Electricity: measuring and testing – Magnetic – Magnetometers
Patent
1990-08-10
1992-03-10
Wieder, Kenneth A.
Electricity: measuring and testing
Magnetic
Magnetometers
505846, G01R 33035
Patent
active
050952706
ABSTRACT:
A method of suppressing current distribution noise in a DC SQUID comprising two Josephson junctions (12) in a superconducting current. This current distribution noise is caused by individual fluctuations of the critical currents of the two Josephson junctions used for measuring weak magnetic fields. A DC SQUID is connected to a device which comprises a control device (14) for generating a periodic bias current (I.sub.b), a modulation device (15) for generating a flux modulation via an induced AC current in the loop (11), and a signal detection device (17) for forming a mean output voltage (V.sub.ges). The polarity of the bias current (I.sub.B) is reversed by the control device (14) with the modulation frequency and a time shift of one quarter of the period duration of the modulation frequency, so that the SQUID assumes different bias states. In the case of suitably weighted signal detection in the signal detection device (17), the current distribution noise signals stemming from fluctuations of the critical currents eliminate one another in the signal sum taken over four bias states.
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Edmonds Warren S.
Squire William
U.S. Philips Corporation
Wieder Kenneth A.
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