The PMT thermoelectric cooler controller was developed for Oriel Corp. The purpose of this device is to control the temperature of a photomultiplier tube with integrated thermoelectric coolers. When operated at low temperatures, these PMT's exhibit very low dark current. The design included a linear, remotely adjustable temperature set point, and a type II servo system with 0 residual error from the set point. Additionally, the thermoelectric cooler's transfer function was linearized so that delta temperature divided by delta error voltage was constant at all operating points. This provided stable operation at all operating temperatures and eliminated the possibility of thermal runaway. Drive power was up to 4 amps at 16 volts.