A DSP-based active sensor interface performing on-line fault detection and identification

Process-measuring instruments generating output signals in the form of a frequency are discussed. By applying a specific signal-analysis technique, which can be implemented by a mixture of hardware and software enhancements on a digital signal processor (DSP), it becomes possible to determine abnormal instrument operation and detect a faulty instrument component within minutes after its failure. The technique used comprises the transformation of the received signal to a train of unit pulses and its spectral analysis by the zero-crossing method. Although this technique presents a limited fault-discrimination ability, it can trace down quickly and economically the causes of major faults, as demonstrated by an application example