Direct-reading magnetic flux modulation reading circuit and method

Abstract

The invention provides a direct-reading magnetic flux modulation reading circuit and method. The reading circuit comprises a SQUID device, a pre-amplifier for amplifying the output signal of the SQUID device, a high-pass filter for filtering a DC component and low-frequency noise, a modulation/demodulation signal generator, a demodulator for demodulating the output signal of the high-pass filter, an integrator for carrying out integration and generating a response voltage signal, and a feedback module for feeding back the response voltage signal to the SQUID device. Through modulation, the working point of the SQUID device is allowed to be switched between two working points, and the change trends of the two working points are opposite; and the measured signal is subjected to amplification, high-pass filtering, demodulation and integration, and then, is fed back to the SQUID device, so that the working point is locked. Isolation of the low-frequency noise and the output DC bias of the pre-amplifier is realized through the high-pass filter; the SQUID magnetic flux-voltage conversion coefficient does not reduce due to the load effect; higher harmonic distortion does not occur to a SQUID magnetic flux-voltage curve; the problem of thermal noise of a transformer is prevented; and the circuit is simpler in structure and higher in practicality.

Description

technical field [0001] The invention relates to the technical field of magnetic sensors, in particular to a direct-reading magnetic flux modulation readout circuit and method. Background technique [0002] A superconducting quantum interference device (Superconducting Quantum Interference Device, SQUID) is a highly sensitive magnetically sensitive device that can be used to construct a superconducting magnetic sensor. It is widely used in weak magnetic field detection applications such as biological magnetic field, earth magnetic field anomaly, extremely low field nuclear magnetic resonance and geophysical exploration, and its detection sensitivity has reached Feite (10 -15 Tesla) magnitude. SQUID magnetic sensor is an important magnetic sensor device in limit detection and scientific research, and has high scientific research and application value. [0003] In actual application, SQUID mostly works in the low frequency band (less than 10Hz), and the low frequency noise pe...

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Problems solved by technology

[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a direct-reading magnetic flux modulation readout circuit and method for solving thermal noise, signal amplitude reduction, at the working point problems such as getting smaller

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