JPH11148968A - SQUID magnetometer control method and device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce the dynamic range by canceling an offset voltage caused by an environmental magnetic field. SOLUTION: An output voltage from a superconducting ring 3a to which a predetermined bias current is supplied is amplified, integration processing is performed, a feedback signal is generated based on the integration signal, and the feedback signal is supplied to a feedback coil 3b. An analog signal processing circuit 7 that holds a signal for canceling an offset magnetic field by performing signal processing based on an integration signal with respect to a SQUID magnetometer that compensates for a change in external magnetic flux introduced into the superconducting ring 3a, A voltage adder 9 is provided which superimposes this signal on the feedback signal and supplies it to the feedback coil 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling a SQUID magnetometer and an apparatus therefor.
A predetermined bias current is supplied to the superconducting ring by amplifying the output voltage from the superconducting ring, performing integration processing, generating a feedback signal based on the integrated signal, and supplying the feedback signal to the feedback coil. A method and apparatus for controlling a SQUID magnetometer that compensates for changes in external magnetic flux.

[0002]

2. Description of the Related Art Conventionally, SQUIDs using SQUIDs have been proposed.
D magnetometers have been proposed. FIG. 11 shows a conventional SQUID
FIG. 3 is a block diagram illustrating a configuration of a magnetometer. This SQUID
In the magnetometer, the output voltage from the bias signal source 81 is converted into a current signal by a voltage-current converter 82 and S
The QUID 83 is supplied to a superconducting ring 83a including a Josephson junction. Then, the output voltage from the superconducting ring 83a is amplified by the preamplifier 84, further amplified by the amplifier 85, demodulated and integrated by the demodulator / integrator 86, and the integrated signal is subjected to a magnetic flux lock loop (FLL).
Circuit output. The integrated signal and the carrier from the modulation carrier generation source 87 are supplied to a voltage adder 88 to obtain a feedback signal. The feedback signal is converted to a feedback current by a voltage-current converter 89 and supplied to a feedback coil 83b of the SQUID 83. ing. 83c is an input coil, which is connected in series with the pickup coil 83d. The output signal of the FLL circuit is amplified by an amplifier 86a and converted into a digital signal by an A / D converter 86b. Further, the output voltage from the superconducting ring 83a is amplified by the preamplifier 84, further amplified by the amplifier 85, demodulated and integrated by the demodulator / integrator 86, and output from the integrated signal and the modulation carrier wave source 87. The FLL circuit is a circuit that supplies the carrier to the voltage adder 88 to obtain a feedback signal, converts the carrier into a feedback current by the voltage-current converter 89, and supplies the feedback current to the feedback coil 83b of the SQUID 83.

Therefore, a change in environmental magnetic flux detected by the pickup coil 83d and introduced into the superconducting ring 83a by the input coil 83c is canceled by a compensation magnetic flux supplied from the feedback coil 83b to the superconducting ring 83a. The integration signal output from the demodulator / integrator 86 is used as a magnetic flux measurement signal.

[0004]

However, the conventional S
When a QUID magnetometer is employed, an offset voltage caused by an environmental magnetic field is superimposed on the integration signal due to the characteristics of the SQUID driving method, and the dynamic range is significantly reduced. This will be described in more detail.

FIGS. 12A and 12B show V / Φ of SQUID.
It is a figure showing a characteristic. When the V / Φ characteristic of the SQUID at a certain moment is as shown in FIG.
Operating the circuit to fix the magnetic flux, which is the operating principle of the FLL circuit, means that the measured magnetic field is changed to V / in FIG.
As in the case of the Φ characteristic, for example, the valley of the V / Φ characteristic (which may be fixed to the top of the peak) is made to coincide with the measured magnetic field, and is fixed. The V of SQUID is adjusted so that the valley closest to the measured magnetic field (see a in FIG. 12A) matches the position of the measured magnetic field.
It is necessary to shift the / Φ characteristic {see b in FIG. 12A}.

Here, if the measured magnetic field is on the right side of the position shown in FIG.
The position of the valley where the magnetic flux is fixed is not a in FIG. 12A but c in FIG. 12A. Therefore, the range of the magnitude of the phase of the V / Φ characteristic of the SQUID shifted when the magnetic flux is fixed is ± Φ0 / 2 (Φ0 is V / Φ) with respect to the valley.
The period of the Φ characteristic, ie, the magnetic flux quantum).

