Abstract
A direct-current power amplifier has been constructed for use in a temperature controller, in which a light-coupled transistor (electro-optical coupler) incorporated in the amplifier circuit separates the potentiometric null detector from the heater circuit with respect to the electrical potential relative to the ground. This feature gives a wider choice of the grounding points and larger tolerance about the electrical insulation between the thermocouple and heater in the thermostat than is possible with a direct-coupled amplifier. By using a copper-constantan thermocouple as the thermometer, temperature stabilization within 3mK was readily attained at 220K. Application of the apparatus in the adiabatic calorimetry is suggested.
