JPH05113446A - Ac-bridge type measuring apparatus which can detect abnormality - Google Patents

Abstract

PURPOSE:To ensure the detection of the abnormality of an oscillating circuit in an AC-bridge type measuring apparatus wherein the pulse signal from the oscillating circuit is supplied as the AC signal. CONSTITUTION:When an oscillating circuit is normally operated, a current is not supplied from a diode D1. Therefore, the voltage of 1-4V appears at an out put Vout in response to the output current of an operation amplifier OP3, i.e., the magnitude of acceleration. Meanwhile, when the oscillating circuit fails and the pulse signal is stopped, a DC signal appears at an input terminal SF1. The DC signal is cut OFF with a capacitor C1. Therefore, 2.7V, which is divided by voltage dividing resistors R9 and R10, is inputted to one input terminal of a comparator CP. As a result, the output potential of the comparator CP rises up, and a transistor Tr1 becomes the ON state. Thus, the output Vout becomes approximately 0V.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC bridge type measuring device capable of detecting an abnormality, and more particularly to an AC bridge type measuring device supplied with a pulse signal output from an oscillation circuit as an AC signal. The present invention relates to an AC bridge type measuring device capable of surely detecting a circuit abnormality.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting an acceleration, an imbalance of an AC bridge circuit based on a change in impedance of a detection coil due to a displacement of a core is measured to detect the displacement of the core, and based on the displacement amount. Methods of measuring acceleration are known. At this time, as the AC signal,
The pulse signal output from the oscillator circuit is used.

FIG. 2 is a schematic block diagram of a conventional AC bridge type measuring device.

The first and second detection coils 1 and 2 having the same shape and electromagnetic characteristics are connected in series, and the core 3 is inserted into the inner hole thereof. One ends of first and second fixed coils 4 and 5 having the same impedance are connected to one ends J1 and J2 of the first and second detection coils 1 and 2, respectively, and the other ends of the fixed coils 4 and 5 are connected to each other. Commonly connected to the power supply voltage E. It is also possible to use resistors instead of the fixed coils 4 and 5.

The other ends of the first and second detection coils are commonly connected and connected to the collector of the transistor Tr. A pulse signal output from an oscillation circuit (not shown) is supplied to the base of the transistor Tr, and the emitter is grounded. One ends J1 and J2 of the first and second detection coils 1 and 2 are input to the differential amplifier OP.

In such a structure, when the core is displaced in response to acceleration, the first and second detection coils 1 and 2 are
Each end J1 and J2 of the
Since -.DELTA.E1) and (E-.DELTA.E2) are generated, a voltage (.DELTA.E1-.DELTA.E2) corresponding to the acceleration is generated from the output terminal Vout of the differential amplifier OP.

However, in the AC bridge type measuring device having the above configuration, when the potential difference between the terminals J1 and J2 is zero,
There was a problem that it was not possible to determine whether this was due to zero core displacement or due to a broken wire in the bridge.

In order to solve such a problem, for example, in Japanese Patent Publication No. 59-31012, the terminal J is used.
A method has been proposed in which the potentials of 1 and J2 are added to perform rectification and smoothing, and when the rectified and smoothed potential exceeds an upper limit value or a lower limit value, a bridge abnormality is determined.

[0009]

However, in the above-mentioned prior art abnormality detection method, it has not been considered that the potential difference between the terminals J1 and J2 becomes zero even when the oscillation circuit is stopped.

That is, if the oscillation circuit is stopped for some reason, the output voltage Vout of the differential amplifier OP becomes zero, and this is because the core displacement is zero, or the oscillation circuit is There is a problem in that it cannot be determined whether the failure is due to the failure of the AC bridge circuit and it is not possible to detect a defect in the AC bridge circuit.

An object of the present invention is to solve the above-mentioned problems of the prior art and provide an AC bridge type measuring device capable of detecting an abnormality.

[0012]

In order to achieve the above object, in the present invention, a pair of detection coils whose impedance changes according to the displacement of the core are arranged on two sides of the bridge circuit, and one of the bridge circuits is provided. In the AC bridge type measuring device for supplying a pulse signal between the opposing connection points of, and detecting the displacement of the core by measuring the potential between the other opposing connection points, pulse supply means for supplying a pulse signal, It is characterized in that it comprises smoothing means for smoothing the potential of one of the other opposing connection points, and abnormality detection means for determining an abnormality when the smoothed potential reaches a predetermined level. is there.

[0013]

When an abnormality occurs in the pulse supply means and the supply of the pulse signal is stopped, the potential at the other opposing connection point becomes constant, so that the output signal from the smoothing means rises (or falls). The level is reached, and the occurrence of anomalies can be detected.

[0014]

1 is a block diagram of an AC bridge type measuring apparatus capable of detecting an abnormality, which is an embodiment of the present invention.