Now, in order to match the measured magnetic field with the valley by shifting the phase of the V / Φ characteristic, the magnitude of the shift with respect to the feedback coil (see b in FIG. 12A) is equivalent to: It is necessary to generate a magnetic field opposite to the measurement magnetic field. The predetermined current to be passed through the feedback coil to generate this magnetic field is a value obtained by performing voltage-to-current conversion of a predetermined voltage, and this voltage is obtained by measuring the output voltage from the SQUID, The difference between the voltage (actually adjusted to 0 V by performing a process such as passing through a bypass filter) and the voltage determined by the measured magnetic field is amplified and calculated.

If this voltage is directly converted to a magnetic field for shifting the phase, the shift is instantaneously eliminated, and the magnetic field for correcting the shift is also reset. Therefore, the displacement occurs again, and the magnetic flux cannot be fixed. Therefore, the value of the magnetic field for correcting the displacement needs to be maintained after the correction of the displacement. For this reason, the voltage for correcting the deviation calculated from the output signal of the SQUID described above is once taken into the integrator and the value is held. Therefore, by performing this process continuously,
The deviation can always be corrected, and the state where the valley of the V / Φ characteristic of the SQUID matches the position of the measurement magnetic field can be maintained.

By the way, from the viewpoint of the output signal proportional to the measurement magnetic field, the magnetic field generated in the feedback coil in order to make the position of the measurement magnetic field coincide with the valley of the SQUID V / Φ characteristic {FIG. A) b reference in {} is, in other words, V / Φ of the original SQUID.
A valley that can be a lock point in the phase of the characteristic ｛FIG.
(A) of the value of the measured magnetic field viewed with reference
The value obtained by inverting the polarity, that is, the output voltage of the integrator generating the magnetic field is the signal output in proportion to the measured magnetic field.

As can be seen from the above description, the above FL
In the L circuit, a voltage corresponding to a maximum of ± Φ0 / 2 (the voltage value differs depending on the set value of the circuit constant) may be output from the integrator, that is, the FLL circuit as an initial offset, and the circuit constant is changed. As the resolution is increased, the offset voltage is also amplified and increased.

Further, if the SQUID magnetometer is operated in an environment where there is an aperiodic environmental magnetic field drift, the offset voltage may similarly increase sequentially even if the initial offset is small. As a result, the dynamic range decreases as the offset voltage increases.

[0012]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has a method of controlling a SQUID magnetometer capable of canceling an offset voltage caused by an environmental magnetic field and preventing a narrow dynamic range. It is intended to provide a device.

[0013]

According to a first aspect of the present invention, there is provided a method for controlling a SQUID magnetometer which amplifies an output voltage from a superconducting ring to which a predetermined bias current is supplied, performs an integration process, and performs an integration process based on the integration signal. SQ that compensates for changes in the external magnetic flux introduced into the superconducting ring by generating a feedback signal and supplying the feedback signal to the feedback coil
In the UID magnetometer, a method of calculating an offset signal by performing predetermined signal processing with an integral signal as an input, performing offset compensation processing based on the calculated offset signal, and obtaining a magnetic flux detection signal in which the offset signal is canceled. is there.

According to a second aspect of the present invention, there is provided a method for controlling a SQUID magnetometer.
This is a method of achieving offset compensation processing by canceling the offset magnetic flux based on the calculated offset signal. The SQUID magnetometer control method according to a third aspect is a method of achieving an offset compensation process by correcting an integrated signal based on a calculated offset signal.

According to a fourth aspect of the present invention, there is provided a SQUID magnetometer control device,
A predetermined bias current is supplied to the superconducting ring by amplifying the output voltage from the superconducting ring, performing integration processing, generating a feedback signal based on the integrated signal, and supplying the feedback signal to the feedback coil. In a SQUID magnetometer for compensating a change in external magnetic flux, an offset signal calculating means for calculating an offset signal by performing predetermined signal processing with an integrated signal as an input, and performing an offset compensation process based on the calculated offset signal. And an offset compensating means for obtaining a magnetic flux detection signal in which the offset signal is canceled.

