Simple bridge detector for use with a low-temperature capacitance thermometer, and thermometer performance limits.
A simple high-resolution bridge circuit for use with a glass-ceramic capacitance thermometer is described. This circuit allows a linear readout of capacitance changes and has better than 1 mK resolution and short-term stability. Performance limits of the thermometer itself are also reported. Irreproducibility of thermometer calibration upon thermal cycling can be as large as 0.3 K, and changes in the calibration slope dC/dT are also observed. The bridge circuit described partially compensates for these shifts in dC/dT.
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Gordon McKay Laboratory and Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.