Capacitance Level Measurement
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چکیده
A capacitor is formed when a level-sensing electrode is installed in a vessel. The metal rod of the electrode acts as one plate of the capacitor and the tank wall (or reference electrode in a non-metallic vessel) acts as the other plate. As the level of the material being measured rises, the air or gas normally surrounding the electrode is displaced by the material’s different dielectric constant. The value of the capacitor changes because the dielectric between the two plates has changed. RF capacitance instruments detect this change and convert it into a relay actuation or proportional output signal. The following equation illustrates the capacitance relationship:
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