An inherently linear transducer using thermistor practical approach

In this article we describe a feedback circuit, with thermoresistive sensor, based on thermal sigma-delta modulator. This circuit uses a one-bit first order sigma-delta modulator in which considerable part of conversion functions is performed by the sensor. This transducer circuit is able to perform digital measurement of physical quantities that interacts with the sensor: temperature, thermal radiation and fluid velocity. In this paper, this circuit was used to measure environment temperature. In this circuit, digital output voltage is linearly dependent on the environment temperature. We show the equations that support circuit behaviour, simulation results and experimental results. In addition, we present the thermal radiation architecture version in which digital output is intrinsically linear to the thermal radiation measure.