JPH09329656A - SQUID type magnetic force measuring device - Google Patents

Abstract

(57) [Summary] [Object] To obtain an SQUID type magnetic force measuring device which realizes more accurate magnetic field measurement by avoiding an error caused by discharge transient characteristics of an integrator in a FLL drive circuit. [Structure] When the coarse-fine synthesizer 5 for adding the coarse data and the fine data is detected and the coarse pulse is detected, the output of the coarse-fine synthesizer 5 is held at the output of the coarse-fine synthesizer 5 immediately before the detection of the coarse pulse for a certain period of time. Equipped with a ranking controller.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention SQUID (superconducting quantum interference device; S uperconducting Qu a
ntum I nterferece D evice) relates force measuring apparatus using the sensor.

[0002]

2. Description of the Related Art FIG. 7 is a block diagram of a conventional SQUID type magnetic force measuring apparatus. In FIG. 7, reference numeral 1 denotes a SQUID sensor for detecting a magnetic field, 2 linearly converts and outputs a periodic voltage change with respect to an input magnetic field change of the SQUID sensor, and its output is an arbitrary predetermined one of the above periodic voltage changes. When the voltage value corresponding to the number of cycles is reached, this is reset and a FLL (Flux L) that outputs a pulse (coarse pulse) indicating that this reset operation has been performed.
ocked Loop) drive circuit, 3 is an A / D converter that converts the voltage output of the FLL drive circuit 2 into digital amount data (referred to as fine data), and 4 counts the cumulative number of the rough pulses and resets Data obtained by an integral multiple of the amount of magnetic field corresponding to the number of cycles performed (referred to as coarse data).
A coarse measuring device 5 for converting to and outputting to a coarse measuring device 5 for adding the rough data and the fine data and outputting the detected magnetic field amount.

Next, the operation will be described. As shown in FIG. 8, the SQUID sensor 1 has the B-V characteristic that the voltage V changes periodically with respect to the change of the input magnetic field B, and therefore the voltage V is not uniquely determined with respect to the magnetic field B and is high. Not suitable for measuring dynamic range. The FLL drive circuit 2 has a periodic B of the SQUID sensor 1 as described above.
SQU is a circuit that converts the -V characteristic into a linear voltage output.
Based on a method of fixing an operating point (for example, a valley portion) on the BV characteristic by generating a feedback magnetic field having an opposite sign to the input magnetic field to the ID sensor 1, a predetermined BV as shown in FIG. The characteristic n cycle (n is an integer) is the maximum voltage, and a linear voltage proportional to the magnitude of B is output to the A / D converter 3, and when the n cycle is exceeded, this voltage output is generated. The coarse pulse is output to the coarse measuring device 4 at the same time that the integrator of is reset to the zero point. A / D converter 3 is FLL
The voltage output of the drive circuit 2 is converted into a digital amount and output to the coarse and fine synthesizer 5 as fine data. Further, the coarse measuring device 4 is FL
The cumulative number of coarse pulse outputs of the L drive circuit 2 is multiplied by the magnetic field amount B corresponding to the predetermined number of cycles, and a value corresponding to an integral multiple of the n cycles is output to the coarse refiner synthesizer 5 as coarse data. . Therefore, when the input magnetic field to the SQUID sensor 1 increases at a constant rate of change, the coarse data is stepwise output and the fine data is sawtooth output as shown in the timing 1. The magnetic field amount detected by the SQUID is obtained by performing the addition.

[0004]

The ideal coarse synthesis in the conventional SQUID type magnetic force measuring device is shown at timing 1 in FIG. FIG. 10 shows that when the input to the SQUID sensor 1 increases linearly with time, the fine data output from the FLL drive circuit 2 converted into a digital amount is converted into a coarse data and a coarse refinement synthesizer. 5
It is made to correspond to the data after the crude refinement synthesis which is the output of. Ideally, the zero reset of the fine data and the output of the coarse data are performed at the infinitesimally small coincident times, and the output after the coarse refinement smoothly and linearly increases as shown here. Here, the configuration of the actual FLL drive circuit 2 will be described in more detail. F
As shown in FIG. 13, the LL driving circuit 2 inputs the feedback magnetic field modulated by the oscillator 11 to the SQUID sensor 1 from the feedback coil 12, and multiplies the change of the external magnetic field by the output of the oscillator 11 via the resonance circuit 13. After being multiplied by the device 14, it is converted into a voltage output through the integrator 15. In an actual circuit, of course, the integrator 15
Has a characteristic of rising or falling at a certain time constant, as shown in the timing 2 of FIG.
Spike-like error appears when the integrator 15 is reset,
When the rate of change of the input magnetic field is high, there is a problem that an error due to a tracking delay of the fine data as shown in the timing 3 of FIG. 12 appears in the data after the coarse fine synthesis.

