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Enraf level gauge is based on the ser powered null balance technique. A displacer serves as continuous level sensing element. A two phase ser motor controlled by a capacitive balance system winds unwinds the the measuring wire until the tension in the weight springs is in balance with the weight of the displaced part immersed in the liquid. The sensing system in balance measures the two capacitance formed by the moving central sensing rod provided by the two capacitor plates and the si plates.
The physical principle is to measure the variation in a torque due to the variation of the force caused by a liquid levitated mass. This mechanical variation is designed to generate electromagnetic variations that can be measured and expressed in function of the displacement.
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