JPH0346055B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a displacement detection device that detects mechanical displacement of an object or liquid surface using magnetostriction, and in particular for long-distance transmission of electrical signals corresponding to mechanical displacement. It concerns a device suitable for the case.

Conventional technology and its problems Conventionally, as a displacement detection device for detecting mechanical displacement of an object or liquid surface using magnetostriction phenomenon, for example, Japanese Patent Application Laid-Open No. 1986-
The one described in Publication No. 66710 is known. That is,
A current pulse is passed through the magnetostrictive wire, and an ultrasonic wave (torsional strain) is generated by the so-called Wiedemann effect in a part of the magnetostrictive wire adjacent to a permanent magnet that can move along the magnetostrictive wire, and the magnetostrictive wire is moved to a specific part of the magnetostrictive wire. By measuring the propagation time of ultrasonic waves,
It detects mechanical displacement applied to a permanent magnet.

In the case of this type of device, the transmitter consists of a magnetostrictive wire, a permanent magnet, and a strain detector that detects ultrasonic waves propagating on the magnetostrictive wire. The receiving section, such as the circuit that amplifies the voltage signal caused by the ultrasonic waves detected by the detector and the circuit that calculates the mechanical displacement given to the permanent magnet based on the arrival time of this voltage signal, should be installed at a location away from the transmitting section. is customary. Therefore, a cable for supplying current pulses from the pulse generating circuit to the magnetostrictive wire and a cable for sending voltage signals from the strain detector to the receiving section are wired between the transmitting section and the receiving section. There must be.

However, when the above displacement detection device is applied to liquid level detection in tankers, etc., or when data is centrally managed in one place such as in a plant factory or steel equipment, the transmitter and receiver must be separated far apart. Therefore, there is a problem that the cable connecting the two becomes long, and the voltage signal sent from the distortion detector is attenuated and becomes undetectable.
The reason for this is that the output signal sent from the strain detector has a high frequency component due to ultrasonic waves, and since this signal is transmitted as a voltage signal within the cable, it is attenuated by the stray capacitance of the cable itself. be.

Also, when a current pulse is passed through one cable, this current pulse may have an adverse effect on the other cable or other circuits, so shielded wire must be used as the cable, and such shielding There was also a problem in that wiring costs increased when multiple lines were installed over long distances.

OBJECT OF THE INVENTION The present invention has been made in view of such conventional problems, and its purpose is to transmit signals based on mechanical displacement of permanent magnets even if the transmitter and receiver are located far apart. An object of the present invention is to provide a displacement detection device that can transmit data accurately and reduce wiring costs.

Structure of the Invention In order to achieve the above object, the present invention includes a rectangular wave generation circuit that generates a rectangular wave A with a constant period, and a rectangular wave generation circuit that generates a rectangular wave A with a constant period in a transmitting section disposed near the magnetostrictive wire.
a pulse generation circuit that supplies a current pulse C to the magnetostrictive wire that rises at the same time as the rising of A substantially rectangular wave bias signal E that rises simultaneously with the voltage signal D and has the same period as the rectangular wave A.
a superimposition circuit that superimposes the superimposed voltage signal F into a current signal i, an output transistor that converts this superimposed voltage signal F _into a current signal i, and a constant voltage circuit that consumes a constant current _i and supplies a constant voltage to operate each circuit of the transmitter. is provided between the above-mentioned transmitting section and a receiving section located at a location away from the transmitting section, and at the same time the receiving section supplies the consumption current _IC to the constant voltage circuit, and at the same time, current is supplied from the output transistor to the receiving section. The wiring that transmits the signal i _s is connected, and the receiver is supplied with a constant power supply voltage V _c , and a circuit that erases the consumed current i _c from the signal flowing through the wiring, and the remaining signal H
A circuit for obtaining a signal proportional to the time t taken for the ultrasonic waves generated at the part of the permanent magnet to reach the strain detector is provided.

Effect of the Invention In the receiving section, a voltage waveform D due to ultrasonic waves generated near a permanent magnet by passing a current pulse C through a magnetostrictive wire, and a substantially rectangular waveform bias signal E having a constant period that rises at the same time as the current pulse C. are superimposed. The reason why the bias signal E is superimposed on the originally necessary signal waveform D is that if the bias signal E is set at the rising edge and reset at the falling edge, the set signal, the reset signal, and the originally necessary ultrasonic wave can be combined into one waveform. This is because it becomes possible to carry three signals, which facilitates signal processing in the receiving section. In general, displacement detection does not end with only one waveform, but is repeated many times, so if an ultrasonic signal is added to a signal that does not have a set signal or reset signal, noise due to current pulses will occur. It becomes difficult to distinguish between the signal and the ultrasonic signal. On the other hand, when the above-mentioned superimposed signals are used, signal discrimination is greatly simplified. The above-mentioned superimposed signal F is converted into a current signal i _s by the output transistor and transmitted through the wiring. Since the current signal i _s is not attenuated by the stray capacitance of the wiring, a clear signal can be received at the receiver.