The present invention has been made in order to solve the above problems, and eliminates an error in fine data due to a transient characteristic based on a certain time constant during charging / discharging of an integrator in the FLL drive circuit. It aims at realizing more accurate magnetic field measurement.

[0006]

The SQUID type magnetic force measuring apparatus of the present invention has a construction in which a blanking controller is incorporated into the conventional apparatus.

Further, the SQUID type magnetic force measuring device of the present invention has a structure in which the coarse measuring device in the conventional device is replaced with a count type coarse measuring device.

The SQUID type magnetic force measuring device of the present invention is
A slew rate determiner, a coarse data extrapolator, and a selection circuit are incorporated in a conventional device.

[0009]

According to the present invention, when the integrator in the FLL drive circuit is reset by the blanking controller, the voltage output immediately before the reset is held for a certain period of time thereafter, thereby eliminating the spike-like error at the reset time. Achieve more accurate magnetic field measurement.

Further, according to the present invention, when the count type coarse measuring instrument receives the coarse pulse of the FLL drive circuit, the FLL is measured.
Spike-like error at the time of resetting the integrator in the FLL drive circuit is output by outputting the count value as the rough data that reaches a predetermined value with the characteristic that rises with the time constant that determines the transient characteristic at the time of resetting the integrator in the drive circuit. To realize more accurate magnetic field measurement.

According to the present invention, when the slew rate determiner determines that the rate of change of the input magnetic field exceeds a predetermined value, the coarse data extrapolator extrapolates the coarse data and the selection circuit performs A / D conversion.
By changing the output to the converter output and outputting the output of the coarse data extrapolator to the coarse refinement synthesizer, the error due to the tracking delay of the fine data is removed, and more accurate magnetic field measurement is realized.

[0012]

【Example】

Embodiment 1 FIG. Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, 1 to 5 are the same as those in FIG. 7, and 6 is composed of a blanking determination unit 6a and a blanking processing unit 6b. When a coarse pulse is detected by the blanking determination unit 6a, the blanking processing unit 6b This is a blanking controller that holds the output of the coarse-fine synthesizer 5 immediately before the coarse pulse is detected for a time such that the difference between before and after blanking of the data after coarse-fine synthesis is equal to or less than the required value.

The embodiment of the present invention is configured as described above, and since the blanking controller 6 outputs the output of the coarse synthesizer 5 as it is, except when the coarse pulse is generated, the conventional SQU is used.
The ID-type magnetic force measuring device and the processing of the coarse synthesis are the same. When the coarse pulse is generated, this is detected by the blanking controller 6. The blanking controller 6 holds and outputs the output of the coarse-fine synthesizer 5 immediately before the detection of the coarse pulse for a preset fixed time. Here, the fixed time is the FLL drive circuit 2
It is set in consideration of the time constant of the discharge transient characteristic of the internal integrator and the error allowed in the precise data. If the time constant becomes a large value, it takes a long time accordingly.
Therefore, as shown in the timing 4 of FIG. 4, the output after the coarse and fine synthesis becomes a constant value (portion a in the timing 4 of FIG. 4) for the fixed time from the rise of the rough data, and the spike error is removed.

Example 2. In FIG. 2, 1 to 3 and 5 are the same as those in FIG. 7, and 7 is composed of a time constant indicator 7a and a rising counter 7b.
When inputting to b, the count type coarse measuring instrument for referring to the time constant of the discharge transient characteristic of the integrator 15 input to the time constant indicator 7a and outputting the count value of the rising characteristic reaching the predetermined rough data Is.

