This SAE Aerospace Information Report (AIR) reviews the precautions that must be taken and the corrections which must be evaluated and applied if the experimental error in measuring the temperature of a hot gas stream with a thermocouple is to be kept to a practicable minimum. Discussions will focus on Type K thermocouples. These are defined in NBS Monograph 125 as nickel-chromium alloy versus nickel-aluminum alloy thermocouples.

Purpose:

The purpose of this document is to assist those concerned with measuring gas temperatures in turbines and those who wish to utilize gas temperature for actuating engine controls. In these applications, the problem of temperature measurement may be considered to consist of two distinct parts; namely, a determination of the actual temperature of the measuring junction and a reliable estimation of the difference in temperature between this junction and the gas. The former requires that numerous precautions be observed in the construction, installation, and use of the thermocouple: the latter requires proper application of appropriate corrections for such effects as impact and heat exchange by conduction, convection, and radiation.