Fast Thermocouples as Control-System Elements Sensing Exhaust-Gas Temperatures in Aircraft Gas Turbines

Factors which favor the use of thermocouples as control-system elements sensing exhaust-gas temperatures in aviation gas turbines are presented, as well as the development of a construction having adequate strength to withstand vibration. The authors give analytical and experimental determinations of the time constant of thermocouples and present a mathematical analysis of the effect on time constant of conduction along the thermocouple wire to the support. The paper also includes a discussion of the recovery factors of thermocouples and an evaluation of the error introduced when a number of thermocouples that read different temperatures are connected in parallel.