Correction for Self-Heating When Using Thermometers as Heaters in Precision Control Applications

In precision control applications, thermometers have temperature-dependent electrical resistance with germanium or other semiconductor material thermistors, diodes, metal film and wire, or carbon film resistors. Because resistance readout requires excitation current flowing through the sensor, there is always ohmic heating that leads to a temperature difference between the sensing element and the monitored object. In this work, a thermistor can be operated as a thermometer and a heater, simultaneously, by continuously measuring the excitation current and the corresponding voltage. This work involves a method of temperature readout where the temperature offset due to self-heating is subtracted exactly.