A temperature indicator tester
Dartrey Lewis · Journal of Scientific Instruments · 1924
An instrument is described which provides a simple and rapid method of checking the accuracy of temperature indicators or recorders in use with thermocouples. It is shown theoretically that the instrument is electrically equivalent to a thermocouple which can be made to generate any required E.M.F. (in millivolt steps) and to have any required resistance between 1.2 and 12.2 ohms. Details are given of how to use the instrument (a) for checking indicators at one or more points on the scale, so that in a works faulty indicators can be withdrawn from use, and (b) for preparing accurate correction curves for indicators taking into account the increase in resistance of the couple with rise in temperature, so that in a research department indicators may be used in conjunction with calibrated couples to measure temperatures with an accuracy of ± 2° C.