JPH0695147B2 - Magnetic measuring device - Google Patents

Description

Detailed Description of the Invention a. OBJECT OF THE INVENTION [Industrial field of application] The present invention relates to two horizontal and vertical components of the earth's magnetism and the value of the total magnetic force thereof, or the value of a magnetic field that slightly changes in a large magnetism. The present invention relates to a magnetic measurement device that measures a minute magnetic field.

[Conventional technology]

Conventionally, to measure the three components of the earth's magnetism, the analog signal detected by the detection coil is converted to analog-to-digital, the signal is processed by digital storage and arithmetic processing to obtain the total magnetic force value, and the amount of change in the earth's magnetism is recorded. A geomagnetic measurement device for steady observation, which has a function such as to perform the above, is already known. On the other hand, in the geomagnetism measuring device, it is not a problem to use a high voltage as the power supply voltage of the analog amplification circuit to obtain high measurement accuracy when performing steady measurements of the geomagnetism, but volcanic observation for knowing the magma activity of the volcano For a geomagnetic field measuring device used for a geological survey or for a geomagnetic survey, or a magnetic field measuring device used for observing the movement of the earth's magnetic field, a portable magnetic field measuring device that is compact and can be powered by a battery so that it is convenient to carry is required. In addition, the measured magnetic value detected is ± 60000 nanotesla (n
(Referred to as T), a measurement accuracy of 0.1 nT is required. or,
A 15-bit converter is used for the A / D converter that converts the positive and negative analog signals required for a portable magnetic measurement device into analog-to-digital, but the reliable and reliable range is up to 13 bits. Yes, 10nT for ± 60000nT values
The following values were uncertain.

The geomagnetism measuring device according to the present invention is convenient to carry, is small in size, guarantees high measurement accuracy, uses a battery for the power source of the analog circuit for amplifying the geomagnetic measurement signal, and accurately measures the value of the geomagnetism of 1 nT or less. It is possible to read, and it is possible to measure the geomagnetic value of the constant magnetic field in the range of ± 60000nT, and the geomagnetic value of the fluctuating magnetic field changing in the geomagnetic field of ± 60000nT is within the accuracy of ± 300nT with an accuracy of 0.1nT or less. It is a geomagnetism measuring device configured to be readable, and when the amount of change in geomagnetism changes to ± 300 nT or more and deviates from the preset reference magnetism value, it can automatically follow the geomagnetic signal and perform automatic measurement. .

[Problems to be Solved by the Invention]

The present invention is capable of constantly measuring the value of the geomagnetic field of the constant magnetic field and the value of the magnetic field of the fluctuating magnetic field, which is convenient for carrying, is small and lightweight, and is configured so that the measuring accuracy of the fluctuating magnetic field can be measured at a value of 0.1 nT or less. In the geomagnetism measuring device, two analog amplification circuits with different amplification factors are prepared to amplify the geomagnetic signal, and the inputs of the two amplification circuits can be switched by the analog switch in the constant magnetic field measurement mode and the variable magnetic field measurement mode. While canceling the constant magnetic field and measuring the fluctuating magnetic field,
When the value of the earth's magnetism moves beyond the range of the fluctuating magnetic field, the preset value of the constant magnetic field is automatically reset so that the fluctuating magnetic field can be continuously measured. Further, in order to ensure the measurement accuracy when measuring the fluctuating magnetic field, the magnetic core of the magnetic detector is constructed so as to operate with a so-called zero bias magnetic field so that a bias magnetic field is not always applied. A negative feedback circuit is provided for the analog amplification voltage, and the negative amplification voltage of the analog amplification circuit output is the signal voltage through the voltage-current conversion circuit to the signal detection coil through the negative feedback circuit and the analog switch. Is output as. The magnetic measuring device of the present invention performs detection from a constant magnetic field for continuous measurement of a fluctuating magnetic field, setting, switching of an analog amplifier circuit, output of a measurement result to a display device, and calculation from two orthogonal components and a vertical component. This is a magnetic measuring device configured such that the total magnetic force value, the dip angle value, and the like are controlled and calculated using a microcomputer, and the measurement results can be displayed on a display device and continuously displayed on an external storage device.

