In this paper we propose a feedback measurement system, with thermoresistive sensor, based on sigma-delta modulation. The system uses a one-bit sigma-delta modulator for which a considerable part of the conversion functions is performed by a thermoresistive sensor. The sensor is modelled using the power balance principle and the constant temperature measurement method is employed. This transducer architecture is able to realize digital measurement of physical quantities that interacts with the sensor: temperature, thermal radiation and fluid velocity. This paper presents simulations and validates the structure of the sigma-delta converter as an anemometer. The advantage to directly convert physical quantities to digital, with the sensor as part of the A to D converter, makes possible the implementation of this measurement system in an integrated circuit. Another advantage of the IC implementation of this structure is the possibility to reduce noise interference due to discrete component connections in a printed circuit board.