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Two methods for a first order hardware gradiometer using two high temperature superconducting quantum interference devices

 

作者: M. A. Espy,   R. H. Kraus,   E. R. Flynn,   A. Matlashov,  

 

期刊: Review of Scientific Instruments  (AIP Available online 1998)
卷期: Volume 69, issue 1  

页码: 123-129

 

ISSN:0034-6748

 

年代: 1998

 

DOI:10.1063/1.1148524

 

出版商: AIP

 

数据来源: AIP

 

摘要:

Two different systems for noise cancellation (first order gradiometers) have been developed using two similar high temperature superconducting quantum interference devices (SQUIDs). “Analog” gradiometry is accomplished in hardware by either (1) subtracting the signals from the sensor and background SQUIDs at a summing amplifier (parallel technique) or (2) converting the inverted background SQUID signal to a magnetic field at the sensor SQUID (series technique). Balance levels (ability to reject a uniform background magnetic field) achieved are2×103and1×103at 20 Hz for the parallel and series methods, respectively. The balance level as a function of frequency is also presented. The effects which time delays (phase differences) in the two sets of SQUID electronics have on these balance levels are presented and discussed. It is shown that these delays, along with geometrical considerations, are the limiting factor for balance level for any electronic gradiometer system using two (or more) SQUIDs, a very different situation from the case with wire-wound gradiometers. Results using a dipole field to study the performance of both the parallel and series devices functioning as gradiometers in an unshielded laboratory are presented and compared with theory. ©1998 American Institute of Physics.

 

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