JPS5853311B2 - Zanriyujikisokuteisouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a residual magnetism measuring device capable of detecting residual magnetism of an object to be measured without being influenced by a background magnetic field.

When the residual magnetism of the object to be measured is very weak, it is difficult to directly measure the residual magnetism with a magnetometer due to the surrounding magnetic field of the environment in which the object to be measured is placed.

Therefore, there is a need for a device that detects the surrounding magnetic field and cancels the background magnetic field by generating a magnetic field equal to the detected magnetic field in a Helmholtz coil.

However, the purpose of the present invention is to first magnetize the object to be measured in one direction, and then simultaneously measure the background magnetic field and the magnetic field emitted from the object to be measured, in order to eliminate the influence of the magnetic field due to the background such as earth's magnetism. The measured value when and then,
After magnetizing from the opposite direction to the above direction, only the residual magnetism of the object to be measured is measured by comparing the measured value with the measured value when the background magnetic field and the magnetic field of opposite polarity emitted from the object to be measured are simultaneously measured. An object of the present invention is to provide a residual magnetism measuring device characterized in that the residual magnetism can be measured.

This will be explained below with reference to the drawings.

FIG. 1 is a block diagram of the apparatus of the present invention.

Reference numeral 10 denotes a DC power supply that supplies current necessary for magnetizing the object to be measured 110 to the magnetizing coil 30.

20 is a polarity switching circuit for switching the direction of the current flowing through the magnetizing coil 30, and the switch sw1. sw3 is turned ON by a command from the timing control circuit 50.

Turn off.

40 is a magnetometer used to measure residual magnetism.

The magnetometer 40 includes various fluxgate type magnetometers, various types of magnetic thin film magnetometers, and various types of fluxgate type magnetic thin film magnetometers, and also includes magnetic thin film magnetometers, magnetic multi-type magnetometers, Hall elements, and the like.

Reference numeral 60 denotes a selection circuit, in which the magnetic field measured by the magnetometer 40 becomes an electrical signal, and the destination of this electrical signal is determined by a command from the timing control circuit 50.

Switch SW2 included in the selection circuit 60. SW
4 determines whether the output of the magnetometer 40 is sent to the first hold circuit 70 or the second hold circuit 80.

A computing unit 90 computes the difference or sum between the output of the first hold circuit 70 and the output of the second hold circuit 80.

Then, the calculation result is input to the display circuit 100,
The signal may be displayed as is, or it may be displayed after signal processing through a known differentiation circuit, filter circuit, or tuning amplifier.

Next, the measurement procedure will be explained with reference to the operation sequence explanatory diagram shown in FIG. 2.

Periodically repeated pulse train P1 to P4 shown in FIG.
The command pulses output from the timing control circuit 50 are arranged on the time axis.

As can be seen from the figure, first, when a command pulse P1 is issued, the switch SW1 is turned on.

This indicates that the DC power supply 10 and the magnetizing coil 30 are in a connected state, and this state will be referred to herein as N-direction magnetization.

However, the magnetic flux level of the object to be measured 110 magnetized in the N direction decreases to the residual magnetic flux value when the switch SW1 is turned off.

The magnetic flux value at this time is set as Br.

Next, SW2 is turned ON by the command pulse P2, and an electric signal corresponding to the sum Hs+Hr of the surrounding magnetic field Hs measured by the magnetometer 40 and the magnetic field Hr emitted from the object to be measured 110 is input to the first hold circuit 70 and switched SW2 is OF
Even after reaching F, the value is held or stored.

Next, when the switch SW8 of the polarity switching circuit 20 is turned ON by the command pulse P3, the DC power supply 10 and the magnetizing coil 30 are connected so that the current flows in the opposite direction to that when the switch SW1 is ON. The measurement object 110 will be magnetized in the opposite direction.

This will be referred to as S-direction magnetization.

When the switch SW3 is turned OFF, magnetization in the S direction is completed, and then the switch SW4 is turned ON by the command pulse P4.

In this case, the magnetic field measured by the magnetometer 40 is Hs-Hr.

The electrical signal corresponding to this is then sent to the second hold circuit 8.
It is input to 0.

For example, if the arithmetic unit 90 is a subtracter, at its output (Hs+Hr)-(Hs-Hr)=2Hr
An electrical signal corresponding to this will be obtained.

