JPS61245019A - Displacement detecting device - Google Patents

Abstract

PURPOSE:To eliminate an unnecessary signal waveform generated by a high frequency noise, by delaying a function of a circuit, while a current pulse is being supplied to a magnetostrictive line, or only when an unnecessary waveform is continued. CONSTITUTION:An ultrasonic wave is generated in a part of a magnetostrictive line 1 to which a permanent magnet 2 which can move along the magnetostrictive line stands close, a propagation time of the ultrasonic wave to a specified part of the magnetostrictive line 1 is measured, and a mechanical displacement given to the permanent magnet 2 is detected. Also, a first-order lag element III is provided as a delaying circuit for generating a bias signal which is operated with a delay at the time when a current pulse is impressed to the magnetostrictive line 1, this signal is superposed on a voltage signal by the ultrasonic wave which is detected in the specified part, and also a Schmitt trigger circuit V and a differentiating circuit VI are provided as a pulse forming circuit which is operated by the potential corresponding to an ultrasonic signal in the superposed voltage signal and generates a pulsative signal, and a sample holding circuit 45 is provided as a detecting circuit for obtaining an electric signal being proportional to a mechanical displacement given to the permanent magnet 2 by this pulse signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a displacement detection device that detects mechanical displacement of an object or liquid level using magnetostriction, and particularly to an electric device that can obtain the mechanical displacement as an electrical signal. It is related to circuits.

BACKGROUND OF THE INVENTION Conventionally, there has been known a displacement detection device that detects mechanical displacement of an object or a liquid surface by using magnetostrictive phenomena, such as that described in Japanese Patent Application Laid-open No. 55-66710.

That is, a current pulse is passed through the magnetostrictive wire, and an ultrasonic wave (torsional strain) is generated in the vicinity of the magnetostrictive wire by a permanent magnet that is movable along the magnetostrictive wire due to the so-called Wiedemann effect. Mechanical displacement applied to a permanent magnet is detected by measuring the propagation time of ultrasonic waves to a receiving section provided at a specific location.

However, in the case of this type of device, high-frequency noise is generated when supplying current pulses to the magnetostrictive wire, and this high-frequency noise requires that the receiver be installed near the magnetostrictive wire, and that the current pulse is This causes a problem in that the power supply section is disturbed and its influence appears in other circuits, resulting in detection as an unnecessary signal waveform.

Purpose of the Invention The present invention has been made in view of such conventional problems.
The purpose is that while a current pulse is supplied to the magnetostrictive wire,
Another object of the present invention is to provide a displacement detection device that can remove unnecessary signal waveforms caused by high-frequency noise by delaying the function of the circuit only while the unnecessary waveforms persist.

Structure of the Invention In order to achieve the above object, the present invention provides a delay circuit that generates a bias signal that operates with a delay at the time when a current pulse is applied to the magnetostrictive wire, and transmits the bias signal to a specific portion of the magnetostrictive wire. A pulse shaping circuit is provided which generates a pulsed signal by superimposing it on the voltage signal caused by the ultrasonic wave detected by the ultrasonic wave, and operates at a potential corresponding to the ultrasonic signal in the superimposed voltage signal, and the pulse signal generates a permanent magnet. A detection circuit is provided to obtain an electrical signal proportional to the mechanical displacement applied to the sensor.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows the overall configuration of a displacement detection device according to the present invention, and FIG.
The figure shows voltage waveforms at various parts of the electric circuit of the displacement detection device.

In Figure 1, 1 is a magnetostrictive wire, 2 is a permanent magnet, and 3 is a permanent magnet 2
This is a distortion detection device that is a receiving unit that detects the arrival of loss distortion emitted at a location.

The square wave oscillation circuit 4 is the 21st! A rectangular wave as shown in IA is generated, and the rectangular wave is differentiated by a differentiating circuit T composed of a capacitor 5 and a resistor 6, and the base voltage of the transistor 7 becomes as shown in FIG. 2B.

Since a constant voltage Vo is supplied to the collector of the transistor 7 via the resistor 8, the differential waveform shown in FIG. 2B is shaped and the collector voltage of the transistor 7 changes as shown in FIG. 2C. This voltage waveform of C is a constant voltage V through the resistor 9. is applied to the base of the PNP transistor 10 whose emitter is supplied, so when a pulse like that shown in FIG. It flows through the magnetostrictive wire 1 and the conducting wire 12. The conductors 11 and 12 are surrounded by a shield 13 to minimize the influence of current pulses on other circuits.

