A high-stability air temperature control system

A multiloop control system has been implemented in a relatively large recirculating air chamber that maintains one-sigma air temperature stability of 3 mK at the outer loop control point. The control system is a modification to a chamber that formerly held air temperature stability of approximately 0.1°C. A continuously running refrigeration system removes the nominal heat load from the air through a cross-flow heat exchanger. The control system maintains temperature stability in the chamber by modulating the power input to a coil heater. Four thermistors in DC bridges are used to generate the feedback signals.