Detection of defective sensor elements using correlation technique combined with sigma-delta-modulation

This paper presents a novel technique for detection of defective sensor elements. For this purpose the sensor element is electrically stimulated using a pseudo random binary sequence (PRBS). The sensor element signal is read out and the analog output is digitized using a sigma-delta-modulator. In case of a defect-free sensor system the binary pulse density output of the sigma-delta-modulator contains the PRBS. A matched filter is used as a corellator for detection of the PRBS in the binary output and its sampled output is compared to a threshold. This comparsion makes it possible to evaluate the functionality of the sensor system including the sensor element. Our solution for detection of detective sensor elements has been fully integrated using a 1.2µm CMOS process with only a moderate hardware overhead. Due to the small stimulation amplitudes using correlation technique no disturbance of the actual measurement happens.