JPS61215902A - Eddy current sensor - Google Patents

Abstract

PURPOSE:To improve the responsiveness and the sensitivity for the permeability and the high frequency by providing a magnetic core, etc., composed of an operating side coil, a dummy side coil and the magnetic core composed of the amorphous magnetic alloy wire inserted into these both coils. CONSTITUTION:The sensor is composed of an operating side coil L1, a dummy side coil L2 and a magnetic core 9 consisting of a zero magnetic distortion amorphous magnetic alloy wire inserted into a coil L1 and a coil L2, an astable monostable multivibrator 11 to self-oscillate connected to the coils L1 and L2 and output corresponding to a distance X with the edge part near a body 12 to be measured and an edge part near the coil L1 of a iron core 9 and a smoothing circuit 10. The output of a vibrator 11 corresponding to the distance X with the body to be measured 12 is obtained. At such a case, the frequency is selected between 50kHz-200kHz and goes to be high sensitive. Next, the circuit 10 removes the alternating current part from the output and outputs the non-linear direct current part.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an eddy current sensor that is widely used for measurement and detection control of positioning, displacement, and speed.

[Conventional technology]

Conventionally, eddy current sensors such as those shown in FIGS. 5(a), (b), and (c) and FIG. 6 have been used.

This conventional eddy current sensor basically uses L-C or L
-Constructed by R's Brie and Ji circuits.

The sensor section 1a is composed of two air-core coils Lll and L12 on the dummy side and the active side.

This sensor section 1a includes a modulation circuit 2. It is connected to a meter (not shown) via a detection circuit 3, an amplification circuit 4, a correction circuit 5, and an amplification circuit 6.

On the other hand, the 1 oscillation circuit 3 is connected to the modulation circuit 2, and the power supply circuit 7
Power is supplied by

It has an amplifier circuit 4.6 for output and a correction circuit 5 for correcting output characteristics.

Conventionally, a coil in which Permalloy (trade name) or ferrite is inserted as a magnetic core has been used.

[Problem that the invention seeks to solve]

However, the eddy current sensor including the conventional air-core coils Lll and L12 described above enables high-frequency excitation, but has low sensitivity.

In addition, the diameter of the sensing part is large compared to the measurement range, and the diameter and curvature of the detection target are limited to a predetermined range as shown in Figures 7 and 8, making local measurement difficult. There are major restrictions on usage conditions.

Furthermore, since the single oscillation circuit 3 has a separate configuration of passive double type, the circuit configuration is complicated.

In addition, in sensors equipped with operational amplifiers that correct nonlinear output to linear output, the amplification characteristics must be corrected by manually adjusting the constants of the multiplier depending on the type of object being measured. Ta.

On the other hand, permalloy, which is a ferromagnetic material, has high magnetic permeability and sensitivity at low frequencies, but low magnetic permeability responsiveness to high frequencies.

Also, although ferrite has good responsiveness to high frequencies, *
The problem is that the magnetic property and sensitivity are low, and the characteristics change significantly due to temperature changes, requiring temperature compensation.

The present invention was proposed to solve the above-mentioned problems, and has good responsiveness and sensitivity to magnetic permeability and high frequencies, is stable against temperature changes, has few restrictions on usage conditions, and has a simple circuit configuration. The purpose of this invention is to provide a small and light eddy current sensor.

A second object of the present invention is to automatically correct the amplification characteristics of the operational amplifier in accordance with the type of object to be measured when the output is made linear by the operational amplifier.

[Means for solving problems]

As a result of intensive research, the present inventors have found that amorphous magnetic alloys have good magnetic permeability and good responsiveness and sensitivity to high frequencies.
We discovered that it is stable against temperature changes.

For this reason, we considered using an amorphous magnetic alloy as the magnetic core of an eddy current sensor.

Furthermore, we considered simplifying the circuit by making the oscillation circuit a self-exciting compound type using an astable multivibrator.

Furthermore, in the case where the output is made linear by an operational amplifier, we considered automatically correcting the amplification characteristics of the operational amplifier in accordance with the type of object to be measured.

The present invention has been established based on the above-mentioned findings, and a first aspect of the present invention is a magnetic core comprising an actuation side coil, a dummy side coil, and an amorphous magnetic alloy wire inserted into the actuation side coil and the dummy side coil. and # an astable multivibrator that is connected to the actuation side coil and the dummy side coil and self-oscillates and outputs an output corresponding to the distance between the object to be measured and the end of the magnetic core closer to the actuation side coil, and the astable multivibrator. The second invention includes a smoothing circuit that removes the alternating current from the output from the vibrator and outputs only the DC component. A magnetic core made of amorphous magnetic alloy wire, which is connected to the actuating coil and the dummy coil, self-oscillates and outputs an output corresponding to the distance between the object to be measured and the end of the magnetic core closer to the actuating coil. a stable multivibrator, a smoothing circuit that removes alternating current from the output of the astable multivibrator and outputs only a DC component, an operational amplifier that corrects the nonlinear output from the smoothing circuit to a linear output, and the operating side. A correction coil is wound around a coil and corrects the amplification characteristics of the operational amplifier in accordance with the type of the object to be measured.

