A high frequency platinum resistance thermometer system for measuring turbulent atmospheric temperature fluctuations

A sensor and electronic system has been developed and used to measure high frequency, small scale atmospheric temperature fluctuations. The sensor consists of a platinum wire 0.25 micrometers in diameter and 0.30mm in length. The wire has a time constant of less than 10 microseconds in a 4 m/sec air flow. With a detection current of 50 microamps its sensitivity is 0.063 millevolt/degree C. The electronic system consists of an 80kHz multivibrator, bridge, bridge amplifier, synchronous detector and DC amplifier. The overall system frequency response is flat from DC to 4.5 kHz. The bridge has a noise level of 0.40 microvolts rms and is capable of measuring temperature changes of 0.048C. The overall system noise level varied from 0.18 mv at 10 Hz to 1.6 mv at 1 kHz. Methods are suggested for improving these figures.