Thermistor compensation for ambient temperature change - has directly and indirectly heated thermistors in differential amplifier circuit

摘要

The compensation circuit for indirectly heated thermistors has a differential amplifier (DV) with feedback resistor and potential divider resistors (R1, R2) connected to its inverting input. An indirectly heated thermistor (RH2) and the thermistor which is to be controlled (RH1) have their heaters connected in series and are connected between the negative pole of the supply and the amplifier output (A). One side of the auxiliary thermistor (RH2) is connected to the non-inverting amplifier input via a directly heated thermistor (R5) and fixed resistor (R4). - A rise in ambient temperature causes the resistance of the directly heated thermistor and the auxiliary thermistor to fall which also reduces the input voltage to the amplifier. The control thermistor is therefore compensated by the amplifier output circuit change.