Use of an Alternating Current Bridge in Laboratory Temperature Control

Abstract

An alternating current bridge and amplifier for continuous temperature control of furnaces and thermostats is described. The circuit is simple and portable and can be made from standard electrical equipment. The power output of the control circuit is doubled for a change of 0.03 percent in resistance of the regulating thermometer. Regulated power up to 500 watts may be obtained. The control circuit has been used to maintain the temperatures of an oil bath and a furnace constant within 0.03°C per hour.