JPS62242875A - Magnetic field measuring instrument - Google Patents

Abstract

PURPOSE:To simplify circuits by composing an exciting signal generating circuit of a rectangular wave pulse generating circuit and a detecting circuit of a timer circuit and a sample holding circuit. CONSTITUTION:A single-shot rectangular exciting signal Pk which has pulse width tau and a voltage Vd is supplied from the rectangular pulse generating circuit 20 to an exciting coil 1b wound around an annular magnetic core 1a. At this time, a signal Pk resonates at a frequency of 2tau cycles by a capacitor 3 connected in parallel to a detection coil 1c. The timer circuit 40a outputs a sample control signal Ps for tau/2 from the falling time t0 of the signal Pk to t1. The sample holding circuit 40b is supplied with the signal Ps at a terminal S from the time t0 to t1, so the voltage value of a detection signal Pb appears at a terminal O as a sample signal Pp. The signal Ps is not supplied to the terminal S after the time t1, so the voltage value Vp of the signal Pb at the time t1 is outputted continuously from the terminal O as the signal Pp. The voltage value Vp is proportional to the intensity Hs of an external magnetic field, so the intensity Hs of the external magnetic field is measured by measuring the voltage value Vp of the signal Pp after the time t1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to improvements in magnetic field measuring devices, and particularly to simplification of circuits and reduction in power consumption.

[Conventional technology]

A magnetic field measuring device as shown in Fig. 2 has been proposed.

In FIG. 2, reference numeral 1 denotes a fluxgate type magnetic sensor, which includes an annular magnetic core 1a made of a high magnetic permeability material, an excitation coil 1b wound around the annular magnetic core 1a, and the annular magnetic core 1a.
It is composed of a detection coil 1C wound on an axis passing through the center of a. Reference numeral 2 denotes an excitation signal generation circuit, which supplies an excitation signal Pd to the excitation coil 1b. 3 is a capacitor, which is connected in parallel with the detection coil 1C. 4 is a detection circuit, which is composed of a detection circuit 4a and a smoothing circuit 4b. The detection circuit 4a detects the detection signal pm output from the detection coil 1C and outputs a detection signal pe. The smoothing circuit smoothes the detected signal pa and outputs a smoothed signal po.

Next, the operation of the magnetic field measuring device having the above configuration will be explained.

The excitation signal Pd supplied from the excitation signal generation circuit 2 to the excitation coil 1b wound around the annular magnetic core 1a of the fluxgate type calm air sensor is shown in FIG. 3 (al). The excitation signal Pd has a period T and a pulse Width τ.

It is an alternating pulse signal with a voltage value ±vd, that is, an alternating pulse signal in which the voltage value switches in the order of +Vd, 0, -Vd, 0 for each time width τ during the period T, and the voltage value is d is a voltage value that can bring the annular magnetic core 1a into a sufficiently supersaturated state. On the other hand, the capacitance value C of the capacitor B is determined so that the relationship with the inductance L of the detection coil 1C is T/2=2πV/L. As a result, the detection signal pa, which is the output of the detection coil 1C, resonates at a period of half T, which is the period of the excitation signal Pd, that is, a period of 2τ. The waveform of the detection signal pa at this time is shown in Figure 3 (b
Shown in l. This detection signal PII is Pa=-AIIH3・-・51n(π・−)
(1) 4τ τ 01 It can be expressed as a sine wave with a period of 2τ.

(For example, Journal of the Institute of Electrical Engineers of Japan 5l-C13,) Here, A is a constant determined by the structure of the annular magnetic core, etc., and Hll is the strength of the external magnetic field applied to the detection coil 1C. If the voltage of the peak value (positive side) of the detection signal pa is Vp, then V p =-A 111-1g ・

(214τ), and it can be seen that the voltage Vp at the peak value is proportional to the strength H of the external magnetic field.The detection circuit 4a of the detection circuit 4 is supplied with the detection signal P, as shown in FIG. 3(C). The absolute value of the detection signal pm is combined with the detection signal P and output as shown in FIG.
e is supplied and smoothed to a voltage connecting the vertices of the detection signal pg as shown in FIG. The value of voltage Vp is converted to a DC voltage whose voltage value is Vp, and is output as a smoothed signal po from the smoothing circuit 4b of the detection circuit 4. Therefore, as shown in equation (2), the DC voltage Voltage value V.

