A sensor signal processor

This paper describes a universal sensor interface named the sensor signal processor (SSP). The SSP consists of digital and analog blocks. The digital block generates a waveform which simulates the sensor characteristic in the time domain. An analog block processes a sensor output in the form consistent with the output of the digital block. Comparing both the outputs the SSP provides a linear digital equivalent of the measurand. For generating the waveform, the direct digital synthesis (DDS) and oversampling delta-sigma demodulation techniques are used. Eliminating precision devices, these techniques allow the high yield, monolithic implementation. The scale adjustment and cancellation of the offset and cross-sensitivity are also possible by adjusting the reference voltage involved in the DDS. Thus, the SSP satisfies almost all requirements for a universal interface. An application to a capacitive pressure sensor is also given to demonstrate its validity