Germanium Resistance Thermometers (CRT) are used to measure the temperature in cryogenic systems in the range of a few tenths of a degree kelvin to about 40 kelvin. For the Lambda Point Experiment (LPE) and Confined Helium Experiment (CHeX) missions, which were flown on the Space Shuttle in 1992 and 1997, respectively, the CRT readout was performed using a digital resistor and an AC bridge technique. Problems encountered with this technique led to the development of a simpler, more robust architecture in which recent developments in analog and digital integrated circuits are used. The sampled DC architecture provides improved long term drift, reduced noise, and elimination of digital resistor contact errors while providing a wide dynamic range. The original motivation for employing the sampled DC architecture was to significantly reduce the board area required by the CRT readout, eliminate the pre-launch tuning requirement, reduce measurement errors, and provide a means for in-flight checkout and calibration. Test results with a temperature stabilized GRT at 4.2K demonstrate a noise of 3.3μK/sqrtHz and a temperature compensated, long term drift of ±0.5μk.
|State||Published - 2001|
|Event||2001 Conference and Exhibit on International Space Station Utilization - Cape Canaveral, FL, United States|
Duration: Oct 15 2001 → Oct 18 2001
|Conference||2001 Conference and Exhibit on International Space Station Utilization|
|City||Cape Canaveral, FL|
|Period||10/15/01 → 10/18/01|