On the other hand, the constant voltage circuit of the transmitting section supplies a constant voltage to each circuit of the transmitting section (first function), for example, also supplies a constant voltage to the pulse generating circuit. Although the current consumption of the pulse generation circuit fluctuates greatly, the second function of the constant voltage circuit is to prevent other circuits from being adversely affected by this current consumption.

The sum G of the consumption current i _c and the current signal i _s flows through the wiring. In the receiving section, the consumed current i _c is erased from these currents i _c + i _s , and the necessary signal from the remaining current signal i _s , that is, the time it takes for the ultrasonic waves generated at the permanent magnet part to reach the strain detector. Obtain a signal proportional to t. When erasing the consumption current i _c from the current i _c +i _s flowing through the wiring, if the consumption current i _c fluctuates, it is difficult to extract only the original signal current i _s . Therefore, the constant voltage circuit makes the current consumption i _c of the transmitter constant, making it easy to extract only the signal current i _s from the current i _c +i _s flowing through the wiring. This is the third function of the constant current circuit.

As mentioned above, the wiring serves both for supplying current consumption and for signal transmission, so if you connect the transmitter and receiver with at least one pair of wires (one signal wire and one ground wire), Enough. Therefore, even if the transmitting section and the receiving section are provided at separate locations, the wiring cost is low and displacement can be detected accurately.

DESCRIPTION OF EMBODIMENTS FIG. 1 shows the external appearance of a displacement detection device according to the present invention;
FIG. 2 shows its internal configuration, and FIG. 3 shows signal waveforms at various parts of the electric circuit shown in FIG.

In Figure 1, 1 is a probe with a built-in magnetostrictive wire 2;
3 is a permanent magnet, 4 is a probe head, and a transmitter shown in FIG. 2 is built into the probe head 4. A coaxial cable (or single-core shielded wire) 53 connects the probe head 4 and a receiving section located far away.

In the receiving section I, a rectangular wave generating circuit 5, a differentiating circuit, and transistors 8 and 11 constitute a pulse generating circuit, and an oscillating circuit 5 generates a rectangular wave as shown in FIG. 3A. The rectangular wave is differentiated by a differentiator circuit consisting of 7,
The base voltage of transistor 8 is as shown in FIG. 3B. Since a constant voltage V ₀ is supplied to the collector of the transistor 8 via the resistor 9, the differential waveform shown in FIG. 3B is shaped and the collector voltage of the transistor 8 changes as shown in FIG. The voltage waveform of C is a PNP transistor 11 whose emitter is supplied with a constant voltage V ₀ through a resistor 10.
Therefore, when a pulse like that shown in FIG.

When a current pulse is applied to the magnetostrictive wire 2, torsional strain (ultrasonic waves) is generated at the permanent magnet 3, and the arrival of the strain is detected by the strain detector 14. Distortion detector 14
There are methods to use piezoelectric elements and methods to apply the inverse magnetostriction phenomenon to convert the detected strain into an electrical signal, but in either case, the signal is transmitted to the subsequent circuit via the conductors 15 and 16. Ru.

The signal detected by the distortion detector 14 is applied via a capacitor 20 to an inverting type first-stage amplification section composed of a single-power supply operation type 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. . Further, a bias voltage divided by resistors 21 and 22 is applied to the positive input terminal of the operational amplifier 17.

An example of the signal amplified by the operational amplifier 17 is shown in FIG. 3D. In the figure, 23 is a signal due to amplified torsional strain, and 24 is high-frequency noise generated because a current pulse having the shape shown in FIG. 3C is supplied to the magnetostrictive wire 2. The high frequency noise 24 is detected by the distortion detector 1
4 must be installed near the magnetostrictive wire 2, and the influence of the flow of current pulses appears on other circuits, such as the operational amplifier 17. This will appear as an unnecessary waveform like this.

