Magnetometers using two amorphous core muitivibrator bridge

Accurate and quick-response type magnetometers are presented using two-amorphous-core multivibrator bridge with a dc output. As-prepared zero-magnetostrictive amorphous ribbons of Fe4.7Co70.3B15Si10with 1 mm width are used in straight form for sensing of absolute value of fields or field difference. In these two-core type magnetometers, sensitivity is about eight times that of one-core type magnetometers and the minimum detectable field is about 10^-5Oe. Temperature stability and flux change stability are high due to that the flux reversals occur in mainly rotational magnetization regions, in which Barkhausen noises and iron losses are low and aging of flux changes is very small. The maximum frequency or cut-off frequency of detected sinusoidal fields is as high as about 4 kHz which is about four times that in Supermalloy core flux gate magnetometers. The two-core type magnetometers are useful for applications to non-contact type dc and ac current sensors, motor leakage flux sensors, and dynamic displacement sensors for medical electronics, because that only effective field signals are accurately detected by cancelling uniform magnetic disturbances in the two cores.