B. Structure of the Invention [Means for Solving the Problems] The present invention, in order to amplify an analog signal obtained by measuring a detection signal from the signal detection coil SC forming one component of the magnetic detection element MSC, a high magnetic value is used. Two analog amplifier circuits, a low gain amplifier circuit LAC of the constant magnetic field measurement analog amplifier circuit and a high gain amplifier circuit HAC of the analog amplifier circuit used when measuring the varying magnetic field, are installed, and a signal detection coil SC and two Microcomputer between the analog amplifier circuits
Insert the analog amplification circuit changeover switch SW controlled by the signal of the CPU, and search the constant magnetic field, set the constant magnetic field value, and change the magnetic field when the variable magnetic field moves beyond the preset magnetic field value in the variable magnetic field measurement mode. The measurement procedure is automatically switched to continuously measure the fluctuating magnetic field, and the analog amplification circuit changeover switch SW is automatically switched according to the command from the microcomputer CPU, and the control, calculation, etc. It is performed by an arithmetic unit and a storage device. Further, in the embodiment of the magnetic measuring device of the present invention, ± 15V is used for the power supply voltage of the analog amplifier circuit, and the output of the analog magnetic signal is ± 15V for the analog-digital conversion to the value of ± 10V, and the constant magnetic field is applied. It is converted to ± 60000nT at ± 10V in the measurement mode, set to ± 300nT at ± 10V in the variable magnetic field measurement mode, and can accurately measure up to a value of 0.05nT in the variable magnetic field measurement mode.

In other words, the output of the analog amplifier circuit is passed through a multiplexer that switches the signal channel controlled by the output of the microcomputer, through an A / D converter that performs analog-digital conversion, and is taken into the microcomputer CPU and stored in the internal storage device. Remembered. On the other hand, in the fluctuating magnetic field measurement mode, if the measured magnetic field moves beyond the fluctuating magnetic field range, it automatically switches to the constant magnetic field measuring mode, and when the constant magnetic field is automatically canceled, the microcomputer CPU issues a constant magnetic field measuring mode command. The analog amplification circuit changeover switch SW is automatically switched and connected to the low gain amplification circuit LAC with a low amplification factor according to a command from the microcomputer CPU, and the measured value of the constant magnetic field analog-to-digital conversion is taken into the microcomputer CPU. The value of the taken-in constant magnetic field is supplied as a canceling current to the canceling coil through the digital-analog converter circuit A / D and the voltage-current converter circuit. Then, the mode is switched to the variable magnetic field measurement mode again, and the analog amplification circuit switching switch SW is
Switched to high gain amplifier circuit HAC when measuring fluctuating magnetic field,
After confirming with a microcomputer that the fluctuating magnetic field measurement range is within ± 300 nT, continuous measurement is performed in the fluctuating measurement mode. The fluctuating magnetic field to be measured is continuously measured and stored in the fluctuating magnetic field measurement mode, and the value of the magnetic field for each component is the value of the constant magnetic field added to the canceling coil in the constant magnetic field measurement mode or the value of the constant magnetic field fluctuates. It is calculated by either of the sum of the values of the magnetic field measured in the magnetic field measurement mode.

That is, the present invention is: 1. An analog circuit for amplifying a magnetic signal, an analog-digital converter, a microcomputer for storing a magnetic measurement value, a control calculation process, a digital-analog converter,
In a magnetic measurement device composed of a canceling circuit for canceling a constant magnetic field composed of a voltage-current conversion circuit and an exciting circuit for exciting the exciting coil of a magnetic detecting element consisting of a signal detecting coil, a canceling coil and an exciting coil, an analog amplifying circuit is provided. Two circuits, a low gain amplifier circuit and a high gain amplifier circuit, are prepared, an analog switch controlled by a microcomputer is provided on the analog circuit input side, and a predetermined magnetic field is used to measure the fluctuating magnetic field with high sensitivity. When the magnetic fluctuation exceeds the measurement range, the constant magnetic field value is automatically changed to continuously measure the fluctuation magnetic field.

2.For continuous measurement of fluctuating magnetic field, switch the analog signal amplification to the low gain amplification circuit by the start command, read the value of the geomagnetic constant magnetic field, detect the value of the canceling magnetic field, and detect the canceling voltage of the constant magnetic field to the canceling circuit. After the output, the analog amplifier circuit is switched to a high gain amplifier circuit, and the operation to add the minute residual magnetic field polarity judgment and the minute canceling magnetic field to the canceling circuit is repeated so as to be within the preset minute magnetic field range, and the minute magnetic field range is driven. After the range is satisfied, the fluctuating magnetic field is continuously measured, and when the value of the fluctuating magnetic field continuous measurement magnetic field exceeds the predetermined measuring range, the procedure for returning to the start is repeated under the control of the microcomputer and automatically. It is a magnetic measurement device configured to continuously measure a fluctuating magnetic field.

