Thermoelectric Temperature Control of Instrumentation -- A Sample Design

Current technology has produced high-performance semiconductor thermoelectric modules that can be a design option for temperature control of electronics and instrumentation. It seems reasonable that their advantages would be helpful to electronics and process control designers who may not be aware of the tremendous advances in the state-of-the-art of thermoelectrics. When dc current is available, thermoelectrics can be used for active bimodal control. This paper describes their fundamental operation, derives some performance relationships, and presents computation techniques for their integration into a system. An example is given where thermoelectrics were used to temperature control the SIMS II Strapdown Inertial Navigator designed by the Charles Stark Draper Laboratory. Test results showed that temperature control of the gyros and accelerometers was achieved to ±0.1°F in ambients between -20°F and 120°F. A worst hot-case coefficient of performance of 0.56 was measured where a 240-watt load at 79°F was moved across a 50°F gradient using 425 watts of thermoelectric power.