Donald Y Daily2601 Andrew Rd, Marple Township, PA 19008

4819483, Apr 11, 1989

Jul 12, 1988

7/219864

Raymond H. Emplit - Glen Mills PA
Donald Y. Daily - Havertown PA

Custom Controls Co., Inc. - Broomall PA

G01F 2300

73304C

A level indicator control system including a microprocessor that controls the height and, therefore, the amount of the substance, such as fluid or granular solid, to be contained in a closed or open tank or vessel. The system provides calibrated digital or analog output that shows the extent to which the tank is filled with substance at substantially any level. A scale, in percent, each value representing the percentage of fullness of the tank, is produced after low and high limits, representing any low and high substance levels respectively, are provided to the microprocessor. The scale values are a function of the changes in capacitance between the stationary probe and the tank wall as the level of substance approaches or submerges the probe. The system finds its probe capacitance and sets its own high and low control set point limits automatically. Thereafter, the system uses the instantaneous probe capacitance and the capacitance values representing the high and low substance levels to provide the calibrated digital or analog output.