[Action]

The analog amplification circuit uses two circuits: a low gain amplification circuit that operates in the constant magnetic field measurement mode that detects and measures the geomagnetic component, and a high gain amplification circuit that operates in the fluctuation magnetic field measurement mode that detects and measures fluctuations in the geomagnetic field. However, since the two analog amplifier circuits are configured to connect an analog switch that allows a minute current to flow between the signal detection coil and the analog amplifier circuit and switch between the two analog amplifier circuits according to a control command of the microcomputer, Even if the power supply voltage of the amplifier circuit is low, switching to the variable magnetic field measurement mode enables accurate measurement of geomagnetic values of 0.1 nT or less. Further, in the fluctuating magnetic field measurement mode, when the measured magnetic field exceeds the preset fluctuating magnetic field range, it is detected by the microcomputer incorporated in the measuring device, and the fluctuating magnetic field measuring mode is automatically switched to the constant magnetic measuring mode. The value of the constant magnetic field of the geomagnetic component is measured, and the measured value is passed through the cancellation coil as the cancellation current value of the constant magnetic field by the digital-analog converter and the voltage-current conversion circuit, and the magnetic sensing element becomes a zero bias magnetic field and the fluctuation magnetic field measurement mode again. , The analog amplifier circuit was also switched to the high-gain amplifier circuit in the fluctuating magnetic field measurement mode, and it was confirmed that the fluctuating magnetic field satisfied the preset minute magnetic field range within ± 300 nT,
The magnetic measurement is continued again in the variable magnetic field measurement mode. In the fluctuating magnetic field measurement mode, the operation is repeated according to the procedure described above to continue the measurement in the fluctuating magnetic field measurement mode. 3 of the value of the constant magnetic field canceled during the measurement of the fluctuating magnetic field and the measured fluctuating magnetic field
The value of the component can be continuously recorded in the external recording device when the external recording device is connected, and the measured value of the fluctuating magnetic field for a short time is stored in the temporary storage device and displayed in the display device such as a liquid crystal display. Is displayed.

〔Example〕

 Embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a magnetic measuring device according to the present invention. A magnetic detecting element MSC for detecting a magnetic field of a fluxgate system includes an exciting coil DC for exciting the magnetic detecting element, a signal detecting coil SC for detecting a signal, and a constant magnetic field. It consists of a canceling coil CC for canceling, and three phases are prepared when measuring three components of the earth's magnetism. The output of the signal detection coil SC is an analog amplification circuit switching switch SW, a DC / AC amplification circuit AAC, and a DC amplification circuit A.
The measured values that have been digitally converted through C and the analog-digital converter ADC are taken into the CPU of the microcomputer that performs the operation of control calculation, and temporarily stored in the internal storage device MRY. Microcomputer CPU for fluctuating magnetic field measurement
Digital-to-analog conversion circuit for the value of constant magnetic field
The voltage is converted into an analog voltage value by the DAC, converted into a current value by the voltage-current conversion circuit VIC, and input as a cancellation current to the cancellation coil CC. In the conventional magnetic measurement device, there is one analog amplification circuit for each component of the magnetic detection element.
Since the power supply voltage of the analog amplifier circuit can be increased in the steady observation device, measurement of 1 nT or less is possible.

