Digital Processing of Differential Transducer Signals

A method is described for digitally processing two frequencies produced by placing a pair of differential transducers in parameter controlled oscillators. For frequencies that are either directly or inversely related to the measured variable, the output count is proportional to the measured variable. The method does not rely on the accuracy of an external clock, but instead uses the two frequencies themselves to determine the sampling period. As a result, the accuracy is independent of clock frequency and is unaffected by equal compression or stretching of the two signals during recording or transmission. In addition, errors due to the discrete nature of the counting process are less than similar errors in a more conventional method.