 Piezoresistive sensors from Kistler are used for measuring gas and liquid pressures and for truly static pressure measurement. Precise, reproducible results are achieved under even the most adverse conditions. The term piezoresistive implies that an electrical resistance is changed by pressure. With piezoresistive measurement, an elastic diaphragm of single-crystal silicon is deflected under pressure. A Wheatstone bridge made of semiconducting resistor elements is diffused into the diaphragm. As this bridge is unbalanced in proportion to the pressure applied, it produces a similarly proportional voltage, which is then amplified and analyzed. Integrated circuit technology allows extremely small resistor networks and active elements to be integrated on the silicon chip, which can be designed to act as a pressure diaphragm as well. The main advantages of this technology over conventional metal strain gages are high sensitivity compactness and high natural frequency. Piezoresistive measuring cells made of silicon have excellent static measuring characteristics. Silicon is a single crystal and remains elastic up to its breaking point. It does not undergo any plastic deformation. For this reason, silicon cells are very stable and their properties do not change even over a long period of time. Their dynamic characteristics are also excellent. As a result of their small dimensions, the natural frequency of the silicon cells is very high. Depending on the pressure range (diaphragm thickness), it can be between 15 and 200 kHz. Back to Technology
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