FIG. 1 shows a circuit block diagram of one component of the flux-gate type magnetic measuring device according to the present invention. The magnetic detection element MSC that detects the magnetic field is the exciting coil DC that drives the magnetic detection element and the signal detection coil SC that detects the signal as in the conventional case.
And a canceling coil CC that cancels the constant magnetic field, and three phases are prepared when measuring the three components of the earth's magnetism. The output of the signal detection coil SC is switched and connected to two amplification circuits with different amplification gains via an analog amplification circuit switching SW that switches the input of the low gain amplification circuit LAC and the high gain amplification circuit HAC, and the output of the amplification circuit Is a multiplexer MPX,
It is taken into a microcomputer CPU that stores, calculates, and controls signals via a DC amplification circuit AC and an analog-digital converter ADC. As described above, the analog amplifying circuit prepares a low gain amplifying circuit LAC and a high gain amplifying circuit HAC in the magnetic measuring device of the present invention, and switches to the high gain amplifying circuit HAC in the variable magnetic field measurement mode to perform high precision measurement. Is to do. In the analog amplifying circuit of the present invention, the low gain amplifying circuit LAC and the high gain amplifying circuit HAC are both negatively fed back to the signal detection coil by the negative feeding amplification circuit NFC which converts the signal voltage after the synchronous detection circuit into a current value. Therefore, the magnetic core forming the magnetic detection element always operates at the center of the magnetic hysteresis curve, and has a zero-bias excitation circuit configuration that does not cause an error due to asymmetric excitation. Since the value of the negative feedback current is extremely small and a value of microamperes, the analog amplifier circuit changeover switch SW uses an analog switch that passes microamperes. The magnetic measurement has a constant magnetic field measurement mode and a fluctuating magnetic field measurement mode.
When you enter the constant magnetic field measurement mode with the input key connected to the microcomputer CPU, the microcomputer CPU
Analog amplifier circuit changeover switch SW by command from
Is switched to A and the low gain amplifier circuit LAC is connected. The low gain amplification circuit LAC can measure magnetic fields up to ± 60000nT, and usually measures the constant magnetic field of the earth's magnetism and the total magnetic force.

Next, the variable magnetic field continuous measurement of the present invention will be described with reference to the flowchart showing the operation of the microcomputer shown in FIG. When commanded by the input key to the variable magnetic field measurement mode, measurement is started by the command of the microcomputer CPU, the analog amplification circuit switching SW is first switched to A to the low gain amplification circuit LAC, and the analog signal is digitalized by the analog-digital converter ADC. Converted to a signal, the constant magnetic field value is loaded into the microcomputer CPU, the numerical value is stored, and the data is read in the low sensitivity state. After confirming the amount of cancellation, the measured numerical value passes through the digital-analog converter DAC and the voltage-current conversion circuit VIC, becomes a cancellation current, and a current corresponding to a constant magnetic field is applied to the cancellation coil CC. Next, the analog amplification circuit changeover switch SW is switched to B, the high gain amplification circuit HAC is connected, and the measurement value of the high gain amplification circuit HAC passes through the analog-digital converter ADC and is taken into the microcomputer CPU. The measurement start in the fluctuating magnetic field measurement mode starts when the constant magnetic field is canceled to within ± 50nT by the canceling current and the condition of the minute magnetic field range ± 50nT is satisfied. Under the original condition, the constant magnetic field is canceled and the minute magnetic field is judged to be within the range of ± 50 nT, and it is equivalent to ± 10 nT of canceling magnetic field, which is the judgment of geomagnetic polarity and arbitrary canceling magnetic field, for example, the polarity of canceling the detected magnetism. This operation outputs the cancellation current to the cancellation circuit.
The measurement value is repeatedly read into the microcomputer CPU through the high gain amplifier circuit HAC until the condition of nT or less is satisfied.

When the canceling magnetic field is within the very small magnetic field range ± 50 nT, the value of the canceling magnetic field is stored in the internal storage device, the constant magnetic field is fixed, the fluctuating magnetic field is measured, and the measured value is recorded in the internal storage device. To an external recording device. If the fluctuating magnetic field is continuously measured, if the measuring magnetic field moves,
When the fluctuation exceeds the magnetic field measurement range of ± 300 nT, the analog amplification circuit changeover switch SW is automatically switched to the low gain amplification circuit LAC according to a command from the microcomputer CPU, and the fluctuation magnetic field measurement is repeated at the same stage as at the start.

In the fluctuating magnetic field measurement mode, the measurement range is ± 300 nT and ± 15 bits are converted, so even if the lower 2 bits become uncertain, the resolution is 0.05 nT, and the target accuracy of 0.1 nT is sufficiently secured. Moreover, it is automatically switched within the range of ± 300 nT and continuously measured. Since the measuring device of the present invention is made to be capable of continuously recording and displaying the measured value for a short time and connecting to an external recording device, the display of the short range of the measured value and the external recording of the measured value are performed. Continuous recording by the device is possible.

In the embodiment of the present invention, the fluctuating magnetic field measuring device is ± 30
The value of 0nT is set to the value of ± 50nT for the minute magnetic field for setting within the variable magnetic field measurement range, but ± 300nT, ± 50n
Of course, other magnetic field values may be used instead of fixing to the value of T.