Since this 2Hr has a correlation with twice the residual magnetic flux value, that is, 2Br, it is possible to accurately measure Br regardless of the surrounding magnetic field Hs by performing the necessary calibration for this electric signal.

FIG. 3 shows the circuit of a magnetic oscillation type magnetometer as one of the magnetometers 40 used in the present invention.

This magnetic oscillation type magnetometer has a circuit consisting of a magnetic core 1 and switching transistors Q1, Ql, and Q2, in which the switching transistors are turned on.

This magnetometer is configured to turn off by nonlinear characteristics in the unsaturated region of the magnetic core 1, and to detect information regarding the magnetic field Hs±Hr applied to the magnetic core 1 from the voltage eout between the terminals of a dummy resistor Ro inserted in this circuit. be.

FIG. 3a shows a magnetic oscillation type magnetometer constructed by a single switching transistor.

It is clear that the magnetic flux level of the magnetic core 1 is defined by the magnetic field Hs±Hr.

Therefore, when the power supply Ed is first applied, the current flows from the positive terminal of Ed through the bias resistor RB5 to the transistor Q1.
flows at the pace of , passes through the dummy resistor RO and enters the negative electrode of Ed.

This current causes a collector current to flow through Q1→RO→Ed→coil 3, and a voltage is induced in coil 2, thereby increasing the base current of transistor Q1.

That is, due to the positive feedback effect, the collector current of the transistor Q1 increases rapidly, and the transistor Q becomes conductive.

However, since the magnetic core 1 has nonlinear characteristics in the unsaturated region, the value of the differential permeability of the magnetic core 1 gradually decreases as the collector current increases, the induced voltage in the coil 2 decreases, and the collector current of the transistor Q1 decreases. , finally transistor Q1 becomes non-conductive.

Since no collector current is flowing at this point, the magnetic flux level of the magnetic core 1 returns to the initial magnetic flux level.

Magnetic oscillation occurs by periodically repeating the above cycle.

In this magnetic oscillation circuit, the level fluctuation of the magnetic field to be measured is converted into a change in the average value of the voltage eout between the terminals of the dummy resistor RO, so the strength and polarity of the magnetic field Hs±Hr are It is possible to know.

FIG. 3 shows an embodiment of a magnetic oscillation type magnetometer using two transistors Ql and Q2.

The magnetic field Hs±Hr is applied to the magnetic core 1 from the direction shown in the figure.

Figure 3C shows four coils 2 in the circuit shown in Figure 3S.
, 3, 4, 5 are reduced to two coils 2, 3.

Note that the magnetic oscillation operation is performed by the transistor Q1. Q1 is alternately O
If you pay attention only to repeating N and OFF, Figure 3a
It is omitted because it can be easily understood by explaining the operation.

As is clear from the above description, the apparatus of the present invention can be widely applied to quality control based on residual magnetic flux values, measurement of the amount of ferrite in stainless steel materials, discrimination or detection of foreign materials, discrimination of magnetic and non-magnetic materials, etc.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the device of the present invention, Fig. 2 is an explanatory diagram of the operation of the device of the present invention, Fig. 3 shows an embodiment of a magnetometer used in implementing the device of the present invention, and Fig. 3a shows a single A magnetic oscillation magnetometer configured with switching transistors,
Figure 3 shows a magnetic oscillation type magnetometer configured with two switching transistors, and Figure 3C shows a magnetic oscillation type magnetometer configured with two instead of the four coils in the embodiment shown in Figure 3. Each shows a magnetometer. 10 is a DC power supply, 60 is a selection circuit, 20 is a polarity switching circuit, 30 is a magnetizing coil, 40 is a magnetometer, 50 is a timing control circuit, 10 is a first hold circuit, 80 is a second hold circuit, 90 is a calculation 100 is a display circuit, 1
10 is the object to be measured.

Claims (1)

[Claims] 1. A DC power supply for magnetizing the object to be measured, a magnetizing coil, a polarity switching circuit for switching the magnetization direction, a magnetometer for measuring the magnetism after magnetization, and the output of this magnetometer. a selection circuit for sorting, first and second hold circuits for storing the measured values of the magnetometer, an arithmetic unit for calculating the outputs of these two hold circuits, and an output of this arithmetic unit. What is claimed is: 1. A residual magnetism measuring device comprising: a display circuit for displaying the above information; and a timing control circuit for controlling the order of operation of each of the above circuits.