A SQUID magnetometer control device according to claim 5 is
As the offset compensating means, one that achieves offset compensation processing by canceling the offset magnetic flux based on the calculated offset signal is employed. In the SQUID magnetometer control device according to a sixth aspect, as the offset compensating means, a magnetic flux for canceling the offset magnetic flux is generated from the feedback coil based on the calculated offset signal, and the generated magnetic flux accomplishes the offset compensation process. It is something that adopts.

According to a seventh aspect of the present invention, there is provided a SQUID magnetometer control device,
As the offset compensating means, a means for generating a magnetic flux for canceling the offset magnetic flux based on the calculated offset signal from the auxiliary coil so as to supply the magnetic flux to the pickup coil and achieving the offset compensation process by the generated magnetic flux is adopted. It is. The SQUI of claim 8
The D magnetometer control device, as the offset compensating means,
The one that achieves offset compensation processing by correcting the integrated signal based on the calculated offset signal is employed.

[0018]

According to the SQUID magnetometer control method of the first aspect, the output voltage from the superconducting ring to which a predetermined bias current is supplied is amplified, and the integration process is performed.
By generating a feedback signal based on the integration signal and supplying the feedback signal to a feedback coil, the SKU is compensated for by compensating for a change in external magnetic flux introduced into the superconducting ring.
When operating the ID magnetometer, an offset signal is calculated by performing a predetermined signal processing with the integrated signal as an input, an offset compensation process is performed based on the calculated offset signal, and a magnetic flux detection that cancels the offset signal is performed. Since the signal is obtained, it is possible to prevent the disadvantage that the dynamic range is narrowed due to the offset signal, thereby improving the magnetic flux measurement sensitivity.

According to the SQUID magnetometer control method of the second aspect, the offset compensation processing is achieved by canceling the offset magnetic flux based on the calculated offset signal.
Offset compensation processing can be performed on the ID side. According to the SQUID magnetometer control method of the third aspect, the offset compensation processing is achieved by correcting the integral signal based on the calculated offset signal. Side can perform the offset compensation processing.

According to the SQUID magnetometer control device of the present invention, an output voltage from a superconducting ring to which a predetermined bias current is supplied is amplified, an integration process is performed, and a feedback signal is generated based on the integration signal. By compensating for changes in external magnetic flux introduced into the superconducting ring by generating and feeding it to the feedback coil, S
In operating the QUID magnetometer, the offset signal is calculated by the offset signal calculating means by performing predetermined signal processing with the integrated signal as an input, and the offset compensating means calculates the offset signal based on the calculated offset signal. By performing the processing, a magnetic flux detection signal in which the offset signal is canceled can be obtained.

Therefore, it is possible to prevent the disadvantage that the dynamic range is narrowed due to the offset signal, thereby improving the magnetic flux measurement sensitivity. According to the SQUID magnetometer control device of claim 5, since the offset compensating means adopts one that achieves offset compensation processing by canceling the offset magnetic flux based on the calculated offset signal. In addition to the effect of 4, the SQUID can perform offset compensation processing.

According to the SQUID magnetometer control device of the present invention, a magnetic flux for canceling the offset magnetic flux is generated from the feedback coil based on the calculated offset signal as the offset compensating means. Since the one that achieves the compensation processing is adopted, the offset compensation processing can be performed on the SQUID side by the feedback coil in addition to the function of claim 4.

According to the SQUID magnetometer control device of the present invention, the offset compensating means generates a magnetic flux for canceling the offset magnetic flux from the auxiliary coil based on the calculated offset signal to supply the magnetic flux to the pickup coil. Since an apparatus that achieves the offset compensation processing by using the generated magnetic flux is adopted, the offset compensation processing can be performed on the SQUID side by the pickup coil in addition to the operation of the fourth aspect.

According to the SQUID magnetometer control device of the present invention, the offset compensating means employs a device which achieves offset compensation processing by correcting an integrated signal based on the calculated offset signal. In addition, in addition to the function of claim 4, offset compensation processing can be performed on the magnetic flux measurement signal output side.

[0025]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a SQUID magnetometer control method and apparatus according to the present invention. FIG. 1 shows the SQUID of the present invention.
It is a block diagram showing one embodiment of a magnetometer control device.

