Electrolytic resistors for direct-current applications in measuring temperatures
D. Craig · Journal of research of the National Bureau of Standards · 1938
An improved electrolytic resistor, developed primarily for temperature indicators on radio meteorographs, is described.On such instruments variable unidirectional currents are employed.Resistors to be used successfully in such applications require (1) large temperature coefficient, (2) low freezing point, (3) light weight, (4) reversibility, (5) stability of calibration, (6) hermetical sealing, (7) high resistance with minimum inductance and capacitance, and (8) rapid response to temperature changes.The resistor consists of copper electrodes in a capillary tube filled with a solution of cuprous chloride, hydrochloric acid, and ethyl ' alcohol.Various proportions may be used in obtaining solutions which will not freeze at -75 0 C. The alcohol affords a convenient means of adjusting the resistance of a particular resistor to the desired value.Within reasonable limits of impressed voltage, the resistors have been found reliable over a temperature range of +30 0 to -75 0 C.They respond satisfactorily to changes in temperature and hold their calibration for periods of time much in excess of that required for a flight.Ratios of the resistances R tlUo measured with direct current agree with those measured with alternating current.Temperature indications are believed to be accurate within 1 0 C, even at the lowest temperature.