JP2005083868A - Magnetic measuring device - Google Patents

Abstract

Dynamic range, linearity, and resolution are improved in a magnetic measurement apparatus using a fluxgate type magnetic detection element.
A flux gate type magnetic detection element 10 having a magnetic core 11, an excitation coil 12, and a detection coil 13, an excitation unit 50 for supplying an alternating current to the excitation coil 12, and a detection coil 13 are induced. A magnetic detection unit 30 that processes a signal to output a magnetic detection signal Vp, a first integrator 41 that integrates the magnetic detection signal Vp and outputs a first integration signal Vi1, and a first integration signal Vi1. A second integrator 42 that integrates and outputs a second integrated signal Vi2, an adder 21 that adds the first to second integrated signals and outputs an added signal Vd, and a feedback signal Ib based on the added signal Vd And a feedback circuit 26 for returning the signal to the detection coil 13 side.
[Effect] It is possible to measure weak magnetism such as cardiac magnetism by using a fluxgate type magnetic detecting element.
[Selection] Figure 1

Description

  The present invention relates to a magnetic measurement apparatus, and more particularly, to a magnetic measurement apparatus that can improve dynamic range, linearity, and resolution in a magnetic measurement apparatus using a fluxgate magnetic detection element.

2. Description of the Related Art Conventionally, a magnetic measurement apparatus using a flux gate type magnetic detection element is known (for example, see Patent Document 1).
On the other hand, the applicant of the present application integrates the output signal of the non-linear magnetic detection means having non-linear detection characteristics with respect to magnetism by a multi-stage integrator, and adds the output signals of the integrators of each stage to create a feedback signal, A magnetic measuring device that returns a feedback signal to the non-linear magnetic detection means side has been proposed (see Patent Document 2).
JP 2003-121521 A JP 2001-133528 A

The dynamic range of a magnetic measuring device using a conventional fluxgate type magnetic sensing element is, for example, 1 nT / √ {Hz} to 1 mT / √ {Hz}, the linearity is narrow, and the resolution is, for example, 1 nT / √ {Hz}. Yes, it was possible to measure the magnetism of the geomagnetism, but it was difficult to measure weak magnetism such as cardiac magnetism.
Accordingly, an object of the present invention is to provide a magnetic measuring apparatus that improves the dynamic range, linearity, and resolution in a magnetic measuring apparatus using a fluxgate type magnetic sensing element, and can measure weak magnetism such as cardiac magnetism. It is to provide.

In a first aspect, the present invention relates to a flux gate type magnetic detection element including a magnetic core, an excitation coil, and a detection coil, an excitation unit that supplies an alternating current to the excitation coil, and induction in the detection coil. A magnetic detection unit that processes the processed signal and outputs a magnetic detection signal; a first integrator that integrates the magnetic detection signal and outputs a first integration signal; an nth integrator that outputs n (= 2 to N, N ≧ 2) integration signals, an adder that adds the first to Nth integration signals and outputs an addition signal, and the addition signal There is provided a magnetic measuring device comprising a feedback section for returning a feedback signal based on the feedback signal to the detection coil side.
In the magnetic measurement apparatus according to the first aspect, the dynamic range, linearity, resolution, and resolution are obtained by sharing the extraction of the signal components of each band when the wide band is divided into N bands into N stages of integrators. Can be improved. For example, the dynamic range can be improved to 1 pT / √ {Hz} to 1 mT / √ {Hz}, the linearity can be improved 10 times or more, and the resolution can be improved to 1 pT / √ {Hz}. Therefore, it is possible to measure even weak magnetism such as cardiac magnetism.

