FR2584550A1 - PROXIMITY SENSOR - Google Patents

Abstract

STATIC PROXIMITY DETECTOR CONTAINING THE FOLLOWING FUNCTIONAL UNITS GROUPED IN AN OPERATING CIRCUIT: A PROXIMITY DETECTOR 10 (INDUCTIVE-CAPACITIVE), A CIRCUIT ELEMENT 11 PREPARING THE SIGNALS INTENDED FOR THE SENSOR (CIRCUIT FORMING PULSE AND PULSE ENDS 13) GENERATION OF A USEFUL SIGNAL AND WITH OR WITHOUT SHORT-CIRCUIT PROTECTION CIRCUIT 12, CHARACTERIZED IN THAT CIRCUIT ELEMENTS 10, 11, 13 AND POSSIBLY 12 COOPERATING IN AN OPERATING CIRCUIT, ARE CONNECTED IN A CONTROL CIRCUIT 20 INTEGRATED WITH THE DETECTOR TO FORM AN ADDITIONAL CONTROL CIRCUIT.

Description

-1

  The invention lies in the field of communications

  electronic sensors and has for its object a modification of an inductive proximity detector of known basic construction, to make it a proximity detector

  inductive signaling its own operation.

  Static switches are electronic detectors that have two defined states, at which

  is controlled by a "low" or "high" logic signal. The commu-

  State-to-state is used to trigger or indicate a new state. Detectors of this type are used for example in production lines and are used to monitor machine elements and / or to sort parts of products. The installation is based on the proper functioning of the detectors; an undetected malfunction of a single detector can cause significant faults. To remedy this, it is sought to increase the reliability of the detector in the direction of high MLTBF values (average time between failures) and / or to monitor the authorized / unauthorized operating states of the detector and to report or

  to repair the detected malfunction. -

  The objective pursued by the invention relates to this second aspect of surveillance and aims to produce a static proximity detector indicating its own operation and its own possible failure,

  avoiding to intervene actively in the operation.

  This object is achieved in that a

  known inductive proximity, protected against short-

  circuits and fixed polarity, is modified so as to deliver a signal to an indicator output when there is an irregular operating condition; for example for the following states: short-circuits or interruptions at the output of the detector, erroneous level at the output of the oscillator, malfunction of the excitation stage (for example of the Schmitt discriminator), power cut, break the test line, etc. The modification according to the invention is characterized in that the circuit elements cooperating in an operating circuit are connected in a control circuit integrated into the detector for

  form an additional control circuit.

  The proximity detector equipped according to the invention is fully controlled, in the attenuated state or in the non-attenuated state. During ON / OFF or OFF / ON switching, only reduced control is possible. The time reports are generally such that this transition does not cause loss of reliability. When using the detector described here

  with very clear switching states, the use

  has a fully self-controlling switch

  rement which immediately delivers to the test output any malfunction and this actively, without the need to invite it from the commands and without an electronic command line

exterior is required.

  Various other features stand out

  moreover from the detailed description which follows.

  Two embodiments of the invention shown by way of nonlimiting example to the annexed circuit diagrams to which: FIG. 1 is a complete proximity detector, self-checking, equipped according to the invention, FIG. 2 represents a first embodiment of a control circuit, FIG. 3 represents a second embodiment of a control circuit, and FIG. 4 is a relative structural diagram

in the second embodiment.

  An ordinary proximity sensor, inductive, short-circuit protected and of fixed polarity, generally includes an oscillator, a signal generator circuit, a final (power) stage and a short-circuit protection. These functional groups are grouped together in FIG. 1, in a functional block 1, the detector proper, which includes the oscillator 10, a Schmitt discriminator 11 preparing the signal for the oscillator and a final power stage 13 controlled by this Schmitt discriminator. The final stage is located in a short-circuit protection circuit 12 which, during a short-circuit, blocks the Schmitt discriminator as a signal generator. Here is how one can describe in a simplified way an embodiment, given by way of example, of a known static proximity detector. A switch 1 of this type is modified according to the invention by a monitoring circuit 20 integrated into the switch, which represents, in a second functional block 2, the control circuit. It is assumed in this case that in order to use a "control signal", a final stage or an excitation stage is needed at any point on the circuit. For clarity, such a final stage 21 has been shown in the functional block 2 for checking the detector,

