A linear direct reading thermometer using thermocouples
Drahoslav Barančok, Ilja Thurzo, S Lanyi · Journal of Physics E Scientific Instruments · 1972
A simple resistance network is described by means of which a voltage variation in the form u( phi )=k phi +l phi 2 -m phi 3 (k, l, m>or=0) can be produced through linear variation of minimal number of resistors. The above function is a suitable approximation of the temperature-EMF relation of copper-constantan thermocouples in the temperature range 0 to -190 degrees C. The circuit can be used as a potentiometer which in combination with a copper-constantan thermocouple gives a linear direct-reading thermometer. It may be applied with greater advantage as a source of reference voltage for linear heating or cooling by means of a temperature controller employing a thermocouple. The possibility of using a simpler quadratic approximation and the corresponding network are discussed.