In a second aspect, the present invention provides a magnetic measurement apparatus having the above configuration, wherein N = 2 or N = 3.
In the magnetic measurement apparatus according to the second aspect, the dynamic range is obtained by sharing the extraction of the signal components of each band when the wide band is divided into two or three bands with each of the two-stage or three-stage integrators. And linearity and resolution can be improved. For example, the dynamic range can be improved to 1 pT / √ {Hz} to 1 mT / √ {Hz}, the linearity can be improved 10 times or more, and the resolution can be improved to 1 pT / √ {Hz}. Therefore, it is possible to measure even weak magnetism such as cardiac magnetism.

In a third aspect, the present invention provides the magnetic measurement apparatus having the above configuration, in which the first to Nth integral signals are attenuated / amplified between the first to Nth integrators and the adder. There is provided a magnetic measurement apparatus provided with the first to Nth integral signal conditioners.
In the magnetic measurement apparatus according to the third aspect, the signal component of each band is emphasized by attenuating or amplifying the signal component of each band when the wide band is divided into N bands, and the signal of the undesired band Ingredients can be suppressed.

In a fourth aspect, the present invention provides a magnetism measuring apparatus having the above-described configuration, further comprising a feedback amount adjuster for adjusting a feedback amount for returning the feedback signal to the detection coil side. Provide a measuring device.
In the magnetic measurement apparatus according to the fourth aspect, the sensitivity can be adjusted by adjusting the feedback amount.

  According to the magnetic measurement apparatus of the present invention, the dynamic range, linearity, and resolution can be improved in the magnetic measurement apparatus using the fluxgate type magnetic detection element, and weak magnetism such as cardiac magnetism can be measured.

  Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is a configuration diagram illustrating a magnetic measurement apparatus 100 according to the first embodiment.
The magnetic measurement apparatus 100 includes a flux gate type magnetic detection element 10 including a magnetic core 11, an excitation coil 12, and a detection coil 13, an excitation unit 50 that supplies an alternating current to the excitation coil 12, and a detection coil 13. A feedback circuit 26 that superimposes the feedback signal Ib on the detection signal Is induced by the magnetic signal, a magnetic detection unit 30 that processes the detection signal Is superimposed on the feedback signal Ib and outputs a magnetic detection signal Vp, and a magnetic detection signal Vp. A first integrator 41 that integrates and outputs a first integrated signal Vi1, a second integrator 42 that integrates the first integrated signal Vi1 and outputs a second integrated signal Vi2, and first to Nth The first to Nth integrated signal regulators 201 to 202 for attenuating / amplifying the integrated signals Vi1 to Vi2 and the first to second integrated signals Vi1 ′ to Vi2 ′ having passed through the integrated signal regulators 201 to 202 are added. To output the addition signal Vd. An adder 21, a feedback amount adjuster 22 for attenuating / amplifying the added signal Vd to adjust sensitivity, and a bias for adding the bias signal Va to the added signal Vd 'that has passed through the feedback amount adjuster 22 and outputting the feedback signal Ib And a regulator 23.

  The fluxgate type magnetic sensing element 10 includes an excitation coil 12 and a detection coil 13 formed on a magnetic core 11 formed in an annular shape from a material having soft magnetic properties (low coercive force and high magnetic permeability) such as permalloy or sendust. However, a structure in which an excitation coil and a detection coil are attached to a rod-shaped magnetic core may be used.

  The excitation unit 50 includes an oscillator 51 that oscillates a rectangular wave having a frequency f0 (for example, f0 = 2 kHz), and a coil that divides the rectangular wave oscillated by the oscillator 51 and energizes the excitation coil 12 with an alternating current having a frequency f0 / 2. And a drive circuit 52.

  The magnetic detector 30 includes a phase shifter 31 that outputs a synchronization signal shifted in phase from the excitation phase shift of the fluxgate magnetic detection element 10, and a preamplifier 32 that amplifies the detection signal Is superimposed with the feedback signal Ib. A high-pass filter 33 for cutting off the excitation signal component at the cut-off frequency fc1 (> f0 / 2), a phase detector 34 for detecting the phase of the output signal from the high-pass filter 33 using a synchronization signal, and a cut-off frequency fc2 (<< and a low-pass filter 35 for extracting a signal component in a desired band at f0).

