Device for the Precise Measurement of Small Temperature Changes

Abstract

A device capable of measuring temperature with a precision corresponding to a standard deviation of about 14 microdegrees at room temperature has been designed and constructed. The device employs a thermistor as the temperature‐sensing element in an ac bridge. The bridge imbalance, after being amplified, is detected by two phase‐sensitive detectors phase‐shifted 90° with respect to each other to insure that both the resistive and reactive components of the bridge elements are balanced.