Response of oscillation-controlled magnetic sensing

Abstract

In the oscillation-controlled magnetic sensing system, the dependence of the response on the gain of the feedback loop and the oscillation frequency is investigated. Two types of response were observed according to the gain of the feedback loop. In the first response type, referred to herein as type A, the oscillation starts when the oscillation condition is satisfied and stops when the oscillation condition is not satisfied. In the second response type, referred to herein as type B, when the magnetic field changes, the oscillation starts and then stops because the oscillation condition was at the limit of being fulfilled. For an oscillation frequency of 31MHz, the rise time tR and the fall time tF were 179ns and 1.27μs, respectively, for the type-B response. These times were approximately 1∕10 of those observed for the type-A response. The linearity of the oscillation frequency and the response time in both logarithms was observed for the type-B response, and the rise time tR and fall time tF were reduced as the oscillation frequency was increased.