JPH06213673A - Fault detector circuit device - Google Patents

Abstract

PURPOSE: To surely detect an obstruction such as short circuit, disconnection or the like by regularly detecting the obstruction when a processed signal reaches one of two upper and lower areas. CONSTITUTION: The output side of an amplifier 15 has resistors 24, 25 through a resistor 23, and is connected to a potential divider connected between a feed voltage and an earth. The common connecting point of the three variable resistors 23, 24, 25 is also connected to the output side A. Positive exciting area is clearly limited in order to generate an upper limit signal area, and an arithmetic amplifier with open collector is operated through the variable resistance circuits 23, 24, 25. The potential divider formed from the resistors 23, 24 is useful as the upper limit stopper setting function element under the open collector state with no current. The lower signal limit is realized by the resistors 23, 24 and the resistor 25. This combination of the resistors is useful as the lower limit stopper setting function element in the maximum collector current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The invention starts from a fault detection circuit arrangement for the evaluation of sensor signals, which comprises a sensor whose output signal is processed and an evaluation device to which the processed signal is supplied. There is.

[0002]

It is known to measure a physical quantity, for example pressure, by means of a resistance whose resistance value changes on the basis of the action of pressure. These resistors are then usually connected as a bridge circuit between the supply voltage and ground. When pressure acts on at least one of these resistors, the bridge voltage changes, which is taken out and amplified to a value that can be evaluated in the amplifier circuit which is connected downstream. The output signal of the amplifier circuit is therefore directly pressure-dependent.

Such a pressure measuring device is known from West German patent application No. 4122434. In this known device, further measures are taken to protect the sensor in the event of an overvoltage on the supply line or in the case of a misconnection.

However, it is not publicly known to perform appropriate fault detection for surely detecting a fault that may occur.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a circuit device capable of reliably detecting a fault such as a short circuit or a disconnection.

[0006]

According to the invention, the object is to set an upper region and a lower region, and the sensor signal electrically reaches the two regions in a fault-free state. This is solved by providing a limit on the gain and in the evaluation circuit a fault is detected whenever the processed signal reaches one of the two regions.

[0007]

The fault detection circuit arrangement according to the invention for the evaluation of sensor signals has the advantage over the circuit arrangements known from the prior art that reliable fault detection is possible and is of this type. A fault is a concept that includes a short circuit and a disconnection of a line that guides a signal.

This advantage is due to the fact that the sensor signal is
An area which is limited to a predetermined area that cannot be separated even in the case of signal overcontrol, and an area which continues to the upper side and the lower side of this area or an area further apart from this area is used as an area for detecting an error. It is realized by A fault is then detected when the output signal occurs in one of the fault zones.

It is particularly advantageous if the circuit is constructed such that the output signal of the sensor decreases as the physical quantity to be measured increases. Therefore, it is possible to form a circuit-formed electric stopper setting functional element which cannot be lowered only by given existing conditions for the purpose of limiting the lower fault region without additional cost. it can. Short overcontrols do not cause false fault response.

With the occurrence of a suitable offset, the signal characteristic curve, which is inversely proportional to the physical input quantity, is shifted so that the area formed by the offset can be used as a fault detection area.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings with reference to the accompanying drawings.

In the embodiment shown in FIG. 1, the sensor element is shown at 10, which is, for example, a Hall element used for magnetic field pickup. The sensor element 10 is inserted between the power supply voltage UV and the amplifier 11, and the output voltage of the amplifier 11 is connected to the inverting input side of the resistor 12 and the Zener diode 13.
And a variable resistor 14 arranged in parallel therewith and adjusted in series, and the intermediate tap of the variable resistor is connected to the non-inverting input side.

The output signal of the sensor element 10 is supplied to an amplifier 16 via two temperature-dependent resistors 14 and 15. The amplifier 16 is connected to the power supply voltage UV via a diode 17, and a capacitor 18 is provided between its output side and its inverting input side. The non-inverting input side is led to the ground via the capacitor 19, and the capacitor 2 is connected between the inverting input side of the amplifier 16 and the ground.
0 is provided.

The variable resistor 21 is provided between the power supply voltage UV and the ground. The middle tap is the amplifier 16
Output A which is connected to the inverting input of the and which can take out the output signal UA via another variable resistor 22
It is connected to the.