In the SQUID magnetometer control device, the output voltage from the bias signal source 1 is converted into a bias current by the voltage-current converter 2, and the SQUID 3
The power is supplied to a superconducting ring 3a having a Josephson junction. Then, the output voltage of the superconducting ring 3a is amplified by the preamplifier 4, further amplified by the amplifier 5, and supplied to the demodulator / integrator 6. Then, the output signal (FLL circuit output signal) from the demodulator / integrator 6 is supplied to the analog signal processing circuit 7, and the output signal from the analog signal processing circuit 7, the FLL circuit output signal and the modulation carrier generation source 8 are output. Is supplied to the voltage adder 9 to obtain a feedback signal, which is converted into a feedback current by the voltage-current converter 10, and the feedback coil 3b of the SQUID 3
To supply. The FLL circuit output signal is amplified by an amplifier 6a, converted into a digital signal by an A / D converter 6c, and output. Reference numeral 3c denotes an input coil, which is connected in series with the pickup coil 3d, so that a magnetic flux corresponding to the environmental magnetic field detected by the pickup coil 3d is input to the input coil 3c.
Through the superconducting ring 3a.

FIG. 2 is a block diagram showing a configuration of the analog signal processing circuit 7. The low-pass filter 7a receives an output signal of the FLL circuit, an integrator 7b receives an output signal of the low-pass filter 7a, and an integrator. And an inverting buffer 7c to which the output signal of 7b is input. Here, the cut-off frequency of the low-pass filter 7a is preferably set to 1 Hz or less, for example, so as not to affect the frequency of a measurement target (for example, a biomagnetic field such as a magnetocardiogram or a brain magnetic field).

The operation of the SQUID magnetometer control device having the above configuration is as follows. With respect to the superconducting ring 3a to which the bias current is supplied, the pickup coil 3d
When a magnetic flux corresponding to the environmental magnetic field detected by the SQUID 3 is introduced via the input coil 3c, a feedback current is obtained by the FLL circuit and supplied to the feedback coil 3b, so that the valley of the V / Φ characteristic of the SQUID 3 and the measurement magnetic field are measured. And FL as the magnetic flux measurement signal
An L circuit output signal can be output.

Further, the output signal of the FLL circuit is supplied to a low-pass filter 7a to extract only an offset magnetic field and a magnetic field drift (a magnetic field irrelevant to an object to be measured such as a biological magnetic field) caused by an environmental magnetic field. By supplying the extracted offset magnetic field and magnetic field drift to the integrator 7b, a voltage for generating a magnetic field in the feedback coil 3b for correcting a phase shift is held, and the polarity is inverted by the inversion buffer 7c to add the voltage. To the vessel 9. Therefore, the integrator in the FLL circuit does not need to hold the voltage for correcting the offset magnetic field and the magnetic field drift, and only the voltage for which the offset voltage has been canceled based on the output signal from the analog signal processing circuit 7. And the resolution can be increased by amplifying only the signal of the frequency component to be observed.

As is clear from the above description, since the offset voltage is canceled, the dynamic range of the SQUID magnetometer can be used at full scale. This will be described in more detail. As shown in FIG. 3, when a slight offset voltage is superimposed on the FLL circuit output signal, if the FLL circuit output signal is amplified by, for example, an amplifier having an amplification factor of 10 times,
It becomes as shown in the following.
As shown in FIG. That is, when the FLL circuit output signal on which the offset voltage is slightly superimposed is converted into a digital signal and processed, a case is considered in which the signal is amplified by an amplifier in order to increase the resolution of the signal by the A / D converter. Since the offset voltage is also amplified at the same time, the signal component to be extracted is saturated in the dynamic range of the A / D converter (see FIG. 4). In order to prevent this inconvenience, the amplification rate of the
It is necessary to keep the signal within the dynamic range of the D converter (see FIG. 5). However, in this case, the resolution of the A / D converter is reduced, so that it is impossible to analyze a signal with high precision.

On the other hand, the SQUID of the above embodiment
When the D magnetometer control device is employed, since the offset voltage is canceled from the FLL circuit output signal as shown in FIG. 6, the FLL circuit output signal is amplified by, for example, an amplifier having an amplification factor of 10 times. In addition, as shown in FIG. 7, the inconvenience that the signal to be extracted is saturated in the dynamic range of the A / D converter does not occur.
The dynamic range of the D converter can be used without waste, and more precise signal analysis can be achieved.

