JPH04340488A - Highly-sensitive apparatus for detecting magnetic field - Google Patents

Abstract

PURPOSE:To enable automatic regulation of a bias current and a modulation current in a highly-sensitive apparatus for detecting a magnetic field. CONSTITUTION:A bias current circuit 8 and a modulation current circuit 9 constituting a part of an F.L.L. circuit device of a highly-sensitive apparatus for detecting a magnetic field are provided with a bias signal regulating means 30 and a modulation signal regulating means 31 respectively. An automatic regulation means 24 connected to these bias signal regulating means 30 and modulation signal regulating means 31 and to the output of an amplifier circuit 2 amplifying a signal from DC SQUID 1 or further to the output of a phase detecting circuit 3 detecting an output of the amplifier circuit 2 is provided.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a DC-driven superconducting quantum interference device (DS Superconducting quantum interference device).
Quantum Interference D
The present invention relates to a high-sensitivity magnetic field detection device that measures magnetic flux using a ivice (hereinafter referred to as DCSQUID).

0002

2. Description of the Related Art FIG. 2 is a block diagram showing the configuration of a conventional high-sensitivity magnetic field detection device. The reference signal output from the oscillation circuit 5 is adjusted by the amplitude adjustment circuit 41, converted into a current by the first voltage-current conversion circuit 6, and added to the DC SQUID 1 as a modulation signal. D.C.S.
When an appropriate bias current is supplied to the QUID 1 from the variable current source 40, the magnetic flux interlinking with the DC SQUID 1 is modulated by the modulation signal, detected as a modulation signal, amplified by the amplifier circuit 2, and output from the oscillation circuit 5. It is detected by the phase detection circuit 3 using the reference signal. A detection signal corresponding to the output of the phase detection circuit 3 is output from the integration circuit 4, converted into a current by the second voltage-current conversion circuit 7, and fed back to compensate for changes in the magnetic flux interlinked with the DC SQUID 1. As a signal, DC SQUID1
added to. The magnetic field can then be measured by reading out this feedback signal or detection signal. Measurements of minute magnetic fields are performed under a special environment that is magnetically shielded to remove disturbance magnetic fields. Conventionally, the adjustment of the variable current source 40 and the amplitude adjustment circuit 41 for performing the above-mentioned measurements has been carried out in an environment with a disturbance magnetic field, or by adding noise to the DC SQUID 1 using a magnetic material such as a magnet, and performing amplification. This was done manually, using something like a variable resistor, while observing the amplitude of the output from circuit 2 synchronized with the reference signal and the output of phase detection circuit 3.

0003

[Problems to be Solved by the Invention] In conventional high-sensitivity magnetic field detection devices, as described above, the bias current and modulation signal are manually adjusted, so it is necessary to bring the equipment necessary for adjustment into the measurement environment. Alternatively, adjustments were made by taking the highly sensitive magnetic field detection device outside the measurement environment. For this reason, even if it is optimally adjusted, it may deviate from the optimal state when measuring in a different environment. In addition, when a highly sensitive magnetic field detection device is put into practical use, a plurality of elements are generally assembled to form multiple channels to measure the spatial distribution of the magnetic field. However, if you were adjusting it manually as above,
There has been a problem in that as the number of channels increases, rapid measurement becomes more difficult.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides F. L. L
．． A bias signal adjustment means and a modulation signal adjustment means are respectively provided in the bias current circuit and the modulation current circuit constituting a part of the circuit device, and the bias signal adjustment means and the modulation signal adjustment means and the DC
The output of the amplifier circuit that amplifies the signal from the SQUID,
Alternatively, automatic adjustment means is further provided which is connected to the output of the phase detection circuit for detecting the output of the amplifier circuit.

[0005]

[Operation] In the high-sensitivity magnetic field measurement device configured as described above, the bias signal adjustment circuit and the modulation signal adjustment circuit are adjusted while the output of the amplifier circuit or the output of the phase detection circuit is evaluated by the automatic adjustment means. You can change the values of the bias signal and modulation signal.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a first embodiment of the invention,
FIG. 2 is a block diagram of the configuration of a highly sensitive magnetic field detection device. In FIG. 1, the DC SQUID 1 is composed of a feedback modulation coil 10 and a DC SQUID ring 11, and the feedback modulation coil 10 and the DC SQUID ring 11 are magnetically coupled. The bias current circuit 8 is connected to the first DC power supply 1
2, a bias signal adjustment means 30, and a third voltage-current conversion circuit 14, and further includes a bias signal adjustment means 30.
is composed of a first D/A conversion circuit 13, a first switch 15, and a first variable resistor 16. The DC power supply 12, the first variable resistor 16, and the first switch 15 are such that when the first switch 15 is on the automatic side, the output signal of the first DC power supply 12 is directly output from the first switch 15, and the first When the switch 15 is on the manual side, the output of the first DC power source 12 is adjusted by the first variable resistor 16 and is connected to be output from the first switch 15. The output of the first switch 15 is connected to the first D/A conversion circuit 13 so as to be input as a reference signal during D/A conversion. 1st D
The analog output of the /A conversion circuit 13 is converted into a current by the third voltage-current conversion circuit 14, and the analog output is converted into a current as a bias current.
C SQUID ring 11.

