DE4122635B4 - Device for defect detection in sensors - Google Patents

Abstract

Facility for defect detection in sensors, preferably differential inductive sensors, with an evaluation circuit that provides a signal that as an actual value for one Control device is used, the evaluation circuit when occurring an error provides a constant output signal, characterized that a defect then it is recognized. if the actual value is within a specifiable Range lies and the controller at the same time during a specifiable longer Time at one of his stops located.

Description

The The invention relates to a device for defect detection in sensors, preferably differential inductive sensors according to the preamble of the main claim.

Such Sensors, including an associated one Evaluation circuit are usually used to capture adjustment paths of components, this can Be adjusting in rotary or linear movements. Usual inductive Differential sensors are, for example, half-differential short-circuit ring sensors or differential throttle sensors.

at such sensors are generally due to the symmetry Difficulty that with broken supply line at the center tap in the evaluation circuit is generated a constant DC voltage, their height the usual Does not leave the measuring range, so that a mistake is not easy with the help of a so-called signal range check can be recognized. To detect such a mistake, therefore, must another error detection will be performed.

From the DE 39 27 833 C2 a differential throttle displacement sensor is known, which has a series connection of two inductors whose value is the same in the middle position. As the part to be measured moves, one of the inductors becomes smaller and the other larger.

The two inductors are excited by high frequency alternating voltage, at the connection of the two inductors the measuring signal is removed, in the subsequent evaluation circuit is processed for position detection. The known sensor arrangement Although very accurate, it has the disadvantage of being interrupted one of the supply lines can lead to erroneous measured values.

A device for measuring distance with the aid of an inductive sensor, in which it is detected in a monitoring circuit arrangement whether an error occurs in the sensor itself or in one of the supply lines, is known from the preamble DE 28 05 876 C3 known. In this known device, in particular, it is checked whether the signal voltage, for example when a supply line is interrupted or when a short circuit occurs, leaves a predeterminable range. However, this known device can not detect an error when the output voltage does not leave the permitted range in the presence of special circumstances.

From the DE 40 15 960 A1 is a device for defect detection in sensors known. In this case, an actual value is monitored to see whether it lies within a predefinable range. However, it is not checked whether a controller is at the same time for a predetermined time at one of his stops.

Advantages of the invention

The inventive device for defect detection in sensors with the characteristic features The main claim has the advantage that by linking two Conditions whose existence is not simultaneous during a long time possible is, the error or defect is detected. It is a simple one Error detection possible.

By in the subclaims specified measures If other advantages can be achieved, it is possible, for example cause an error to trigger an ad and actions to influence the Make regulator so that no unacceptable operating conditions may occur.

Advantageous is still, the actual value in addition then monitor whether it lies within a possible range under the given circumstances (signal range check).

Especially can be advantageous the inventive device in conjunction with an inductive exhaust gas return indicator.

drawing

One embodiment The invention is illustrated in the drawing and will be described in the following Description closer explained. The single figure in block symbols shows a monitoring device according to the invention for one differential inductive sensor.

description of the embodiment

A differential inductive sensor 10 For example, a Abgashubrückmelder, consisting of the inductors L1 and L2 and a movable part 11 exists, serves as an actual value transmitter for a subsequent controlled system. The two inductors L1 and L2 are connected in series and are at an oscillating voltage with the peak values + U and -U.

The connection point of the two inductors L1 and L2 is an evaluation circuit 12 connected, at whose output the actual value arises. The evaluation circuit 12 is shown in the embodiment as separated from the sensor, but it can also be part of the sensor 10 be.

The exit 13 the evaluation circuit 12 , is with an input of the regulator 14 connected, via another input is the controller 14 the desired value is supplied.

A first output of the regulator 14 leads to an actuator 15 that is centered or directly on the moving part 11 of the sensor 10 acts. A second output of the regulator 14 leads to a logical circuit 16 , from this logic circuit 16 leads another connection to the controller 14 back.

Furthermore, the evaluation circuit 12 about her exit 13 where the actual value arises, with the logic circuit 16 whose second output is on an error display 17 leads. The differential inductive sensor 10 is fed with two anti-phase voltages, preferably square-wave voltages, constant frequency and amplitude, in the figure this is represented by + U and -U. In the position of the movable part shown in the figure 11 the two inductances L1 and L2 are equal, with a displacement of the movable part 11 In the direction of the arrow, the inductance L2 becomes smaller, while the inductance L1 becomes larger by the same amount.

The voltage between the two inductors L1 and L2 changes depending on the position of the movable part 11 , wherein the amplitude of this voltage is approximately proportional to the difference between the two inductances L1 and L2.

Through the evaluation circuit 12 this voltage is further processed in a suitable manner, so that at the output 13 this evaluation circuit 12 an evaluable actual value arises.

This actual value, as well as a setpoint value, becomes the regulator 14 fed, in which the usual comparison operations between the setpoint and actual value and the run via the actuator 15 ultimately on the moving part 11 so that its position is properly regulated.

The position of the moving part 11 at the output of the evaluation circuit 12 generates a corresponding actual value, should now according to the invention together with the output of the controller 14 be monitored for plausibility and used for error detection in the control system or in the sensor itself. This is both the output 13 the evaluation circuit 12 resulting actual value and the starting position of the controller 14 the logic circuit 16 fed. In this logical circuit 16 the two values are compared with each other, an error is detected when the actual value is within a predeterminable range and the controller is simultaneously at a stop for a predeterminably longer time. This predeterminable range is set to include all possible values at the output 13 the evaluation circuit 12 can arise when the supply line is interrupted, so it is located approximately in the middle of the working range of the sensor. The error detection is possible because on the one hand, if the controller is at one of his attacks, the actual value would have to change after some time and thus leave the specified range and on the other hand, a controller stop should not occur, as long as the actual value within the predetermined range is located around the center of the work area.

When detected fault or defect of the logic circuit is an indication 17 triggered, further provided that in this case by the logic circuit 16 a control of the controller 14 such that the controller 14 over the actuator 15 the moving part 11 moved to an uncritical position.

The logic circuit 16 can be designed in analog circuit technology or as a microprocessor, the display 17 as a lamp, LED or as an acoustic device. The arrangement shown in the figure can be used for any differential inductive sensors.

Claims (4)

Device for detecting defects in sensors, preferably differential inductive sensors, with an evaluation circuit which supplies a signal which serves as the actual value for a control device, wherein the evaluation circuit provides a constant output signal when an error occurs, characterized in that a defect is then detected , if the actual value lies within a predefinable range and the regulator is at one of its stops for a preselectably longer time at the same time. Device according to claim 1, characterized that at detected error is a display and / or action to influence the controller done in such a way that no Inadmissible operating conditions occur. Device according to one of the preceding claims, characterized in that a further range for the actual value is defined, which he all It is possible to include values and an error is detected when an actual value outside this range occurs. Device according to one of claims 1 to 3, characterized that the Sensor is an inductive exhaust gas feedback indicator is.