LIQUID_LEVEL_CHECKER

Published:2009/7/6 9:29:00 Author:May | From:SeekIC

Although many circuits use the varying-capacitance method for checking liquid levels, this simple resistive circuit is much easier to construct. Even a tank of a liquid, such as water, has sufficient conduc-tive salts in solution for this method to work. The probe uses a metal rod that supports 10 insulated wires, which have stripped ends pointing down. As the level of liquid rises, resistors R1 through R10 are succes-sively brought into circuit, each drawing an extra 10 μA through the meter. Shunt resistors R11 and R13 calibrate the meter for a full-scale reading when the tank is full. Resistor R12 limits the current through the meter. If tank isn't rectangular-ie, if the volume of the liquid it contains isn't directly proportional to the liquid's depth-space the resistors accordingly or use a nonlinear progression of resistor values and retain constant resistor spacing.



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