The output of the amplifier 16 is connected via a resistor 23 to a voltage divider having resistors 24 and 25 and connected between the supply voltage and ground. At that time, the common connection point of the three variable resistors 23, 24 and 25 is also connected to the output side A.

A capacitor 26 is provided between the power supply voltage and ground.
Is provided, and another capacitor 27
It is provided between the z-ground. Another capacitor 28
Is provided between the signal output side A and the Fz ground, and the capacitor 29 is provided between the EL ground and the terminal Fz ground.

Another embodiment of the present invention is shown in FIG. At that time, for example, the sensor element 10, which is a pressure sensor,
Resistors 30, 31, 32 configured as bridges,
33, the feed diagonals of which are connected to the feed voltage UV via a temperature-dependent resistor 34,
On the other hand, the other side of the feeding diagonal point is connected to the ground.

The resistance of at least one, and preferably all of the resistors 31 to 34, depends on the measured quantity, that is to say the pressure to be sensed in this case, and the output voltage of the sensor element 10 is Uan. Has been done.

The other diagonal of the bridge device is connected via resistor 35 to the non-inverting input of operational amplifier 36 and via resistor 37 to the inverting input of operational amplifier 37. The operational amplifier 36 is connected via its power supply terminal and the resistor 38 to the power supply voltage UV, which is further connected to ground.

The output side of the operational amplifier 36 is connected to the inverting input side via the resistor 38 and the capacitor 39. Further, a parallel circuit of the capacitor 40 and the two resistors 41 and 42 is provided between the inverting input side and the ground.

Power supply voltage UV, ground and operational amplifier 3
A resistor 38 is provided between the power supply terminal 6 and a power supply terminal 6, and a Zener diode 43 is provided in series with this resistor, and a capacitor 44 is connected in parallel to this Zener diode.

The output side of the operational amplifier 36 is connected through a resistor 45 to a current mirror composed of transistors 46 and 47. Current mirror transistor 4
The emitter of 6 is connected to ground via a resistor 48, the emitter of the transistor 47 of the current mirror is connected to ground via a resistor 49, and the collector of the transistor 47 is connected to the signal output side A, Resistance 50
Is connected to the power supply voltage UV via.

A collector 51 is provided in parallel with the resistor 50. Resistors 52 and 53 are further provided on the connection line between the output side A and the resistor 50 and the collector of the transistor 47. These resistors are connected to the non-inverting input side of the operational amplifier 36 as a series circuit. The capacitor 54 is provided between the output side A and the ground GND. A capacitor 55 is provided between GND and ground.

The evaluation circuit belonging to the sensor preferably consists of only one hybrid. The hybrid power supply connection terminal V, output terminal A, and ground connection terminal GND are connected to a control device 56 in a vehicle, for example, via a cable or a cable bundle. At that time, the power supply connection terminal and the output side A
A pull-up resistor 57 is provided between the terminal and a terminal connectable to the. The terminal connectable to the output side is the AD converter 58.
Have been led to. The digital output signal of the AD converter is subsequently evaluated as a sensor output signal in a control unit or other evaluation unit.

With two circuit arrangements, it is possible to carry out fault detection in the analog output signal Uan by forming two electrical voltage ranges which cannot be realized by signal overcontrol. Therefore, it is possible to detect both possible faults in the cable bundle and faults in the sensor itself.

In the characteristic curve which is proportional to the physical input quantity, for example by forming an offset of 0.5 V,
A region I is formed which lies between 0 and 0.5 V and cannot be realized by a signal. This area can be used as a failure detection area on the lower side.

A second such fault detection area II lies, for example, between 4.5 and 5V. This region is realized by limiting the electrically converted physical region to 4.5V, the upper limit of which is determined by the supply voltage.

These two regions are shown in FIG. 3a, in which the output voltage with respect to the quantity to be measured, eg the pressure p, is shown.

The circuit arrangement of FIG. 1 clearly limits the positive excursion region for the production of the upper limit signal region. An operational amplifier with an open collector is then activated via the variable resistance network 23.24 and 25. Resistance 23
The voltage divider formed from 24 and 24 serves as an upper limit stop setting element under currentless, open collector conditions. The lower signal limit is the voltage divider 23 and 24.
And by resistor 25. This resistance combination serves as a lower limit stopper setting functional element at the maximum collector current.

