Pyroelectric Heat-Transfer Sensors for Hypersonic Impulse Facilities

The results obtained in recent tests conducted to compare the performance of pyroelectric heat-transfer sensors to that of thin-skin thermocouple heat-transfer sensors are presented. These results show that under conditions of clean flow and low heating rates there is excellent agreement between the two types of sensors. In a severe environment such as small particles in the flow and high heating rates, the results agree less closely. Techniques to reduce the difference between the heat-transfer rates indicated by the sensors when operating in a severe environment are presented. Installation and calibration procedures for the pyroelectric sensors are discussed. A relative performance comparison of the pyroelectric, thin-skin thermocouple, and platinum resistance thermometer heat-transfer sensors shows that the pyroelectric sensor is superior to the others in sensitivity, minimum size, and ease of data reduction and that it is comparable in durability, accuracy, and vibration susceptibility. The comparison shows the limitations of the pyroelectric sensors include a need for a dynamic calibration, limited operating temperature range, and short test times.