Since is proportional to the strength H8 of the external magnetic field, the strength H of the external magnetic field can be measured by measuring the DC voltage value Vp.

[Problem that the invention seeks to solve]

As described above, the excitation signal Pd, which is an alternating pulse signal output from the excitation signal generation circuit 2, is applied to the excitation coil 1b, and is output from the detection coil 1C and the capacitor 6 connected in parallel to the detection coil 1C. The detection signal pm is converted into a detection signal P by the detection circuit 4a of the detection circuit 4, and the detection signal P is further converted into a smoothed signal po which is a DC voltage by the smoothing circuit 4b, and the voltage value of the smoothed signal po is By measuring this, the strength H of the external magnetic field was measured.

However, since the excitation signal generation circuit 2 generates the excitation signal Pd which is an alternating pulse signal, the circuit configuration becomes complicated, and the detection circuit 4 also has a detection circuit 4a and a smoothing circuit 4.
b, the circuit becomes complicated. Furthermore, since the excitation signal generation circuit 2 constantly generates the excitation signal pa, which is an alternating pulse signal, and continues to supply it to the excitation coil, there is a problem in that power consumption increases. The purpose of the present invention is to solve the above problems,
The present invention provides a magnetic field measuring device with a simple circuit configuration and low power consumption.

[Failure to solve the problem]

In order to achieve the above object, the present invention has the following configuration. That is, the magnetic field measurement device of the present invention includes a ring-shaped magnetic core made of a high magnetic permeability material, an excitation coil wound around the ring-shaped magnetic core, and a detection coil wound on an axis passing through the center of the ring-shaped magnetic core. A magnetic field measuring device comprising: a fluxgate magnetic sensor; an excitation signal generation circuit that supplies an excitation signal to the excitation coil; and a detection circuit that is connected to the detection coil to detect the strength of an external magnetic field. , the excitation signal generation circuit is a rectangular pulse generation circuit that generates a rectangular pulse, and the detection circuit includes a timer circuit that operates using the rectangular pulse as a synchronization signal and a sample hold circuit that operates based on the output signal of the timer circuit. It is characterized by

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. 1st
The figure is a block diagram of a magnetic field measuring device according to the present invention. In FIG. 1, the same elements as those in FIG. 2 are given the same numbers and their explanations will be omitted. In FIG. 1, reference numeral 20 denotes a rectangular pulse generation circuit which is an excitation signal generation circuit, and the rectangular excitation signal P is transmitted to the excitation coil 1 of the fluxgate type sharpening sensor 1.
b. A detection circuit 40 is composed of a timer circuit 40a and a sample and hold circuit 40b. The timer circuit 40a is the same as the rectangular pulse generating circuit 20.
A rectangular excitation signal PK output from the terminal φ is supplied to the terminal φ, and the rectangular excitation signal Pr.

A sample control signal P, which is a single pulse with a pulse width τ/2, is output in synchronization with the falling edge of . Further, the sample and hold circuit 40b has a terminal I supplied with a detection signal Pb outputted from the detection coil 1C of the fluxgate magnetic sensor 1 and a capacitor 6 connected in parallel to the detection coil 1C, and further includes the timer circuit 40a. A sample control signal Ps output from the terminal S is supplied to the terminal S. When the sample control signal P8 is supplied to the terminal S, the sample hold circuit 40b outputs the detection signal pb input to the terminal ■ as it is from the terminal 0 as the sample signal Pp, and outputs the sample control signal P8 to the terminal S as it is. signal pH
is not supplied, the voltage value of the detection signal pb at the time when the sample control signal PIl is no longer supplied continues to be output as the sample signal Pp.