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 2 or while the unnecessary waveform continues. In this embodiment, a first-order delay element is used as the simplest delay circuit. That is, the square wave generation circuit 5
The output of transistor 2 is supplied via a resistor 25 to the collector of which a constant voltage V ₀ is supplied via a resistor 27.
Applied to the base of 6. Therefore, the voltage waveform at the collector of the transistor 26 becomes the inverted waveform of FIG.
is as shown in Figure 3E.

The above voltage waveform E is inputted to the negative input terminal of a single power supply operation type operational amplifier 31 via a resistor 30, and the output of the operational amplifier 17 is also inputted to this negative input terminal via a capacitor 32 and a resistor 33. ,
The waveforms D and E in FIG. 3 are superimposed and input to the operational amplifier 31. In addition, operational amplifier 3
A bias voltage divided by resistors 34 and 35 is applied to the positive input terminal of No. 1.

The output of the operational amplifier 31 is applied via a resistor 36 to the base of an output transistor 37, and the emitter of this output transistor 37 is grounded via a resistor 38. And the emitter voltage is resistor 3
9 to the negative input terminal of the operational amplifier 31, the output transistor 37
The emitter voltage of Figure 3D and E is as shown in Figure 3F.
The waveforms are superimposed and inverted. In other words, the unnecessary voltage waveform (24 in FIG. 3D) due to high-frequency noise is pushed to a lower level than the originally necessary waveform 41 like the waveform 40 in FIG. 3F, so that unnecessary signals can be distinguished. become.

The fact that the emitter voltage becomes as shown in Figure 3 F means that the current flowing through the resistor 38 between the emitter and ground, that is, the current waveform i _s flowing from the collector of the output transistor 37 to the emitter, will also have a waveform similar to F. As a result, the voltage signal of the operational amplifier 31 is converted into a current signal by the output transistor 37.

The constant voltage circuit is a circuit that supplies constant voltages v ₀ and v ₁ for operating the oscillation circuit 5, transistors 8 and 11, and two operational amplifiers 17 and 31, and includes three voltage regulators 42 to 44 and resistance 4
5 to 47, and a filter including capacitors 48 to 52. With this constant voltage circuit,
Current consumed by transistors such as operational amplifiers i _c
is kept constant, and other circuits are prevented from being affected by the pulse current from the transistor 11.

Coaxial cable 53 connecting the transmitter and receiver
Since one end is connected to the collector of the output transistor 37 and the constant voltage circuit, the current flowing through the coaxial cable 53 is i _c +i _s , and the current waveform is the signal waveform i _s as shown in FIG. 3G. Current consumption
The shape is a superimposition of i and _c .

In the receiving section, a constant power supply voltage V _c is applied to the resistor 54.
It is connected to a coaxial cable 53 via. Since the current shown in FIG. 3G is flowing through the coaxial cable 53, both ends of the resistor 54 are connected to a differential amplifier 55, and the output of the differential amplifier 55 is connected to the operational amplifier 5.
By erasing only the amount corresponding to the consumed current i _c by 6, it is possible to obtain only the necessary signal waveform i _s as shown in FIG. 3H.

Similarly to the waveform of F, FIG. 3H has a waveform in which the detection signal D and the bias signal E are superimposed. Therefore,
The mechanical displacement applied to the permanent magnet 3 can be determined by setting it at the rising edge of the waveform H and measuring the time t from this setting time until the ultrasonic signal arrives. If the time measurement is terminated at the falling edge of the waveform H, that is, by the set signal, the ultrasonic signal and the noise signal can be easily distinguished, and the measurement of the time t becomes extremely simple. In addition,
The reason why the ultrasonic signal, set, and reset signals are obtained from the signal _current Is after eliminating the consumption current _Ic from _the total current _Ic + Is is because the consumption current _Ic is the signal current.
This is because it is difficult to extract necessary signals such as ultrasonic signals directly from the total current i _c +i _s because it is larger than the value of i _s . As a method of converting this time t into an electrical signal proportional to the mechanical displacement, for example, start a clock at the rise of the waveform shown in Figure 3H, and set the clock when the ultrasonic signal arrives, as a digital signal. can be detected, and the third
By starting a voltage that changes in a sawtooth waveform with the rise of the waveform shown in Figure H, and sampling and holding the voltage value of the sawtooth wave at that moment when the ultrasonic signal arrives, it can be detected as an analog signal.
In any case, the time t can be easily converted into an electrical signal using conventional techniques.

