Thermistor principle of temperature measurement
The resistance of metal thermal resistance value and temperature can be expressed by the approximate relation of the following, namely Rt=Rt0[1+ alpha (t-t0)] in the formula, Rt temperature T value; Rt0 temperature t0 (usually t0=0 C) when the corresponding resistance value; a temperature coefficient. The relationship between the resistance and temperature of the semiconductor thermistor is Rt=AeB/t. The value of the resistance at Rt is t, and the A and B depend on the constants of the structures of the semiconductor material. In comparison, the temperature coefficient thermistor resistance is greater, under normal temperature high (usually in Europe, but thousands more) bad interchangeability, serious nonlinear, only the temperature range of -50~300 degrees Celsius, widely used in temperature detection and control of home appliances and automobiles. Metal thermal resistance is generally applicable to temperature measurement in the range of -200~500 centigrade. It is characterized by accurate measurement, good stability, reliable performance and wide range of application in process control.
Any resistance will increase with the temperature, the resistance increases, the thermistor changes more obvious, but the temperature changes are not linear, it is the curve. A section of an approximate line. If higher precision is required, software compensation can be used. The actual circuit is usually measured thermal resistance voltage, resistance changes, voltage will change, and then converted to digital signals through the AD, using single-chip microcomputer to process these data.
Thermistor principle of temperature measurement and thermocouple temperature measurement principle is different, the thermal resistance is based on the thermal effect of resistance to temperature measurement, that is, the resistance of resistance with the change of temperature characteristics. Therefore, the temperature can be measured as long as the resistance change of the sensing thermal resistance is measured. At present, there are two kinds of metal thermal resistor and semiconductor thermistor.