[Effect]

Next, to explain the present invention in detail, since an amorphous magnetic alloy is used as the magnetic core, it has good magnetic permeability and high frequency response and sensitivity, and is stable against temperature changes.

Amorphous magnetic alloys have a thickness of 30 to 404 m and are called ribbons due to their formation process.

A wire with a diameter of 0.18 mm or less can be obtained. Therefore, a magnetic core with excellent high-frequency characteristics and high-speed response characteristics is constructed.

Furthermore, even when this is bundled and used as a magnetic core, the diameter is 1 mm.
A magnetic core with the following narrow outer diameter can be easily obtained.

In eddy current sensors, the diameter of the object to be measured is related to the outer diameter of the magnetic core and has nothing to do with the coil diameter. ! The measurement range is wide relative to the part diameter, and there are no major restrictions on usage conditions.

Furthermore, since the thin amorphous magnetic alloy has high magnetic permeability and high inductance, the number of coil turns can be reduced and the outer diameter of the coil can be reduced, making it possible to reduce the outer diameter of the sensor as well.
Make it smaller and lighter.

Due to this reduction in size and weight, the inertial force of the movable object to be measured or the magnetic core for the magnetic sensor is reduced during measurement, so the strength of the support frame may be reduced, and mechanical responsiveness is improved.

Furthermore, the component includes an astable multivibrator that is connected to the actuation side coil and the dummy side coil and self-oscillates, and outputs an output corresponding to the distance between the object to be measured and the end of the magnetic core closer to the actuation side coil. The circuit configuration is simplified and the size and weight are reduced.

In the second aspect of the present invention, the nonlinear output from the astable multivibrator is further converted into a linear output by an operational amplifier. It is fed back and its amplification characteristics are corrected manually.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments with reference to the drawings.

First, an embodiment of the first invention will be described with reference to FIG.

This embodiment includes an actuating coil Ll, a dummy coil L2, a magnetic core 9 made of a zero magnetostrictive amorphous magnetic alloy wire inserted into the actuating coil L1 and the dummy coil L2, and the actuating coil L1 and the dummy coil L2. An astable multivibrator 1 connected to the coil L2, which self-oscillates and outputs an output corresponding to the distance X between the object to be measured 12 and the end of the magnetic core 9 closer to the actuating coil Ll. 1 and a smoothing circuit 10.

Power supply +E is active side coil L1 and dummy side coil L2
are connected to each other.

The active coil LL is further connected to the terminal T1 of the smoothing circuit 10 via the collector and emitter of the transistor Tri.

On the other hand, the dummy coil L2 is connected to the terminal T2 of the smoothing circuit IO via the collector and emitter of the transistor Tr2.

Here, the transistors Trl and Tr2 perform a switching action.

A connection midpoint 21 between the coil LL and the collector of the transistor Trl is connected to the base of the transistor Tr2 via a parallel circuit of a capacitor C2 and a resistor R2.

On the other hand, a connection midpoint 22 between the coil L2 and the collector of the transistor Tr2 is connected to the base of the transistor Tri via a parallel circuit of a capacitor Ct and a resistor R1.

Here, the capacitor C1 and the resistor R1, and the capacitor C2 and the resistor R2 perform a commutation function.

Next, the transistor Trl and the smoothing circuit 10
The connection midpoint 23 of the terminal TI is grounded via a resistor R4, and is also connected to a sliding terminal of a variable resistor VR for zero point adjustment.

Similarly, the emitter of transistor Tr2 and the smoothing circuit lO
The connection midpoint 24 of the terminal T2 is grounded via the resistor R3, and is also connected to the sliding terminal of the variable resistor VR.

Furthermore, the transistor Tri's transistor Tri and the smoothing circuit 1
The connection midpoint 25 of the terminal Tl of 0 is connected via the variable resistor VR,
Emitter of transistor Tr2 and terminal T of smoothing circuit IO
It is connected to the connection midpoint 26 of No. 2.

The smoothing circuit 10 removes the AC component and outputs the DC component. Output terminals T3 and T4 are connected to a meter (not shown).

J: Capacitors C1, C2, resistors R1゜R2, R3 mentioned above
, R4, variable resistor VR and transistor Tr1. Tr
2 constitutes an astable multivibrator 11.

Next, to explain the operation of this embodiment, the object to be measured 1
Astable multivibrator 11 corresponding to distance #X with 2
The output is obtained.

In this case, the frequency is selected between 50 KHz and 200 KHz to provide high sensitivity.

Next, the smoothing circuit IO removes the alternating current component from this output and outputs a nonlinear DC component as shown in FIG.

Here, cases are shown in which the magnetic core 9 is composed of one, three, six, or eight zero magnetostrictive amorphous magnetic alloy wires.

The object to be measured 12 is a copper plate with a thickness of 2 mm.

