Noise in piezoresistive pressure sensors

In this paper we present the results of noise analysis in piezoresistive ceramic pressure sensors (CPSs) prepared by low temperature co-fired ceramics (LTCC) technology. For this study a piezoresistive CPSs in a full Wheatstone-bridge configuration were prepared. Low frequency noise measurements can be used for the quality evaluation of CPSs. The critical and non-critical defects could be determined from the noise measurements. Increased value of spectral density of sensor output voltage fluctuation gives the information about the cracks and structural defects in sensing resistor´s structure as well as about the crack in sensor´s diaphragm. We propose parallel/series configuration of resistors for measurement of particular sensing resistor influence on the total sensor noise. In this case the noise spectral density of single resistor in parallel to three resistors in series is 8 to 10times higher comparing to the noise spectral density of each of these three resistors in series. Then the sensing resistors with structural defects could be identified from the noise measurements.