The automatic adjustment means 24 is composed of an output circuit 25, an input circuit 26, a data processing means 27, and a control means 28. Therefore, it is processed and outputted from the output circuit 25. The control means 28 is connected to the output circuit 25, the input circuit 26, and the data processing means 27, and controls their operations. The output of the output circuit 25 is connected to the digital inputs of the first D/A conversion circuit 13 and the second D/A conversion circuit 23 forming part of the modulation current circuit 9. The amplifier circuit 2 is a DC S
The voltage generated in the QUID ring 11 is detected, amplified and outputted, and the output is connected to the phase detection circuit 3 and the input circuit 26.

The modulation current circuit 9 is composed of an oscillation circuit 5, a modulation signal adjustment means 31, and a first voltage-current conversion circuit 6. Furthermore, the modulation signal adjustment means 31 is composed of a second D/A conversion circuit 23 and a first voltage-current conversion circuit 6. 3, the switch 22, the non-inverting amplifier 17, the inverting amplifier 18, and the second
It is composed of a switch 21, a second variable resistor 20, and a second DC power supply 19. The second DC power supply 19, the second variable resistor 20, and the second switch 21
1 is on the automatic side, the output signal of the second DC power supply 19 is output as is from the second switch 21, and the second switch 2
1 is connected to the manual side so that the output of the second DC power source 19 is adjusted by the second variable resistor 20 and output from the second switch 21. The output of the second switch 21 is
It is connected to the input of the non-inverting amplifier 17 and the input of the inverting amplifier 18. The frequency reference signal output from the oscillation circuit 5 is the third
The output of the non-inverting amplifier 17 and the output of the inverting amplifier 18 are switched at the frequency of the frequency reference signal, and the second D/A is used as the reference signal during D/A conversion. The signal is input to the A conversion circuit 23. The analog output of the second D/A conversion circuit 23 is
It is converted into a current by the voltage-current conversion circuit 6, and is input to the feedback modulation coil 10 as a modulation signal. The output of the amplifier circuit 2 is detected by the phase detection circuit 3 using the reference signal from the oscillation circuit 5, and is input to the integration circuit 4 through the fourth switch 29. The output of the integrating circuit 4 is converted into a current by the second voltage-current conversion circuit 7, and inputted to the feedback modulation coil 10 as a feedback signal.

[0009] In the above configuration, the operation during automatic adjustment will be explained. The output of the amplifier circuit 2 is input to the data processing means 27 through the input circuit 26 in accordance with an input request signal from the control means 28. Data processing means 2
7, in accordance with the command from the control means 28, the amplified signal is analyzed and a digital code that determines the magnitude of the bias signal and modulation signal is sent through the output circuit 25 so that the detection sensitivity of the magnetic field of the DC SQUID 1 is optimized. It is supplied to the digital inputs of the first D/A conversion circuit 13 and the second D/A conversion circuit 23. Then, as mentioned above, the optimal bias signal and modulation signal are
It becomes possible to supply to DC SQUID1.

0010

[Effects of the Invention] According to the above configuration, bias signals and modulation signals can be automatically adjusted in the same environment as the measurement path without using other measurement equipment such as an oscilloscope. can. Further, even when increasing the number of channels, adjustment is easy and quick measurements can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a first embodiment of a highly sensitive magnetic field detection device according to the present invention.

FIG. 2 is a block diagram showing the configuration of a conventional high-sensitivity magnetic field detection device.

[Explanation of symbols]

1 DC SQUID 2 Amplifier circuit 3 Phase detection circuit 4 Integral circuit 5 Oscillation circuit 6 First voltage-current conversion circuit 7 Second voltage-current conversion circuit 8 Bias current circuit 9 Modulation current circuit 12 First DC power supply 14 Third voltage-current conversion circuit 25 Output circuit 26 Input circuit 27 Data processing means 28 Control means 30 Bias signal adjustment means

Claims (1)

[Claims] [Claim 1] Direct current driven superconducting quantum interference device (DC
SQUID) and an F.SQUID for driving this DC SQUID. L. L. (Flux LockedLo
op) A high-sensitivity magnetic field detection device comprising a circuit device, wherein the F.op. L. L. The circuit includes a bias current circuit consisting of a DC power supply, bias signal adjustment means, and a voltage-current conversion circuit;
a modulation current circuit comprising an oscillation circuit, a modulation signal adjustment means, and a voltage-current conversion circuit; an output circuit connected to the bias signal adjustment means and the modulation signal adjustment means; and an amplifier circuit that amplifies the output of the DS SQUID. a phase detection circuit connected to the amplifier circuit; an input circuit receiving at least one of the output signal of the amplifier circuit and the detection signal of the phase detection circuit; and data connected to the output circuit and the input circuit. A high-sensitivity magnetic field detection device comprising processing means, and control means connected to the data processing means, the output circuit, and the input circuit.