Next, an embodiment of the second invention will be described.

First, the configuration of this embodiment will be explained with reference to FIG.
The sensor section 1, astable multi-ibrator 11, and smoothing circuit 10 in the embodiment shown in FIG. 1 have the same configuration.

The output terminal T4 of the smoothing circuit IG is connected to the non-inverting input terminal of the operational amplifier 13 via a resistor Rc.

On the other hand, the output terminal T3 of the smoothing circuit IO is connected to the output terminal T5, and further connected to the inverting input terminal of the operational amplifier 13 via a resistor Rj.

On the other hand, the output terminal of the operational amplifier 13 is connected to the output terminal T6, and is further negatively fed back to the inverting input terminal of the operational amplifier 13 via the variable resistor Rr.

Further, the output terminal of the operational amplifier 13 is connected to the inverting input terminal of the operational amplifier 13 via a resistor Rf, a correction coil L3 wound around the coil L1, and a resistor Rj.

Output terminal T5. Similar to the embodiment shown in FIG. 1, T6 is connected to a meter (not shown).

In other words, this embodiment is obtained by adding an operational amplifier 13 for correcting nonlinear output to the embodiment shown in FIG.

FIG. 4 shows an example of measurement according to this embodiment.

Here, coil L1. The number of turns of L2 is 100°1 f =
5.5 MΩ, I=40mA, Rr=780Ω, +E
=2-3V, f=125KHz, and the measured object 12 is a copper plate with a thickness of 2 mm.

〔Effect of the invention〕

As explained above, since the present invention uses an amorphous magnetic alloy as the magnetic core, it has good magnetic permeability, good responsiveness and sensitivity to high frequencies, and is stable against temperature changes.

The diameter of the object to be measured is related to the outer diameter of the thin magnetic core and has nothing to do with the coil diameter, so the measurement range is wide compared to the diameter of the sensing part, and there are no major restrictions on the conditions of use.

Furthermore, since the thin amorphous magnetic alloy has high magnetic permeability and high inductance, the number of turns of the coil is small and the outer diameter of the coil is small.The outer diameter of the sensor can also be made smaller, making it smaller and lighter.

Due to this reduction in size and weight, the inertial force of the movable object to be measured or the magnetic core for the magnetic sensor is reduced during measurement, so the strength of the support frame may be reduced, and mechanical responsiveness is improved.

Furthermore, the component includes an astable multivibrator that is connected to the actuation side coil and the dummy side coil and self-oscillates, and outputs an output corresponding to the distance between the object to be measured and the end of the magnetic core closer to the actuation side coil. The circuit configuration is simplified and the size and weight are reduced.

The second invention further converts the nonlinear output from the astable multivibrator into a linear output using a calculator, and uses a correction coil wound around the active coil to adjust the nonlinear output according to the type of the object to be measured. This has the effect of providing negative feedback to the operational amplifier and automatically correcting its amplification characteristics.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an embodiment of the first invention, FIG. 2 is an output characteristic diagram of the embodiment of FIG. 1, and FIG. 3 is a configuration diagram of an embodiment of the second invention. 144 is an output characteristic diagram of the embodiment shown in FIG. 3, FIGS. 5(a), (b), (c) and 6 are explanatory diagrams of the conventional device, and FIGS. 7 and 8 are diagrams of the conventional device. It is a characteristic diagram. 9...Magnetic core lO...Smoothing circuit 11-...Astable multivibrator 13...Operation amplifier Ll...Activating side coil L2...Dummy side coil L3...Correction coil Applicant: Kawatetsu Techno Research Co., Ltd. Representative Patent Attorney Yoshi Kosugi Male Patent Attorney Saito
Sum Rule Figure 2 x (Final m) (^)ll'loyo Figure 5 (a) (b) (c)

Claims (1)

[Claims] 1. A magnetic core consisting of an actuating coil, a dummy coil, an amorphous magnetic alloy wire inserted into the actuating coil and the dummy coil, and a self-containing coil connected to the actuating coil and the dummy coil. An astable multivibrator that oscillates and outputs an output corresponding to the distance between the object to be measured and the end of the magnetic core closer to the working side of the magnetic core, and an AC component removed from the output from the astable multivibrator to produce only a DC component. An eddy current sensor comprising a smoothing circuit that outputs. 2. A magnetic core consisting of an actuation side coil, a dummy side coil, an amorphous magnetic alloy wire inserted into the actuation side coil and the dummy side coil, and a magnetic core that is connected to the actuation side coil and the dummy side coil and self-oscillates. and an astable multivibrator that outputs an output corresponding to the distance between the magnetic core and the end of the working side coil, and a smoothing circuit that removes an alternating current component from the output from the astable multivibrator and outputs only a direct current component. , an operational amplifier that corrects a nonlinear output from the smoothing circuit to a linear output, and a correction coil that is wound around the operating coil and that corrects the amplification characteristics of the operational amplifier in accordance with the type of the object to be measured. An eddy current sensor characterized by: