RESISTANCE TYPE LIQUID LEVEL MEASURING APPARATUS

摘要

A resistance type liquid level measuring apparatus capable of an accurate measurement by confining the detection voltage error due to silver sulfide to within a practically allowable range, comprising a float (9) floating up and down depending on the liquid level, an insulation substrate (6) having a plurality of conductor electrodes (4) connected with resistors (5), and a resistance sensor having a movable contact interlocked with motion of the float (9) to touch the conductor electrode (4) on the insulation substrate (6). A material containing silver is employed in the conductor electrode (4) or the movable contact and a voltage dividing resistor (11) is connected with a power supply BA in series with the resistor (5) and voltage at the joint of the voltage dividing resistor (11) and the resistor (5) is outputted as a signal corresponding to the liquid level. Resistances of the voltage dividing resistor (11) and the resistor (5) are set such that a voltage drop VS caused by silver sulfide produced between the conductor electrode (4) and the movable contact does not exceed 15%, preferably 10%, of the difference between voltages VF and VE corresponding, respectively, to a full-tank liquid level and a lower region liquid level.