  although it is not essential to the invention. Detection

  self-checking proximity sensor, has, internally

  gration of the control circuit, of a second output

  alarm A2 in addition to the usual output A1 of the

  mutator. The control circuit 20 has several control lines E1, E2, E3, E4, etc., and an output A to which an alarm signal appears in the event of a malfunction of the proximity detector or of the unit not shown. here, mounted at output Al. This signal indicates a faulty operating state of the proximity sensor itself, as well as the switching state of the proximity sensor which, for example, signals a fault in the controlled system

  by detectors, for example in a manufacturing chain

  cation. This proximity sensor not only monitors its own internal function, but also

also his own activity.

  In the example of control circuit 20 described here, the output signals of the oscillator unit 10 are additionally sent to an input El. At another input E2, there is the output signal of the protection circuit against short circuits 12 which indicates the short circuit state YES / NO. Another input E3 sends the output signals of the Schmitt discriminator 11 to the control circuit 20, for the control control of the final stage 13 and another input E4, connected to the output of the final stage 13, directs the circuit

  monitoring of the switching status of the proximity detector

  moth. It will be explained in detail in the two exemplary embodiments below the way in which the control lines E1 to E4 and their signals are connected to each other in the control circuit 20. But first, a few remarks will be made about the

different signal detections.

  The bistable output signal from a static proximity sensor is the product of a relatively complex process of detecting and generating signals using a sophisticated analog technique. The two simple ON / OFF output states are not able to indicate a malfunction; MARKET

  may be right or wrong, STOP may be right or wrong.

  We cannot therefore expect a priori from the output signal

  of the switch that it provides a perfect indication.

  However, we rely on the ON / OFF states of detectors

  "to control machines or installations

  Complete relationships in a manufacturing process strategy, when one of the two states appears on the detector. When we examine the switch in terms of operating technique, we find among different functional elements, so-called undefined states which cause a defined output state OFF or ON, for example the faulty operation of the Schmitt discriminator while the other functions are intact, etc. This faulty operation cannot be read at the output of the Schmitt discriminator, any more than at the output of the "blocked" detector, and can only be detected when the general operation is faulty. Information is still missing which, in conjunction with faulty operation, causes

  appear faulty behavior.

  For switch self-checking, the

  different functional elements of it which usual-

  are only connected to each other in an operating circ-it, must also be connected in

  a control circuit which has the role of making

  to know the truth. This connection is made by means of the control circuit 20, its output A or A2 indicates

  the truth of the operating output A1.

  The control circuit in the example shown in FIG. 1 includes the information: E1, E2, E3, E4, ... En, and their combinations such as Et / E2; E1 / E3; E1 / E4; E2 / E3; E2 / E4; E3 / E4; E1 / E2 / E3; E1 / E2 / E4; E2 / E3 / E4; E1 / E2 / E3 / E4, etc. commutatively. To represent the certain state, it is not necessary to use each element of the quantity of information. According to the type of operating circuit of a switch, the content of the information available varies, this being always sufficient according to the invention for a circuit

  planned control. The two embodiments above

  next show in addition to two possible logical links, two different hardware implementations, a fixed wired form and an insertable form

in a programmable circuit.

  FIG. 2 shows a first embodiment

  tion of a control assembly of the signals described with reference to FIG. 1 and of the control lines E1 to E4, or up to En in the case of other elements of

  control such as thermal detectors 32 and / or detectors

  pressure sensors 33 in the proximity sensor

1, see figure 1.

