HYSTERESIS CHARACTERISTIC TYPE DIGITAL FLL APPARATUS USING SQUID COUNTER SYSTEM

摘要

In a SQUID fluxmeter, a high resolution, a high throughput and a high dynamic range are achieved without using any expensive circuit components exhibiting large numbers of processed bits and capable of performing high-rates processings. A digital FLL circuit using a double counter system utilizes two or more counters: a change quantity counter (37) in a digital FLL for performing a high-rate processing; and a reproduction counter (53) in a control/measurement computer. Additionally, a hysteresis characteristic having 1φ0 plus margin is used. That is, a counter is used to count the changes of the magnetic flux status, and during these changes, the control is stabilized by controlling the magnetic flux such that it goes along different paths between a case in which the magnetic flux increases and a case in which the magnetic flux decreases.