Evaluating circuits convert the signal supplied by a measuring instrument and proportional to a measured value into an electric quantity suitable for further processing. In the evaluating circuit according to the invention, it should be possible to connect a measuring instrument to the evaluating circuit in a potential-isolated manner. Due to the fact that the measuring instrument can be connected as load to the secondary winding (52) of a transformer (5), there is direct-current isolation between the sensor element and the corresponding evaluating circuit. The changes in the measured quantities detected over time by the measuring instrument produce a change in the load and thus a proportional change in the damping on the transformer (5). This change in damping is converted into an electric signal suitable for further processing. The evaluating circuit can be used wherever a change with time of a measured quantity leads to a proportional resistance change. <IMAGE>