  It is also possible to use a humidity sensor 34, to replace the other control elements or with them. The output of the oscillator is connected to a window comparator 22 comprising two windows for authorized H / B ranges, for controlling the level of the oscillator signal. The level information does not, however, provide information on the dynamics of the oscillator whose changing states have yet to be detected. This detection is carried out in a circuit composed of a monostable multivibrator 25 comprising a timer and an XOR circuit 26. At the output 22A of the window comparator 22, signals should appear alternately for the two levels. A small memory formed by the monostable multivibrator 25 at the output 25A of which the old state is still found, checks whether the succession is indeed alternative and whether the level remains high or low. If the "past" is equal to the present at the exit 22A, it will be necessary to admit

  that the oscillator was stuck at one level. It appears

  is due to an XOR circuit mounted downstream to see it

  by performing the comparison each time and deli-

  at its output 26A a 1 * signal for "oscillator oscillates". In the operating circuit, the oscillator signal is sent to the Schmitt discriminator 11 which gives the oscillator signals the form of defined square signals. The signals could then be used at this time in the E1 / E4 control lines. But since the signal of the Schmitt discriminator is reproduced directly or inversely by the final stage 13, one can, as it was said above, have recourse to another element of information, namely E2 for the signal of the discriminator of Schmitt and E3

  for the amplified signal of the Schmitt discriminator.

  In this example, the signal is inverted during amplification; if this is not the case, the final stage does not work. For the control assembly of the control lines E2 and E3, an XOR circuit 23 is used, the output 23A of which outputs the signal 2 * XOR3 * for "signal of the amplified Schmitt discriminator". This information also does not provide information on the dynamics. For example,

  in the case of a short circuit, the charge of the

  The Schmitt sensor suspended from the detector is maintained by the short-circuit protection circuit 12 (Figure 1) and the expected reverse state is static, but not necessarily inaccurate. A similar memory circuit, as described in relation to the control of the oscillator, uses a signal from the output of the short-circuit protection circuit 12 at the input E4 of the control circuit 20. E4 drives a multivibrator monostable 24, the second state of which is kept stable for a fixed period. This

  dynamic state appears at output 24A of multivibra-

  monostable sensor 24 in the form of the 4 * signal which indicates in the event of a short circuit only, one of the stable states

of the multivibrator.

  The signals of the outputs 23A, 24A, 26A give in a circuit T a signal for "correct operation of the switch" or "failure". In the event of a short circuit check, these do not refer only to the switch, but also to its output state which can also indicate a fault, for example in the production chain. 1 * signals for

  "oscillator works" ', 2 * XOR3 * for "discrimination signal

  amplified Schmitt timer "and 4 * for" no short

  circuit ", are grouped in a NAND circuit 27 for the output signal A which indicates regular operation only in the presence of the three qualification characteristics. The other state indicates a fault, without however identifying it This is however possible

  if in addition to the signal T, the different states are indicated.

  After this very detailed description of a

  embodiment using discrete components, and so that the idea behind this is

  very clear, an embodiment will be described below

  tion "intelligent" with reference to Figure 3 which makes

  call to a processor and to memory means.

  Starting from the same operating circuit as that of the detector according to FIG. 1, the control circuit 20 according to FIG. 3 shows the control lines E1 to E4 which lead to an operating circuit, here to a digital circuit 30. This circuit shown

  as a single functional block has a process

  memory and memory as well as additional or resident software. While in the embodiment according to FIG. 2, the logic circuits are produced with discrete switching means, this is not the case with the active implementation with microprocessor. All static and dynamic states are processed by the processor. The control circuit, with the exception of essential hardware, thus depends on the software and is clearly more differentiated, with barely greater circuit complexity. The output of a line exciter bus 35 is connected to an alarm bus which receives, for example from the operating circuit, from the digital circuit 30, words in series, for example 8-bit words which can be directly associated

the cause of the failure.

  The structural diagram of FIG. 4 shows an embodiment of the microprocessor solution according to which a proximity detector equipped with a

  microprocessor can operate according to the invention.