The first integrator 41 integrates the magnetic detection signal Vp with a time constant τ1, and outputs a first integration signal Vi1.
The second integrator 42 integrates the first integration signal Vi1 with a time constant τ2 (> τ1), and outputs a second integration signal Vi2.

  The bias signal Va is adjusted so that the addition signal Vd becomes 0 when the magnetism to be measured is 0 (that is, the DC component of noise magnetism is canceled).

  According to the magnetic measurement apparatus 100 of the first embodiment, the fluxgate type magnetic detection element 10 is used. However, since the broadband signal component is shared by the two integrators 41 and 42, the dynamic range, linearity, resolution, It is possible to measure weak magnetism such as cardiac magnetism, which has been difficult in the past.

FIG. 2 is a configuration diagram illustrating a magnetic measurement apparatus 200 according to the second embodiment.
In the magnetic measurement apparatus 200, a third integrator 43 is added to the subsequent stage of the second integrator 42 of the magnetic measurement apparatus 100 according to the first embodiment, and the third integration signal output from the third integrator 43 is added. A third integrated signal adjuster 203 for attenuating / amplifying Vi3 is added, and the first to third integrated signals Vi1 ′ to Vi3 ′ having passed through the first to third integrated signal adjusters 201 to 203 are added by an adder 21. It is comprised so that it may add.

  The time constant τ3 of the third integrator 43 satisfies the relationship τ1 <τ2 <τ3.

  According to the magnetic measurement apparatus 200 of the second embodiment, the fluxgate type magnetic detection element 10 is used. However, since the broadband signal component is shared by the three integrators 41, 42, and 43, the dynamic range and linearity are The resolution can be further improved, and it is possible to measure weak magnetism such as cardiac magnetism, which has been difficult in the past.

Four or more integrators may be connected in multiple stages.
Note that the time constant of the integrator is made larger than the time constant of the integrator one stage before.

  It is possible to measure weak magnetism such as cardiac magnetism using a fluxgate type magnetic sensing element.

It is a block diagram which shows a magnetic measurement apparatus. (Example 1) It is a block diagram which shows a magnetic measurement apparatus. (Example 2)

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Flux gate type magnetic detection element 11 Magnetic core 12 Excitation coil 13 Detection coil 21 Adder 22 Feedback amount adjuster 23 Bias adjuster 26 Feedback circuit 30 Magnetic detection part 31 Phase shifter 32 Preamplifier 33 High pass filter 34 Phase detection Unit 35 Low-pass filter 41 First integrator 42 Second integrator 43 Third integrator 50 Excitation unit 51 Oscillator 52 Coil drive circuit 100, 200 Magnetic measurement device 201 First integration signal adjuster 202 Second integration Signal conditioner 203 Third integrated signal conditioner

Claims (4)

  A flux gate type magnetic detection element including a magnetic core, an excitation coil, and a detection coil, an excitation unit that supplies an alternating current to the excitation coil, and a magnetic detection signal by processing a signal induced in the detection coil , A first integrator that integrates the magnetic detection signal and outputs a first integration signal, and an integration signal of the previous stage is integrated to obtain an nth (= 2 to N, N ≧ 2). ), An adder for adding the first to Nth integration signals and outputting an addition signal, and a feedback signal based on the addition signal to the detection coil side. A magnetic measuring device comprising a feedback unit for returning.   The magnetic measurement apparatus according to claim 1, wherein N = 2 or N = 3.   3. The magnetic measurement apparatus according to claim 1, wherein the first to Nth integration signals are attenuated / amplified between the first to Nth integrators and the adder. A magnetic measuring device provided with an Nth integral signal conditioner.   4. The magnetism measuring apparatus according to claim 1, further comprising a feedback amount adjuster for adjusting a feedback amount for returning the feedback signal to the detection coil side. measuring device.

Images