This circuit is from an English publication of 1982. The bipolar transistor can be a BC548 and the MOSFET any type according to the relay. The circuit works in a pulsating regime to present an extremely low consumption. The sampling pulse generator can be a CMOS oscillator. The sensor is an NTC and the adjustment trimpot must have the same order of value as this component at room temperature. The relay is 12 V, and the signal conditioner must guarantee an output without bounces for processing.
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