Computer Controlled Cryogenic Temperature Controller

In laboratories which do materials characterization it is necessary to have a temperature controller which can be computer controlled, is accurate to within .1-.2K, can control temperature from 15-350K with a drift of no more than .1, and is relatively unaffected by the presence of a magnetic field on the sample container. The subject controller uses two thermometers to meet these requirements. One is a commercially available calibrated silicon diode manufactured expressly for this type of application. The second thermometer is used for control. Once the sample has reached the setpoint according to the calibrated thermometer the control thermometers value is sampled and used as the new setpoint. Since the control thermometer should be insensitive to a mag field the sample will remain at the desired temperature when the magnetic field is applied. eg