As a characteristic curve, it can be seen that the distributions shown in FIG. 3a or 3b occur, with which the output voltage for the measured quantity, ie pressure or acceleration or the like, rises together. Regions II and I are formed above and below the characteristic curve in which the characteristic curve is not allowed to occur.

Therefore, when the regions I and II are determined as shown in FIG. 3b, a distance is provided between the local maximum of the measurement region and the fault region, so that the fault detection region is For example between 0V and 0.3V and 4,7 and 5.0V, an even more reliable fault detection is realized.

Fault detection is possible by comparison of the sensor voltage with the upper and lower limit values, where the fault detection is triggered above the upper limit value and below the lower limit value. This overshoot or underrun can also be caused by a wire break, short circuit, or the like. The comparison is performed in the evaluation device, for example, in the control device after AD conversion.
The fault can be stored in the instruction or fault memory.

The inverted characteristic curve shown in FIG. 3c has the additional advantage brought about, in particular, in the lower signal region by the restrictions acting on its own. Due to this limitation, neither short-time overcontrols, eg short pressure peaks in the pressure sensor, lead to a signal reaching the fault detection area and thus false fault detection.

The circuit arrangement which makes it possible to realize such an inverted characteristic curve, ie the signal is inversely proportional to the input quantity and has a high offset, is the circuit arrangement of FIG. At this time, the lower limit is set by selecting an appropriate resistance value.

More specifically, in the circuit of FIG. 2, a bridge circuit consisting of four resistors is actively unbalanced so that the resistance value on one side increases and the resistance value on the other side decreases depending on the measured quantity. become.

If the bridge circuit becomes unbalanced, with resistors 30 and 33 increasing and resistors 31 increasing and 32 decreasing, additionally the offset must be replaced from the lower end of the power control region to the upper end. I won't. In that case, the output signal is at the upper value determined by the offset when there is no input quantity, and when the signal is added,
The output voltage decreases until it reaches a lower threshold defined by the resistor in parallel with resistor 50 and pull-up resistor 57 and resistor 49 when the measurand is higher.

The adjustment of the offset is performed by the amplifier 11 and the resistor 14.

[Brief description of drawings]

FIG. 1 is a circuit schematic diagram of a first circuit of the present invention.

FIG. 2 is a schematic diagram of a similar circuit as is known from the West German patent application mentioned at the outset, but expanded by the features of the invention.

FIG. 3 is a diagram showing the corresponding signal course and fault detection area.

[Explanation of symbols]

 10 sensor elements

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Klaus Mickley Germany Ludwigsburg Hospital Strasse 42

Claims (7)

[Claims] 1. An upper region and a lower region in a fault detection circuit device for evaluating a sensor signal, which comprises a sensor whose output signal is processed and an evaluation device to which the processed signal is supplied. Is set, and the sensor signal is electrically restricted so that it cannot reach the two regions in the undisturbed state, and in the evaluation circuit the processed signal reaches one of the two regions. A fault detection circuit device characterized in that a fault is always detected when a failure occurs. 2. The evaluation device is a control device to which the processed signal is supplied via an AD converter.
The fault detection circuit device described. 3. The sensor is a bridge circuit consisting of pressure-dependent resistors, and the pressure increase increases the resistance of two resistors and reduces the resistance of two other resistors. Alternatively, the fault detection circuit device according to item 2. 4. The fault detection circuit device according to claim 1, wherein an acceleration sensor is used as the sensor. 5. At least one operational amplifier with an open collector is provided, said operational amplifier serving as an upper stopper under currentless, open collector operating conditions and having a maximum collector current. 2. A resistor circuit network which plays a role of a lower stopper in FIG.
5. The fault detection circuit device according to any one of 1 to 4. 6. The output signal is at an upper value determined by the offset when there is no input quantity and when the signal is applied, the output signal is reduced to the extent that it is limited by the resistor combination in the subsequent rise of the signal. The fault detection circuit device according to any one of claims 1 to 5, wherein a circuit constant is defined so that 7. The fault detection circuit arrangement according to claim 6, wherein the resistor combination consists of two adjustable resistors and a pull-up resistor, these resistors forming the lower threshold of the output signal.