In the above embodiment, in order to eliminate the influence of high-frequency noise caused by the current pulse, a first-order delay element, which is a delay circuit, is provided in the transmitting section, and a bias signal that operates with a delay at the time when the current pulse is applied to the magnetostrictive wire is generated. (Fig. 3E) is superimposed on the ultrasonic signal (Fig. 3D) detected by the distortion detector 14 to distinguish unnecessary signals due to high frequency noise. Of course, it may be provided not only in the transmitter but also in the receiver.

Effects of the Invention As is clear from the above explanation, according to the present invention, since a pulse generation circuit is provided in the transmitting section, there is no need for wiring for passing current pulses between the transmitting section and the receiving section, which reduces wiring costs. can be reduced.

In addition, the output transistor converts the voltage signal of the distortion detector into a current signal, and this current signal is transmitted to the receiver via the wiring, so the signal is not attenuated by stray capacitance in the wiring, and the signal is Effective for long-distance transmission.

In addition, since the necessary detection signals are superimposed on the power supply wiring to the constant voltage circuit and transmitted, inexpensive wiring such as coaxial cables and single-core shielded wires can be used, and wiring can be done over long distances. Wiring costs can be reduced even over a long period of time.

Furthermore, since a constant voltage circuit is provided in the transmitter to always supply a constant voltage to each circuit in the transmitter, it is possible to eliminate adverse effects such as disturbances in the power supply caused by current pulses. Since the constant voltage circuit makes its current consumption constant, even if the consumption current and the signal current are sent through the same wiring, only the signal current can be easily extracted at the receiving section.

Furthermore, in the present invention, since a substantially rectangular wave bias signal is superimposed on the ultrasonic signal detected by the distortion detector, three signals, the set signal, reset signal, and ultrasonic signal, can be superimposed on one waveform. This has the advantage that the propagation time of ultrasonic waves can be easily measured using a simple circuit in the receiving section.

[Brief explanation of drawings]

FIG. 1 is an external view of a displacement detection device according to the present invention, FIG. 2 is an internal configuration diagram of the displacement detection device, and FIG. 3 is a signal waveform diagram of various parts of the electric circuit shown in FIG. 2... Magnetostrictive wire, 3... Permanent magnet, 5... Rectangular wave generation circuit, 14... Strain detector, 17, 31... Operational amplifier, 37... Output transistor, 42-4
4... Voltage regulator, 45-47... Resistor,
48-52... Capacitor, 53... Coaxial cable (wiring),... Transmitting section,... Constant voltage circuit,
...Receiving section.

Claims (1)

[Claims] 1. Propagation of ultrasonic waves to a specific part of the magnetostrictive wire by passing a current pulse through the magnetostrictive wire to generate an ultrasonic wave at a portion of the magnetostrictive wire adjacent to a permanent magnet that is movable along the magnetostrictive wire. In a device that detects mechanical displacement applied to a permanent magnet by measuring time, a transmitter I placed near the magnetostrictive wire includes a rectangular wave generating circuit 5 that generates a rectangular wave A with a constant period. ,
A pulse generation circuit that supplies a current pulse C that rises simultaneously with the rising of this rectangular wave A to the magnetostrictive wire, a strain detector 14 that is provided at a specific location on the magnetostrictive wire and detects the ultrasonic wave that propagated on the magnetostrictive wire, and a strain detector 14 that detects ultrasonic waves propagated on the magnetostrictive wire. The above rectangular wave A is added to the voltage signal D detected by the device 14.
a superimposition circuit that superimposes a substantially rectangular wave bias signal E that rises at the same time and has the same period as the rectangular wave A;
An output transistor 37 that converts this superimposed voltage signal F into a current signal i _s and a constant voltage circuit that consumes a constant current i _c and supplies a constant voltage for operating each circuit of the transmitter I are provided. Between the above-mentioned transmitting section and a receiving section disposed at a location away from the transmitting section, the receiving section supplies a current consumption i _c to the constant voltage circuit, and at the same time a current signal i _s is sent from the output transistor 37 to the receiving section. A transmission wiring 53 is connected, and a constant power supply voltage V _c is supplied to the receiving section.
A circuit 55 eliminates the consumption current i _c from the signal flowing through the wiring 53, and a signal proportional to the time t taken for the ultrasonic waves generated at the permanent magnet part to reach the strain detector from the remaining signal H. What is claimed is: 1. A displacement detection device, comprising: a circuit for obtaining a displacement. 2. The displacement detection device according to claim 1, wherein the constant voltage circuit includes a voltage regulator and a filter including a resistor and a capacitor. 3. Claim 1, wherein the above-mentioned wiring is a coaxial cable or a single-core shielded wire.
2. Displacement detection device according to item 1 or 2.