Bending pressure sensor

Fig. 5.60 Pressure sensor with ceramic bending beam.

Figure 1 illustrates the operational principle of hydrogel-based sensors. Pressure sensor chips with a flexible thin silicon bending plate and with an integrated piezoresistive Wheatstone bridge inside this plate have been employed as... 

The fiber optic sensors utilize an extrinsic Fabry-Perot interferometer to spectrally modulate light in proportion to pressure, temperature, or refractive index variations. Because they are based on spectral modulation instead of amplitude modulation, they are not affected by such common problems as fiber bending, connector losses, and aging. 

Figure 17. Response of the catheter-protected porphyrinic sensor to changing fluid pressure (a), to mechanically bending the active tip of the sensor at a frequency of 3Hz (b), and to the ECG signal (c). The vertical bars represent the equivalent current that would be generated by the porphyrinic sensor in the 100 nM NO ((a), lower tracing) or 50 nM NO (b).

There are two types of sensors to be distinguished axial and bending sensors. In the case of an axial sensor the force works in the polarization direction, while for the bending sensor the force works perpendicularly to it. Concerning the latter, emerging tensile or pressure forces depend on the distance of the active material from the neutral fiber [91]. 

The additional elements possibly present along a given pipeline can be widely variable bends (elbows) and other directional variations, connections like tees and others, cross-sectional area variations (restrictions, enlargements), joints (welds, flanges, others), orifices, nozzles, sensors for instrumentation, all different kinds of valves, and many others. All these elements introduce a pressure loss to the flowing fluid, which is not easy to predict because of both the extreme variability of those elements, and the difficulties in the mathematical representation of the flow characteristics through them. 

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