Applications and limitations of thermocouples for measuring temperatures

THE increasing application of temperature measurements to central station control arises primarily from the fact that the limiting factor of safe operation is temperature rather than current or energy output. Another and closely related factor is that of efficiency. With these two influences bearing upon the management there is demanded a knowledge of temperature conditions in the boiler, the engine, the generator and the distributing system. Hence the wide range of temperatures to be measured and the varying circumstances under which they are made often place them beyond the capacity of mercurial or other expansion types of thermometers. Moreover, a permanent and continuous record of temperature may be necessary or it may be desirable to automatically control or limit the temperature of some apparatus or process. The thermocouple has definitely established itself as a convenient and precise instrument for such purposes. We wish, therefore, to consider some of the difficulties to be overcome and precautions to be taken in applying the thermocouple to such measurements.