In the figure, the sensor signal input terminal SF
1 and SF2 have terminals J1 of the AC bridge, respectively.
, J2 are connected. The sensor signal input to the input terminal SF1 is input to one input terminal of the operational amplifier OP1 via the resistor R1 and to one input terminal of the comparator CP via the capacitor C1. The sensor signal input to the input terminal SF2 is the resistance R2.
It is input to one input terminal of the operational amplifier OP2 via. The operational amplifier OP1 constitutes a peak hold circuit together with the resistors R3, R5 and the capacitor C3, and its output signal is inputted to one input terminal of the operational amplifier OP3 via the resistor R7. Similarly, the operational amplifier OP2 constitutes a peak hold circuit together with the resistors R4, R6 and the capacitor C4, and its output signal is inputted to the other input terminal of the operational amplifier OP3 via the resistor R8. The output signal of the operational amplifier OP3 is input to the base of the transistor Tr1 via the resistor R14.

One of the input terminals of the comparator CP is pulled up by a voltage dividing resistor R9 and a voltage dividing resistor R10.
Has been pulled down by. The voltage divided by the voltage dividing resistors R11 and R12 is input to the other end of the comparator CP. The output signal of the comparator CP is smoothed by the smoothing circuit composed of the resistor R13 and the capacitor C2, and is input to the base of the transistor Tr1 via the diode D1. The collector of the transistor Tr1 is connected to the output terminal.

When the power supply voltage E is set to 5.0V,
The resistance values of the voltage dividing resistors R9 and R10 are set so that the connection point thereof is about 2.7V, and the resistance values of the voltage dividing resistors R11 and R12 are set to the connection point of about 2.5V. It is set.

In such a configuration, when the oscillator circuit is operating normally, the sensor signal input terminals SF1 and S1 are connected.
Signals S1 and S2 having waveforms as shown in FIG. 3A are input to F2 according to the acceleration. The signals S1 and S2 are peak-held by the peak-hold circuit, and the peak signals SP1 and SP2 are input to the operational amplifier OP3. The operational amplifier OP3 detects the difference between the peak signals SP1 and SP2 (SP1−
Transistor T with the current corresponding to SP2) as the base current
Output to r1.

Further, the signal S input to the input terminal SF1
1 is input to one input terminal of the comparator CP via the capacitor C1. 2.5V is always applied to the other input terminal of the comparator CP by the voltage dividing resistors R11 and R12. The output signal of the comparator CP is the resistance R
It is smoothed by a smoothing circuit consisting of 13 and the capacitor C2, and becomes a sawtooth wave as shown in FIG. 3 (b).
The resistance value of the resistor R13 and the capacitance of the capacitor C2 that form the smoothing circuit are set so that the peak value of the output signal of the comparator CP does not exceed 0.6V.

As a result, the output signal of the comparator CP is blocked by the diode D1 and the base current is not supplied from the diode D1 to the transistor Tr1. Therefore, a voltage of 1 to 4 V appears at the output Vout according to the output current of the operational amplifier OP3, that is, the magnitude of acceleration.

On the other hand, when the oscillator circuit fails and the pulse signal stops, a 5V DC signal appears at the input terminal SF1 as shown in FIG. 3 (c). Since the input of this DC signal to the comparator CP is cut off by the capacitor C1, 2.7V divided by the voltage dividing resistors R9 and R10 is input to one input terminal of the comparator CP.

The other input terminal of the comparator CP is
Since the voltage of 2.5V divided by the voltage dividing resistors R11 and R12 is input, as shown in FIG.
The output signal of the comparator CP gradually rises to 0.6V
Over. As a result, since the transistor Tr1 is turned on, the output Vout becomes almost 0V, and the abnormality can be detected.

In the above-mentioned embodiments, when the oscillation circuit stops, the output Vout falls below the lower limit value of the predetermined range (1 to 4V) and is fixed to the "L" level (0V). However, the present invention is not limited to this, and when the oscillation circuit stops, the output Vout may exceed the upper limit value of the predetermined range and be fixed to the "H" level (5V).

[0024]

As described above, according to the present invention, when an abnormality occurs in the oscillation circuit and the supply of the pulse signal is stopped,
Since a voltage below (or above) the predetermined voltage range appears in the output, it becomes possible to reliably detect an abnormality in the oscillation circuit.

[Brief description of drawings]

FIG. 1 is a block diagram of an AC bridge type measuring device including an abnormality detection unit according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a conventional AC bridge type measuring device.

FIG. 3 is a timing chart of the main part of FIG.

[Explanation of symbols]

1 ... 1st detection coil, 2 ... 2nd detection coil, 3 ... core, 4 ... 1st fixed coil, 5 ... 2nd fixed coil

Front Page Continuation (72) Inventor Takahiro Omoto 1-4-1 Chuo 1-4-1 Wako City, Saitama Stock Company Honda R & D Co., Ltd.

Claims (1)

[Claims] 1. A pair of detection coils, which have the same electromagnetic characteristics and whose impedance changes according to the displacement of a core inserted inside, are arranged on two sides of a bridge circuit, and between the opposing connection points of one of the bridge circuits. Supply a pulse signal,
In an AC bridge type measuring device for detecting the displacement of the core by measuring the potential between the other opposing connection points, a pulse supply means for supplying a pulse signal and the potential of one of the other opposing connection points An abnormality detecting means for determining that an abnormality has occurred in the pulse supplying means when the smoothed potential reaches a predetermined level. AC bridge type measuring device.