FIG. 8 is a block diagram showing another embodiment of the SQUID magnetometer control device of the present invention. This SKU
The difference between the ID magnetometer control device and the SQUID magnetometer control device of FIG. 1 is that a digital signal processing circuit 7 ′ is used instead of the analog signal processing circuit 7 and an analog signal is input to the input side of the digital signal processing circuit 7 ′. -Digital converter 7
d is connected to a digital-analog converter 7e on the output side.

Therefore, when the SQUID magnetometer control device of this embodiment is adopted, the process of holding the voltage for correcting the offset magnetic field and the magnetic field drift can be digitized outside the FLL circuit. 1, the same operation as the embodiment of FIG. 1 can be achieved. FIG. 9 is a block diagram showing still another embodiment of the SQUID magnetometer control device of the present invention.

This SQUID magnetometer control device corresponds to the SQUID magnetometer shown in FIG.
The difference from the QUID magnetometer controller is that only the output signal of the demodulator / integrator 6 and the output signal of the modulation carrier generation source 8 are supplied to the voltage adder 9, and the output signal of the demodulator / integrator 6 is Only at the point where the signal is supplied to the analog signal processing circuit 7, the output signal of the analog signal processing circuit 7 is converted into a current signal by the voltage-current converter 11, and is supplied to the auxiliary coil 12 magnetically coupled to the pickup coil 3d. It is.

When this embodiment is adopted, the voltage for correcting the offset magnetic field and the magnetic field drift is set to F
The signal is held in the analog signal processing circuit 7 outside the LL circuit, converted into a current, and supplied to the auxiliary coil 12, so that the current does not pass through the feedback coil 3b but the auxiliary coil 12
To the superconducting ring 3a through the pickup coil 3d and the input coil 3c, and the same operation as the embodiment of FIG. 1 can be achieved.

FIG. 10 is a block diagram showing still another embodiment of the SQUID magnetometer control device of the present invention. This SQUID magnetometer control device differs from the SQUID magnetometer control device of FIG. 1 in that only the output signal of the demodulator / integrator 6 and the output signal of the modulation carrier generation source 8 are supplied to the voltage adder 9. The output signal of the demodulator / integrator 6 is supplied to the analog signal processing circuit 7, and the output signal of the analog signal processing circuit 7 and the output signal of the demodulator / integrator 6 are supplied to the voltage adder 13 to output the FLL circuit output. The only point to gain.

When this embodiment is adopted, the voltage for correcting the offset magnetic field and the magnetic field drift is changed to F
The voltage is held in an analog signal processing circuit 7 outside the LL circuit, and the held voltage and an output signal of the demodulator / integrator 6 are added to a voltage adder 1.
By adding to 3, it is possible to obtain an FLL circuit output excluding the effects of the offset magnetic field and the magnetic field drift.

Therefore, the integrator in the FLL circuit holds the voltage for correcting the offset magnetic field and the magnetic field drift, but the output signal of the voltage adder 13 is based on the output signal from the analog processing circuit 7. Becomes a voltage in which the offset voltage is canceled, and the resolution can be increased by amplifying only the signal of the frequency component to be observed in the subsequent stage.

As is clear from the above description, since the offset voltage is canceled, the dynamic range of the SQUID magnetometer can be used at full scale. In the embodiments of FIGS. 9 and 10,
It is possible to use a digital signal processing circuit 7 'instead of the analog signal processing circuit 7.

[0040]

According to the first aspect of the present invention, it is possible to prevent the disadvantage that the dynamic range is narrowed due to the offset signal, and to achieve a specific effect that the magnetic flux measurement sensitivity can be enhanced. The invention of claim 2 has a specific effect that the offset compensation processing can be performed on the SQUID side in addition to the effect of claim 1.

The third aspect of the invention has a special effect that the offset compensation processing can be performed on the magnetic flux measurement signal output side in addition to the effect of the first aspect. Claim 4
The invention of (1) has a unique effect that the disadvantage that the dynamic range is narrowed due to the offset signal is prevented from occurring, and the magnetic flux measurement sensitivity can be enhanced.

According to the fifth aspect of the present invention, in addition to the effect of the fourth aspect, there is a special effect that the SQUID side can perform the offset compensation processing. According to the invention of claim 6, in addition to the effect of claim 4, a unique effect that the feedback compensation coil can perform offset compensation processing on the SQUID side is achieved.