When a current pulse is applied to the magnetostrictive wire 1, torsional strain (ultrasonic waves) is generated at a portion of the permanent magnet 2, and the arrival of the strain is detected by the strain detection device 3. As the strain detection device 3, there are methods that use a piezoelectric element and methods that apply the inverse magnetostriction phenomenon to convert the detected strain into an electrical signal, but in either method, the impedance of the strain detection device is high and a shield is required. It is transmitted to the subsequent circuit via conductors 15, 16 protected by 14.

The signal detected by the distortion detection device 3 is applied via a capacitor 20 to an inverting type first-stage amplifier section (2) consisting of an operational amplifier 17 and resistors 18 and 19. Since the detected signal is an ultrasonic wave caused by torsional distortion, it is passed through a capacitor 20 in order to amplify only the high frequency component thereof, but the capacitor 20 may be omitted if there is no concern about low frequency noise. .

An example of the signal amplified by the operational amplifier 17 is shown in the second figure. In the figure, 20 is a signal due to amplified torsional strain, and 21 is high-frequency noise generated because a current pulse having the shape shown in FIG. 2C is supplied to the magnetostrictive wire 1. As already mentioned,
Although shields 13 and 14 are used to minimize the influence of current pulses on other circuits, the strain detection device 3 must be installed near the magnetostrictive wire l, and the current pulses must flow. The power supply section is disturbed by this, and the influence appears in other circuits, for example, the operational amplifier 17, so that an unnecessary waveform such as 21 in the second diagram appears as a signal.

This unnecessary waveform can be removed by using a delay circuit to stop the function of the operational amplifier 17 only while the current pulse is being supplied to the magnetostrictive wire 1 or while the unnecessary waveform continues. 0 In this embodiment, a first-order delay element (2) is used as the simplest delay circuit. That is, the output of the rectangular wave oscillation circuit 4 is a constant voltage V via the resistor 22.

is supplied to the collector via a resistor 24
Applied to the base of 3. Therefore, the voltage waveform at the collector of the transistor 23 becomes the inverted waveform of A in FIG. It will look like E.

The voltage waveform E is supplied to the next stage amplification section (2), which is composed of an operational amplifier 28 and a resistor 29.30, through a resistor 27.
Further, the amplifying section (2) is biased at -v2 via a resistor 31. Since the output of the first stage amplifier H is transmitted via the capacitor 32, the output of the operational amplifier 28 is transmitted to the second stage amplifier H.
As shown in Figure F, the waveforms of the second diagram and E are superimposed and reversed. In other words, the original signal due to torsional distortion (20 in the second diagram) changes around the bias voltage v2, and the unnecessary voltage waveform (21 in the second diagram) is shifted to a lower position like waveform 33 in Figure 2F. This means that unnecessary signals can be distinguished.

The operational amplifier 34, resistors 35, 36, and diode 37 constitute a Schmitt trigger circuit (2), and a voltage V that determines the operating point of the Schmitt trigger circuit V is applied through a resistor 38. Assuming that a voltage as shown in FIG. 2F is applied as v3, a voltage waveform as shown in FIG. 2G is obtained, which turns off only when the voltage of the operational amplifier 28 becomes less than V,'.

■, ” can be arbitrarily selected by the combination of resistors 35 and 36. Generally, when a piezoelectric element is used as the strain detection device 3, the originally required first waveform 39 is distorted due to the influence of reflection inside the device. Subsequently, the second waveform 40 tends to be detected, but the Schmitt trigger circuit V ignores this unnecessary second waveform 40 and detects the originally necessary first waveform 39.
can only be detected.

The step-like waveform shown in FIG. Obtain the pulse waveform shown in .

The generation time of the pulse shown in FIG. 2H coincides with the time when the ultrasonic wave generated by the permanent magnet 2 reaches the strain detection device 3. This pulse is applied to a sample input 46 of a sample and hold circuit 45.

On the other hand, the operational amplifier 48. Resistance 49. Transistor 50 and capacitor 51 constitute an integrating circuit (2). A constant voltage V is applied to the positive input part of the operational amplifier 48, the output part is connected to the base of the transistor 50, and the emitter voltage of the transistor 50 is fed back to the negative input part of the operational amplifier 48. The emitter voltage of the transistor 50 becomes equal to V, and the voltage difference across the resistor 49 becomes V and -V4, which becomes constant. That is, if the resistance value of the resistor 49 is R, a current i flows into the capacitor 51 via the transistor 50, and the voltage of the capacitor 51 changes with time and has a voltage waveform with a constant slope. Further, since the capacitor 51 is connected to the collector of the transistor 52, and the base of the transistor 52 is connected to the collector of the transistor 23 mentioned above via the resistor 53,
Figure 2! 0 at the time the current pulse is applied as shown in
A voltage waveform with a constant slope starting from volts will be obtained.