The operation of the magnetic field measuring device having the above configuration will be explained.

A rectangular excitation signal PK supplied from the rectangular pulse generation circuit 20, which is an excitation signal generation circuit, to the excitation coil 1C wound around the annular magnetic core 1a is shown in FIG. 4 (al).The rectangular excitation signal P3 has a pulse width τ is a single pulse signal with a voltage value vd, and the voltage value ■d is a voltage value that can sufficiently bring the annular magnetic core 1a into a supersaturated state.At this time,
A detection signal P is the output of the detection coil 1C. The capacitor B connected in parallel with the detection coil 1C resonates at a period of 2τ as already explained. The detection signal pb
The waveform of is shown in FIG. 4 (bl).While the conventional excitation signal Pd shown in FIG. 2 is an alternating pulse signal, the rectangular excitation signal P of the present invention is a single pulse signal, so Since it is not excited, the equation (11) is multiplied by the attenuation function f (tt) determined by the circuit constant. Since f(t1) is constant, f(t1) is also a negative value, and therefore, it can be seen that the voltage Vp at the peak value is proportional to the strength H of the external magnetic field.

The timer circuit 40a outputs the sample control signal P for τ/2 from the time t when the rectangular excitation signal PK falls to the time t, as shown in FIG. 4 (C1).The sample and hold circuit 40b , sample control signal P8 to terminal S
is time t. Since the fourth
As shown in the figure (dl), the voltage value of the detection signal Pb is directly output from the terminal O as the sample signal PP. Since the sample control signal P is no longer supplied to the terminal S after time 1, the detection signal at time t1 The voltage value of Pb, that is, the voltage value Vp, continues to be output as the sample signal Pp from the terminal O. Therefore, as shown in equation (4), the voltage value Vp
, is proportional to the strength of the external magnetic field H8, so that time 1
．． By measuring the voltage value Vp of the subsequent sample signal TIP, the strength H8 of the external magnetic field can be measured.

〔Effect of the invention〕

As described in detail above, according to the present invention, a rectangular pulse generation circuit that generates a single pulse signal is used as the excitation signal generation circuit, and a timer circuit and a sample hold circuit are used as the detection circuit, so that the circuit configuration can be relatively simplified. Furthermore, since the magnetic field can be measured only by supplying a rectangular excitation signal once to the excitation coil, power consumption is reduced (
It is effective for application as a portable measuring device.

[Brief explanation of drawings]

FIG. 1 is a professional diagram of the magnetic field measuring device according to the present invention, and FIG.
The figure is a block diagram of a conventional magnetic field measuring device, and FIG. 3 is a time chart for explaining the operation of the conventional magnetic field measuring device.
FIG. 4 is a time chart for explaining the operation of the magnetic field measuring device according to the present invention. 1...Fluxgate type magnetic sensor, 1a.
......Annular arsenic core, 1b...Exciting coil, 1
C...Detection coil. 20... Rectangular pulse generation circuit, 40a...
...Timer circuit, 40b...Sample hold circuit. Figure 4

Claims (1)

[Claims] A fluxgate type magnetic sensor configured with an annular magnetic core made of a high magnetic permeability material, an excitation coil wound around the annular magnetic core, and a detection coil wound on an axis passing through the center of the annular magnetic core; In the magnetic field measuring device, the excitation signal generation circuit includes an excitation signal generation circuit that supplies an excitation signal to the excitation coil, and a detection circuit that detects the strength of an external magnetic field by being connected to the detection coil, wherein the excitation signal generation circuit generates a rectangular pulse. A magnetic field measuring device, characterized in that the detecting circuit is comprised of a timer circuit that operates using the rectangular pulse as a synchronizing signal, and a sample hold circuit that operates based on the output signal of the timer circuit.