C. Advantageous Effects of Invention The magnetic measuring device according to the present invention includes an analog amplifier circuit for amplifying a detection signal, which is a low gain amplifier circuit and a high gain amplifier circuit.
It is composed of a circuit, the input of the analog amplification circuit is an analog changeover switch that flows microamperes, the analog output is read and stored in the microcomputer through the analog-digital converter, and the output of the microcomputer is analog by the digital-analog converter. Converted to voltage, the analog voltage is supplied to the cancellation coil through the voltage-current conversion circuit, and the stationary magnetic field measurement and the fluctuation magnetic field measurement are controlled by the control procedure preset in the microcomputer, and the fluctuation magnetic field in a certain set magnetic field range is controlled. Magnetic measurement that can continuously measure automatically with high sensitivity, display the measurement result on a display device, connect to an external recording device connected to the measurement device for digital recording, and calculate the magnetic measurement value of the measurement result It is a device. Further, since the analog circuit is configured to switch operation depending on the measurement mode by using two circuits of a high gain amplifier circuit and a low gain amplifier, it is possible to perform a highly accurate measurement even with a low power supply voltage.
Therefore, it has become possible to provide a highly-sensitive magnetic measuring device having a portable size.

A high gain amplification circuit and a low gain amplification circuit are provided in the analog amplification circuit according to the present invention, and the high gain amplification circuit and the low gain amplification circuit are switched by the control of the microcomputer for continuous measurement of the fluctuation magnetic field. Of course, the method of performing continuous measurement while capturing the optimum measurement conditions can be applied to other types of magnetic measurement devices.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an outline of an analog circuit, a cancellation circuit, and a microcomputer peripheral of one component of the magnetic measuring device according to the present invention. FIG. 2 is a flow chart showing the control of each circuit by a microcomputer when continuously measuring a fluctuating magnetic field in the magnetic measuring device according to the present invention. FIG. 3 is a circuit diagram showing a measuring system for one component of a conventional magnetic measuring device. SC ... Signal detection coil, CC ... Cancellation coil, DC ...
Excitation coil, MSC ... Magnetic detection element, SW ... Analog amplification circuit selector switch, AAC ... AC / DC amplification circuit, A
C: DC amplification circuit, NFC: Negative feedback amplification circuit, MPX ...
Multiplexer, ADC ... Analog to digital converter, DAC
...... Digital-analog converter, VIC ... Voltage / current conversion circuit, DC ... Excitation circuit, CPU ... Microcomputer, D
PY: Display device, KEY: Input key, EMY: External recording device, A: Low gain amplification circuit side switch, B: High gain amplification circuit side switch, LAC: Low gain amplification circuit, HAC ... High gain amplifier circuit, MRY ... Internal storage device.

Claims (1)

[Claims] 1. A magnetic detection element for detecting a fluctuating magnetic field, an analog amplifier circuit for amplifying the magnetic detection signal, an analog-digital converter, and a microcomputer for performing storage control calculation processing of the magnetic measurement value of the fluctuating magnetic field. In a magnetic measurement device including a digital-analog converter, a cancellation circuit for canceling a constant magnetic field in the fluctuating magnetic field, and a cancellation coil, two circuits, a low gain amplification circuit and a high gain amplification circuit, are prepared for the analog amplification circuit, An analog switch controlled by a microcomputer is provided on the input side of the analog amplifying circuit, and the continuous measurement of the varying magnetic field is performed by first switching the analog amplifying circuit to a low gain amplifying circuit in response to a start command so as to maintain a constant value in the varying magnetic field. Read the value of the magnetic field and apply the above-mentioned constant magnetic field cancellation voltage to the cancellation circuit. After the input, the analog amplifier circuit is switched to the high gain amplifier circuit, and the operation of repeatedly determining the polarity of the residual minute magnetic field and applying the minute canceling voltage to the canceling circuit is repeated so that it falls within the preset measuring range of the minute magnetic field. When the value of the continuously measured magnetic field of the fluctuating magnetic field exceeds the predetermined measurement range, the command is returned to the start command again, and the analog amplifying circuit is turned off by the control of the microcomputer. A magnetic measuring device configured to continuously measure a fluctuating magnetic field by electrically returning the gain amplifying circuit and then returning to the high gain amplifying circuit.