The embodiment of the present invention is configured as described above, and the processing of the coarse precision synthesis is the same as that of the conventional SQUID type magnetic force measuring apparatus except when the coarse pulse is generated. When a coarse pulse is generated, the count-type coarse measuring instrument 7 is set to the integrator 1 upon detection.
5 has the same rise time characteristic (the portion c in the timing 5 in FIG. 5) as the time constant that determines the discharge transient characteristic (the portion b in the timing 5 in FIG. 5).
A count value reaching a flat portion indicated by d1, d2, and d3 at timing 5 is output to the coarse-fine synthesizer 5 as coarse data. The coarse and fine synthesizer 5 adds the rough data and the fine data as the count value and outputs the result. Therefore, as shown in the timing 5 in FIG. 5, the data after the coarse fine synthesis at the transient characteristic due to the resetting of the integrator 15 is a constant value to which the fine data change indicating the magnetic field change is added. Spike errors due to fine synthesis are removed.

Embodiment 3. In FIG. 3, 1 to 5 are the same as in FIG. 7, 8 is the number of occurrences of the coarse pulse per unit time is monitored, the rate of change of the input magnetic field is determined, and the extrapolation instruction of the coarse data and the selection instruction in the selection circuit 10 are performed. A slew rate determiner for outputting a control signal, 9 determines an approximate straight line connecting the coarse data values at the moment when the coarse data changes based on the control signal of the slew rate determiner 8, and further adjusts to the timing when the coarse data changes, Based on the control signal of the slew rate determiner 8, 10 is a coarse data extrapolator that outputs the coarse data extrapolation output corresponding to the fine data estimated by performing the operation of dropping to the zero point to the fine data at the same rate. It is a selection circuit for selectively outputting either fine data or coarse data extrapolator output.

The embodiment of the present invention is configured as described above, and the change rate of the input magnetic field has a required accuracy due to the error of the fine data (the portion e in the timing 6 in FIG. 6) due to the tracking delay of the FLL drive circuit 2. Below a certain value to be satisfied,
Since the selection circuit 10 outputs precise data, the coarse-fine synthesizer 5
The rough data and the fine data are added and output, and the conventional SQUID type magnetic force measuring device has the same synthesis processing as the coarse data. When the rate of change of the input magnetic field exceeds the predetermined value, the slew rate determiner 8 detects this and the coarse data extrapolator 9
Also, a control signal is output to the selection circuit 10. When the coarse data extrapolator 9 receives the control signal, the coarse data extrapolator 9 obtains the coarse data value (points f1, f2, f3 at the timing 6 in FIG. 6) at the time of the coarse pulse and the rate of change from the time (g at the timing 6 in FIG. The slope of the straight line) is calculated to estimate the change state of the fine data, and the coarse data extrapolator output corresponding to the fine data is output to the selection circuit 10 at the output rate of the fine data. Selection circuit 10
Similarly to 9, when the control signal is received, the data is changed to fine data, and the output of the coarse data extrapolator 9 is selected and output to the coarse fine synthesizer 5. The coarse-fine synthesizer 5 adds the coarse data and the output of the coarse-data extrapolator 9 corresponding to the precise data and outputs the result. Therefore, FIG.
When the input magnetic field changes at a rate of change that cannot follow the precise data as shown in the timing 6 of FIG. The error due to is removed.

[0018]

As described above, according to the present invention, the following effects can be obtained.

According to the present invention, by adding a blanking controller to the conventional SQUID type magnetic force measuring device, it is possible to set the fine synthesis to the timing 4 shown in FIG. 4 and avoid the occurrence of spike-like errors. It is possible to realize more accurate magnetic field measurement.

Further, according to the present invention, by using the count type coarse measuring device as the coarse measuring device, the synthesis of the coarse refinement can be performed at the timing 5 shown in FIG. 5, and the occurrence of the spike-like error can be avoided. More accurate magnetic field measurement can be realized.

According to the present invention, by adding a slew rate determiner, a coarse data extrapolator and a selection circuit, coarse synthesis can be performed at the timing 6 shown in FIG.
It is possible to realize more accurate magnetic field measurement while avoiding an error due to the delay in tracking the precise data associated with the transient characteristic when the integrator is reset inside the drive circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

FIG. 3 is a block diagram showing a third embodiment of the present invention.

FIG. 4 is a diagram showing a timing of crude refined synthesis in Example 1 of the present invention.

FIG. 5 is a diagram showing a timing of crude refined synthesis in Example 2 of the present invention.

FIG. 6 is a diagram showing a timing of crude refined synthesis in Example 3 of the present invention.

