A common method for converting diaphragms displacement into a measurable signal is to sense the strain induced on the diaphragms surface as it is displaced. Strain gauges, device whose measurable resistance is proportional to their sensed strain (see chapter 11), can be bonded directly onto the diaphragms, Integrated within the diaphragms material or into a deforming element (such as a thin beam) attached to the diaphragms so as to deform with the diaphragms and to sense strain. Metal strain gauges can be used with liquids. Strain gauge resistance is reasonably linear over a wide range of strain and can be related to the sensed pressure (5), A diaphragm transducer using strain gauge detection is depicted in Figure 9.12.
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