Improvement of a Two-Thermocouple Probe Technique for Fluctuating Temperature Measurement

The reliability of a two-thermocouple probe, which is composed of two fine-wire thermocouples of unequal diameters and provides a technique for estimating thermocouple time constants without any dynamic calibration, is appraised in a turbulent wake of a heated cylinder. A reference temperature was obtained simultaneously using a fine-wire resistive thermometer (cold-wire) with a fast response. A comparison between the cold-wire measurement and the compensated thermocouple ones shows that a previous scheme underestimate the thermocouple time constants, unless the noise in the thermocouple signals is negligible and/or the spatial resolution of the probe is sufficiently high. The scheme is improved so as to maximize the correlation coefficient between the two compensated thermocouple outputs, and it offers better compensation of the thermocouple response.