Michal Malátek

Double-core GMI current sensor

A novel design of the giant magnetoimpedance contactless current sensor is presented. A double-core structure is used in order to improve the temperature stability. The temperature coefficient of sensitivity and offset drift are reduced to one-half compared to the single-core sensor. The linearity error decreases by a factor of three. Further utilization of an ac biasing (up to 200 Hz) of the double-core sensor suppresses the temperature offset drift by a factor of 30 (down to 0.6 mA/K) and increases the open-loop linearity to 0.5% for the 2-A range.

Single-core Giant Magnetoimpedance with AC Bias

Enormous improvement of the temperature stability of simple giant magnetoimpedance (GMI) sensor has been reached by means of AC bias of the sensor. Despite of reduction of the frequency range of the sensor to less than 50 Hz, the 100 Hz-current flowing through the bias coil improves the temperature offset stability by the factor of 19; from 1053 nT/K to 54 nT/K (sinewave excitation current of 10 mARMS was used). The offset drift was furthermore reduced to less than 16 nT/K by increasing the amplitude of the excitation current to 24 mARMS.

Inverse Wiedemann Effect Sensor with Pulse Excitation

Recently, a new type of inverse Wiedemann effect (IWE) field sensor with combination of sinewave and DC current excitation was presented. In this paper, the investigation on the sensor driven by unipolar pulses is reported. The sensor was excited by pulses of 40 to 60 mAp with duration from 1 to 5 mus. The best sensitivity and linearity of the sensor were obtained for the pulses with the highest DC component. Additional improvement of the sensitivity was reached by tuning the pick-up coil by parallel capacitor. It has been also proven that controlled integration is more favorable detection technique for the pulse excitation than synchronous demodulation.