FIG. 7 is a block diagram showing a conventional SQUID type magnetic force measuring device.

FIG. 8 is a diagram showing a magnetic field-voltage characteristic of the SQUID sensor.

FIG. 9 is a diagram showing the relationship between the output of the SQUID sensor and the output of the FLL drive circuit.

FIG. 10 is a diagram showing an ideal timing of coarse refinement synthesis.

FIG. 11 is a diagram showing a timing of coarse and fine synthesis in a conventional apparatus.

FIG. 12 is a diagram showing a timing when a tracking delay occurs in the fine data.

FIG. 13 is a block diagram showing a configuration of an FLL drive circuit.

[Explanation of symbols]

1 SQUID sensor, 2 FLL drive circuit, 3 A /
D converter, 4 coarse measurement device, 5 coarse refinement synthesizer, 6 blanking controller, 6a blanking judgment device, 6b blanking processor, 7 count type coarse measuring device, 7a time constant indicator, 7b rising counter, 8 slew rate determiner, 9 coarse data extrapolator, 10 selection circuit, 11 oscillator, 12 feedback coil, 13 resonance circuit,
14 multipliers, 15 integrators.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masakatsu Fujinuma 325 Kamimachiya, Kamakura City Mitsubishi Electric Co., Ltd. Kamakura Factory (72) Inventor Takayuki Inaba 325 Kamimachiya, Kamakura City Mitsubishi Electric Co., Ltd. Kamakura Factory

Claims (3)

[Claims] 1. A SQUID sensor for detecting a magnetic field, and a periodic voltage change corresponding to a change in an input magnetic field of the SQUID sensor is linearly converted and output, and the output is an arbitrary predetermined one of the periodic voltage changes. When a voltage value corresponding to the number of cycles is reached, a FLL driving circuit that resets the voltage value and outputs a coarse pulse, and an A / D converter that converts the voltage output of the FLL driving circuit into digital precise data,
A coarse measuring device that converts the coarse pulse into coarse data obtained by an integral multiple of the magnetic field amount corresponding to the number of cycles and outputs the coarse data, and a coarse fine synthesizer that adds the coarse data and the fine data and outputs the detected magnetic field amount. And a blanking controller which holds the output of the coarse fine synthesizer immediately before the coarse pulse is detected for a certain period of time when the coarse pulse is detected.
Type magnetic force measuring device. 2. A SQUID sensor for detecting a magnetic field, and a periodic voltage change corresponding to a change in an input magnetic field of the SQUID sensor is linearly converted and output, and the output is an arbitrary predetermined one of the periodic voltage changes. When a voltage value corresponding to the number of cycles is reached, a FLL driving circuit that resets the voltage value and outputs a coarse pulse, and an A / D converter that converts the voltage output of the FLL driving circuit into digital precise data,
When the coarse pulse is input, a count type coarse measuring device that outputs a count value that reaches a coarse data obtained by an integral multiple of the magnetic field amount corresponding to the number of cycles based on a predetermined characteristic, the coarse data and the fine data. The SQUID type magnetic force measuring device is characterized by further comprising: 3. A SQUID sensor for detecting a magnetic field, and linearly converting and outputting a periodic voltage change with respect to an input magnetic field change of the SQUID sensor, and the output of the SQUID sensor is an arbitrary predetermined one of the periodic voltage changes. When a voltage value corresponding to the number of cycles is reached, a FLL driving circuit that resets the voltage value and outputs a coarse pulse, and an A / D converter that converts the voltage output of the FLL driving circuit into digital precise data,
A coarse measuring instrument that converts the coarse pulse into coarse data obtained by an integral multiple of the magnetic field amount corresponding to the number of cycles and outputs the coarse data, and a slew rate is determined from the number of times the coarse pulse is generated per unit time, and a control signal is output. A slew rate determiner, and a coarse data extrapolator that outputs a coarse data extrapolation output corresponding to fine data estimated by extrapolation of coarse data based on the control signal of the slew rate determiner to the fine data at the same rate, A selection circuit for selectively outputting either the fine data or the coarse data extrapolator output based on the control signal of the slew rate determiner, and the magnetic field detected by adding the coarse data and the fine data or the coarse data extrapolator output. An SQUID type magnetic force measuring device, comprising: a coarse-fine synthesizer for outputting a quantity.