Abstract: A transducer for measuring temperature by means of the temperature-induced resistance change of a coil of wire includes, connected to the coil, a deposited film whose resistance-versus-temperature characteristic is substantially the same as that of the wire. The complete transducer assembly is calibrated at a fixed temperature by physically removing portions of the deposited film until a desired resistance is attained. The bulk of the resistance is contributed by the wire, while the film contributes only a small percentage of the total. The transducer thus maintains the desired precision, repeatability and stability of a wirewound transducer while at the same time being capable of calibration by trimming techniques commonly used for adjusting film resistors.

Abstract: An apparatus for measuring the differential between a plurality of physical quantities, such as temperature, includes transducers 10 and 12 each positioned to sense the physical quantity. The transducers are preferably of the resistive or nonreactive variety. A single, controlled current power source 15 is connected sequentially to the transducers through a switching circuit 20. Each transducer is connected to the switching circuit and to an amplifier 40 through four-conductor cables 35, 45. The amplifier is therefore connected continuously to the transducers to sense both the voltage developed thereacross when the transducer is connected to the source of current through the switching circuit and also to sense continuously any other voltages, such as those that might be produced by thermocouple effects.