The capacitive liquid level meter measures the liquid level by measuring the change of capacitance. A metal rod is inserted into the liquid container, the metal rod is used as one pole of the capacitor, and the container wall is used as the other pole of the capacitor. The medium between the two electrodes is the liquid and the gas on it. Because of the dielectric constant of the liquid ε 1 and the dielectric constant on the liquid surface ε 2 different, for example: ε 1> ε When the liquid level rises, the total dielectric constant between the two electrodes of the capacitive liquid level meter increases, so the electric capacity increases. On the contrary, when the liquid level drops, ε The capacitance decreases with the decrease of the value. The electrode is usually wrapped with insulating layer, and the marine uses Teflon material. One of the basic requirements for measuring material level with capacitive liquid level meter is that the relative permittivity of the measured medium (the ratio of permittivity of the measured medium to that of air) should not change during the measurement process. The transmitter cooperated with the liquid level meter converts the capacitance change signal into the output of 4-20 mA current signal relative to the liquid level range after various compensation and calculation, which is used for the input of remote instrument or the signal acquisition of control equipment.

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