Patent ID: 8181517
Filing Date: 2012-05-22
Classification: G01F

Abstract:
1. A sensor for measuring the level of contaminative substance in a tank, comprising: a float mechanism located inside the tank to move with changes in the level of the contaminative substance; a sender card having a variable resistor, at least a portion of the sender card in fluid communication with the contaminative substance; a wiper coupled to the float mechanism and making electrical contact with the variable resistor at a position determined by the position of the float mechanism; and a variable voltage supply coupled to one of the wiper and the sender card so that contact of the wiper with the variable resistor closes a circuit permitting current to flow from the variable voltage supply through the variable resistor; wherein the variable voltage supply is configured to supply a steady-state operating voltage within a first range and periodic voltage at a surge level above the first range; the surge level being selected to provide enough additional power to heat the variable resistor to an elevated temperature sufficient to remove at least a portion of the contamination accumulating on the sender card.