High precision, rapid readout of cryogenic temperature sensors in the Space Shuttle environment

A compact and rugged system designed to perform four-wire determination of the resistance of germanium resistance thermometers (GRT) near 1 K to one part in 65000 in 1 s using 20-nW excitation is described. Constraints unique to cryogenic aerospace systems are addressed. A microcomputer-controlled, hybrid analog/digital design is presented. Test results are presented, and future developments are discussed.<
>