Abstract: A two wire and a three wire resistive fluid level sensor for measuring fluid levels within a container are disclosed. The sensor includes a plurality of resistors connected in series. The sensor produces an output signal by providing a short circuit to the circuit nodes between the resistors so that a stair-step output signal is created as the float moves in conjunction with the liquid level in a container. The value of the resistances can be varied in order to accommodate various cross-sectional tank contours and thus produce a usable, readily and easily configurable sensor. The structure of the sensors enables measurement of depth variances far in excess of prior art sensors.

Abstract: A liquid level sensor for sensing liquid levels within a container is disclosed. The sensor includes a conductive plastic resistor and conductive plastic conductors deposited onto a thin polymer insulator. The conductive plastic resistor is a potentiometric resistive track which is electrically contacted at points along the length of the resistor by a contact assembly attached to a float. The polymer insulator is attached to a conductive support member or conductive strip disposed substantially vertically in the liquid. The float is disposed about the conductive strip. The contacts provide a short circuit between the resistive strip and conductive strip and thereby provide a resistive circuit connection analogous to the wiper of a potentiometer.

Abstract: A method of trimming a resistance element is disclosed which comprises cutting transversely into one side of the element until the measured total resistance of the element increases by a fraction 1/N of a fixed percentage of a desired total resistance value. The fraction 1/N is approximately equal to the path length of the resistance element divided by the designed width of the transverse cut and the fixed percentage is equal to the percent deviation of the initial total resistance of the element from a nominal, desired resistance value. After the transverse cut is made, a longitudinal-type cut is made at a distance, equal to the length of the transverse cut, from the edge of the element having the transverse cut to isolate a portion of the element from the remainder of the element so that the isolated portion has the desired total resistance. This method is particularly suitable for use with computer controlled laser trimming systems used to mass produce resistance elements.

Abstract: A cermet resistor element utilizing a silver-gold alloy to improve the contact resistance variations and the method of making the element are disclosed. A gold resinate and a silver resinate are mixed with the noble metal resinates and glass frit to make a cermet material. The mixture is heated to drive off the organic resinate materials and to alloy the silver and gold. The resultant material is ground to a powder, reheated and reground. The powder is mixed with a volatile material to form a paste which can be applied to a substrate to form the resistance element. The element is heated to drive off the volatile material and fuse the glass into a solid mass. The silver and gold form a silver-gold alloy during the process and settle on the top surface of the element in globules and improve the contact resistance variations of the element.