MAGNETORESISTIVE POSITION SENSOR FOR CRYOGENIC SPACE APPLICATIONS

摘要

A sensor for detection of angular and linear position in the cryovacuum has been developed. The encoder scheme comprises four magnetoresistors biased by the collimated field of a moving magnet arranged in a closed magnetic circuit. The pairs of mutually variable magnetoresistors are connected in an electrical bridge circuit. Sensor readout via DC measurement avoids electromagnetic interference and allows low pass filtering for high precision measurements of up to 18 Bit resolution. In addition, the device features a large bandwidth for sensing rapid movements in the kHz range. Electromagnetic finite element simulations have been conducted in order to optimize the static and dynamical system performance. Test results are presented, demonstrating high angular resolution of ～ 1.5 arcsec together with low power dissipation ～ 150 μW over a wide operating temperature range (2 K - 300 K). Such a sensor will be applied in the focal plane chopper of the PACS instrument aboard ESAs HERSCHEL Infrared Space Telescope, meeting the stringent requirements regarding cryovibration and thermal cycling. The overall performance and compact dimensions suit the sensor principle for many applications in the field of cry-omechanics.