Digital electronic thermostat with correction for triac self heating

An electronic thermostat having a correction for self heating comprising:

• a semiconductor power switching device controlled for selective connection of electric power to a temperature control unit;
• a first thermistor disposed at a location remote from said semiconductor power switching device, having a resistance which varies with ambient temperature;
• a second thermistor disposed at a location intermediate between said semiconductor power switching device and said first thermistor, having a resistance which varies with ambient temperature;
• a microprocessor unit connected to said semiconductor power switching device, said first thermistor and said second thermistor, said microprocessor device including
• a first temperature measurment means connected to said first thermistor for determining the first temperature indicated by the resistance of said first thermistor,
• a second temperature measurment means connected to said second thermistor for determining the second temperature indicated by the resistance of said second thermistor,
• a temperature correction means connected to said first and second temperature measurement means for generating a corrected temperature signal from said first temperature and said second temperature,
• a desired temperature means for generating a desired temperature signal indicative of a desired temperature,
• a control unit connected to said semiconductor power switching device, said temperature correction means and said desired temperature means for controlling the state of said semiconductor power switching device based upon the relationship of the corrected temperature signal and said desired temperature signal.