
thermal contact is poor or, worse, varies during operation, the results you get
may be a poor representation of the actual conditions.
Coolers
A solid-state (Peltier) cooler consists of a series of PN junctions, usually fabricated
from bismuth telluride, that can draw heat from one side and exhaust heat on the
other side. A Peltier cooler can be controlled much like a heater, using a ther-
mistor to measure the temperature. PWM can be used, although to avoid thermal
stress on the semiconductor elements, a minimum PWM frequency is usually
recommended. The minimum is typically around 2 kHz.
One concern with a Peltier cooler is, what happens if the thermistor ...