver ( 4 ) in each case ( 22 . 24 ) and a first and second housing ( 22 . 24 ) are arranged opposite one another, wherein light emitter ( 6 ) and light receiver ( 4 ) of the first housing ( 22 ) with light receivers ( 4 ) and light emitters ( 6 ) of the second housing ( 24 ) each form transmitter / receiver pairs. Optoelectronic sensor according to one of the preceding claims 1 to 7, characterized in that the optoelectronic sensor as a light grid ( 2 ), wherein light emitters ( 6 ) in a first housing ( 22 ) and light receivers ( 4 ) in a second housing ( 24 ) and the first and second housings ( 22 . 24 ) are arranged opposite one another, wherein light emitter ( 6 ) with light receivers ( 4 ) each form transmitter / receiver pairs.