Table of Contents
IntrodcutionIntroduction
The physical quantity
Working principle
Pressure sensors types
Sensor characteristics
Applications
References
The physical quantity
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Pressure from resistance variation
The In Figure 2A the applied pressure causes deformation of the sensing element (for example diaphragm) causes displacement of the wiper of a potentiometer (Figure 2A) or a change of resistance in a metal strain gauge (Figure 2B). The output voltage is then proportional to the measured pressure, which is connected to a strain gauge that exhibits a change in resistance when mechanically strained. The value for pressure is then obtained by reading the variation of the output voltage which is proportional to the change in resistance of the strain gauge.
Similary, in Figure 2B a wiper (moveable electrical contact) is mechanically linked to the diaphragm and the applied pressure controls the wiper's position. This affects on the length of the wire (representing the resistance) between the wiper and the end of a potentiometer (variable resistance). The measurement for pressure is then obtained from the output voltage determined by the resistance value.
Pressure from capacitance variation
Here the sensing element, such as diaphragm, is connected to one of the electrodes of a capacitor. A change in the effective area of the plates (Figure 3A) , the distance between the plates (Figure 3B), or the relative permittivity of the dielectric (Figure 3C) creates a change in capacitance which reflects on the output voltage, from where the pressure can be derived.
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