  At the start, that is to say after switching on the operating circuit, an initialization routine is executed, which is designated by INIT. It includes, for example, memory erasure, register loading, reset, alarm output, editing of error message 0, etc., that is to say the achievement of a basic state. A subroutine can still execute a self-test in order to define the basic state. From the INIT routine, the operation passes to an endless loop, designated by LOOP. This endless loop establishes a state comparable to the first embodiment in which the analogous connections are connected in parallel to a control circuit "constantly present" in time. LOOP therefore replaces the simultaneous interrogation carried out in the first embodiment. The module causes the control lines El to En to be stored in memory and the processing of information El, E2, E3, E4 ... En, and their combinations such as El / E2; E1 / E3; E1 / E4; E2 / E3; E2 / E4 E3 / E4; E1 / E2 / E3; E1 / E2 / E4; E2 / E3 / E4; El / E2 / E3 / E4, etc., commutatively. See also

  the first example made with discrete means.

  The connections selected or predetermined by the analog input program and the conditions that the link must meet are checked in the

  next module 50. A level comparison or comparison

  its state sound sorts out the defective states, while the different information of the output quantities

  assembled to form a new condition, does not disappear

  unlike the analogous solution of the

  first embodiment, but remain in memory.

  This makes it possible to identify the cause of the failure, so that one can indicate not only its state, but also its "address" at the output of bus 35. The module 60 finally determines the edition of a message d 'fault,

  by eXample (F7, F6, F5, F4, F3, F2, Fl, F0) = (10010001), that is-

  that is, the defective state is generated by faults F7, F4, F0. F7 to F0 is defined by convention and depends

  of the above links El ---- En and their conditions.

  An additional search is possible in module 40 if for example the analog input Ei is compared with a threshold 1 for one state and with a threshold 2 for the other state. We can thus also see the threshold state 1 <Ei <Threshold 2 and define it as the transition state U, that is to say the state in which the proximity detector switches. If the transition state has just occurred, there is no fault, otherwise the previous correct state must be considered for the YES / NO fault decision to be taken. The transition state of the proximity detector has also been described in relation to the first embodiment. l1 2584550

Claims (9)

  1. Static proximity sensor comprising the following functional units grouped into an operating circuit: a proximity sensor (10) (inductive / capacitive), a circuit element (11) preparing the signals intended for the sensor (pulse forming circuit ), with a final stage (13) for generating a useful signal and with or without a short-circuit protection circuit (12), characterized in that the circuit elements (10,11, 13 and possibly 12 ) cooperating in an operating circuit, are connected in a control circuit (20) integrated into the detector to form an additional control circuit. 2. Switch according to claim 1, characterized in that the control lines (El, E2, E3, E4) are connected, for the control circuit (20) to the outputs of each functional unit of a proximity detector comprising a oscillator circuit (10), a pulse forming circuit (11), a final stage (13) and a short-circuit protection circuit (12),   3. Switch according to claim 2, charac-   in that the control circuit is made up   a window comparator (22) with a first multi-   vibrator (25) mounted downstream and a first XOR circuit (26) connected to the outputs of the window comparator (22) of the first multivibrator (25) to deliver information to the oscillator (1 *); and a second XOR circuit (23) for delivering information (2 * / 3 *) from the pulse-forming circuit (2 *) and from the final stage (3 *); and a second multivibrator (24) to deliver short-circuit protection information (4 *) and an AND circuit element (27) to connect information (1 *, 2 * / 3 *, 4 *).   4. Switch according to claim 1, charac-   terized in that the control lines (E1, E2, E3, E4) of the control circuit (20) are connected to the outputs of each functional unit of a proximity detector comprising an oscillator circuit (10), a circuit pulse generator (11), a final stage (13) and a circuit   short circuit protection (12).   5. Switch - according to claim 4, characterized in that the control circuit (20) comprises a processor and a memory and presents at its output (A) messages intended to identify a cause of failure.   6. Switch according to claim 1, charac-   characterized in that monitoring elements (31, 32, 33) are used in the detector (1) in addition to   functional units of the operating circuit.   7. Switch according to claim 6, charac-   terized in that additional control lines (En-ln, En) and a control circuit (20) are provided to constitute the additional control circuit   surveillance elements (31, 32, 33).   8. Switch according to claim 7, charac-   terized in that a pressure detector (33) and / or a temperature detector (32) are used in   the control circuit (En-1, En, 20).   9. Switch according to one of claims   7 or 8, characterized in that a humidity detector (31) is used in the control circuit (En-l, En,).