According to the seventh aspect of the present invention, in addition to the effect of the fourth aspect, a unique effect that the pickup coil can perform the offset compensation processing on the SQUID side. The invention of claim 8 provides the effect of claim 4,
There is a unique effect that the offset compensation processing can be performed on the magnetic flux measurement signal output side.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a SQUID magnetometer control device of the present invention.

FIG. 2 is a block diagram illustrating a configuration of an analog signal processing circuit.

FIG. 3 is a diagram illustrating an example of an FLL circuit output signal on which an offset voltage is superimposed.

FIG. 4 is a diagram showing a signal obtained by amplifying the output signal of the FLL circuit of FIG. 3 by an amplifier having an amplification factor of 10;

5 is a diagram showing a signal obtained by amplifying the output signal of the FLL circuit of FIG. 3 by an amplifier having an amplification factor of 6;

FIG. 6 is a diagram illustrating an example of an FLL circuit output signal from which an offset voltage has been removed.

7 is a diagram showing a signal obtained by amplifying the output signal of the FLL circuit of FIG. 6 by an amplifier having an amplification factor of 10;

FIG. 8 is a block diagram showing another embodiment of the SQUID magnetometer control device of the present invention.

FIG. 9 is a block diagram showing still another embodiment of the SQUID magnetometer control device of the present invention.

FIG. 10 is a block diagram showing still another embodiment of the SQUID magnetometer control device of the present invention.

FIG. 11 is a block diagram showing a configuration of a conventional SQUID magnetometer.

FIG. 12 is an SQ for explaining the operation principle of the FLL circuit;
FIG. 4 is a V / Φ characteristic diagram of a UID.

[Explanation of symbols]

3a Superconducting ring 3b Feedback coil 3d Pickup coil 7 Analog signal processing circuit 7 'Digital signal processing circuit 9 Voltage adder 12 Auxiliary coil 13 Voltage adder

Claims (8)

[Claims] 1. A feedback coil (3b) that amplifies an output voltage from a superconducting ring (3a) to which a predetermined bias current is supplied, performs an integration process, generates a feedback signal based on the integration signal, and generates a feedback signal. In the SQUID magnetometer for compensating for the change in the external magnetic flux introduced into the superconducting ring (3a) by supplying the integrated signal to the superconducting ring (3a), the integrated signal is input and a predetermined signal processing is performed to calculate an offset signal. And performing offset compensation processing based on the signal to obtain a magnetic flux detection signal in which the offset signal is canceled.
ID magnetometer control method. 2. The SQUID magnetometer control method according to claim 1, wherein offset compensation processing is achieved by canceling the offset magnetic flux based on the calculated offset signal. 3. The SQUID magnetometer control method according to claim 1, wherein the offset compensation processing is achieved by correcting the integrated signal based on the calculated offset signal. 4. A feedback coil (3b) that amplifies an output voltage from a superconducting ring (3a) to which a predetermined bias current is supplied, performs an integration process, generates a feedback signal based on the integration signal, and generates a feedback signal. In the SQUID magnetometer for compensating the change in the external magnetic flux introduced into the superconducting ring (3a) by supplying the integrated signal to the superconducting ring (3a), an offset signal is calculated by performing a predetermined signal processing with the integrated signal as an input. 7)
(7 ') and offset compensating means (9) (1) for performing offset compensation processing based on the calculated offset signal to obtain a magnetic flux detection signal in which the offset signal is canceled.
2) A SQUID magnetometer control device comprising (13). 5. The offset compensating means (9) (12).
5. The SQUID magnetometer control device according to claim 4, wherein the offset compensation processing is achieved by canceling the offset magnetic flux based on the calculated offset signal. 6. The feedback coil (3b), wherein the offset compensating means (9) transmits a magnetic flux for canceling the offset magnetic flux based on the calculated offset signal.
6. The SQUID magnetometer control device according to claim 5, wherein offset compensation processing is achieved by the generated magnetic flux. 7. The offset compensating means (12) generates a magnetic flux for canceling an offset magnetic flux based on the calculated offset signal by a pickup coil (3d).
6. The SQUID magnetometer control device according to claim 5, wherein the magnetic flux is generated from an auxiliary coil (12) so as to be supplied to the SQUID, and an offset compensation process is achieved by the generated magnetic flux. 8. The SQUID magnetometer control device according to claim 4, wherein said offset compensating means (13) achieves offset compensation processing by correcting an integrated signal based on the calculated offset signal.