Since the transistor 52 turns ON when the output voltage of the rectangular wave oscillation circuit 4, shown in FIG. When the next current pulse is applied, the voltage of the capacitor 51 rises again with a constant slope, and this operation is repeated thereafter.

The voltage waveform in FIG. 2 is transmitted to the input section 47 of the sample-and-hold circuit 45, and the voltage at I (VS in the example in the figure) when the 211iUH sample pulse is input is held in the sample-and-hold circuit 45. This becomes the output signal. That is, the output signal voltage 5 of the sample and hold circuit 45 is proportional to the position of the permanent magnet 2 on the magnetostrictive wire 1.

In the above embodiment, the Schmitt trigger circuit (■) and the differential circuit (■) were used as the pulse shaping circuit, but when a piezoelectric element is not used as the strain detection device 3, the 40 in FIG.
Since lingering waveforms such as
Alternatively, the pulse signal may be obtained by extracting only the pulse signal and differentiating it.

Further, as a method of obtaining an electric signal proportional to the mechanical displacement given to the permanent magnet, the above-mentioned sample and hold circuit 4
5, a triangular wave-shaped voltage is started by a current pulse, and instead of sampling and holding the voltage value at the time when the pulse shaping circuit generates a pulse signal, for example, a clock is started by a current pulse, and the pulse shaping circuit is The clock may be set at the moment the circuit generates the pulse signal. In this case, a digital signal proportional to the mechanical displacement of the permanent magnet can be obtained.

Effects of the Invention As is clear from the above explanation, according to the present invention, a bias signal that operates with a delay at the time when a current pulse is applied to a magnetostrictive wire is superimposed on a signal detected by a receiving section, and this superimposed signal Since only the ultrasonic signal within is taken out by the pulse shaping circuit, unnecessary signals caused by current pulses can be easily removed, and the circuit is simple, so it has the advantage of being able to be constructed at low cost.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram of a displacement detection device according to the present invention, and FIG. 2 is a voltage waveform diagram of each part of the electric circuit of the displacement detection device. DESCRIPTION OF SYMBOLS 1... Magnetostrictive wire, 2... Permanent magnet, 3... Strain detection device (receiving part), 4... Oscillation circuit, 45... Sample hold circuit, ■... Inverting type first stage amplifier section ,■・・・−
Next delay element (delay circuit), ■...Next stage amplification section, ■...
・Schmitt trigger circuit, ■... Differential circuit. Applicant Sankyo Boeki Co., Ltd. Agent Patent Attorney Hidetaka Tsutsui Figure 2

Claims (3)

[Claims] (1) A current pulse is passed through the magnetostrictive wire, an ultrasonic wave is generated at a portion of the magnetostrictive wire adjacent to a permanent magnet that can be moved along the magnetostrictive wire, and the propagation time of the ultrasonic wave to a specific portion of the magnetostrictive wire is measured. In a device for detecting mechanical displacement applied to a permanent magnet, a delay circuit is provided that generates a bias signal that operates with a delay at the time when the current pulse is applied to the magnetostrictive wire, and the bias signal is applied to the magnetostrictive wire. A pulse shaping circuit is provided which superimposes the voltage signal caused by the ultrasonic wave detected at a specific portion of the circuit and generates a pulse-like signal by operating at a potential corresponding to the ultrasonic signal within the superimposed voltage signal, and generates the pulse signal. 1. A displacement detection device comprising a detection circuit that obtains an electrical signal proportional to the mechanical displacement applied to a permanent magnet. (2) The above-mentioned pulse shaping circuit includes a Shemite trigger circuit that operates at a potential corresponding to the tip of the ultrasonic signal within the superimposed voltage signal, and a differentiation circuit that differentiates the trigger signal. The displacement detection device according to item 1. (3) The above detection circuit uses the pulse signal of the pulse shaping circuit as a sample signal, holds a voltage with a constant slope that starts at the same time as the current pulse is applied to the magnetostrictive wire, and calculates the mechanical displacement given to the permanent magnet. The displacement detection device according to claim 1 or 2, comprising a sample and hold circuit that obtains an electrical signal proportional to .