Proximity sensor for level sensing

#1. The Technical Field

#The present invention is directed generally to level sensing. More particularly, the present invention is directed to proximity sensors having electrodes adapted for sensing level of fluids and other substances.

#2. The Prior Art

#FIG. 1 is a representation of an electrode design according to the present invention;

#FIG. 2 is a representation of an alternative electrode design according to the present invention; and

#FIG. 3 is a representation of a plurality of sensors having electrode designs according to the present invention for measuring the level of a substance in a tank.

#FIG. 1 illustrates a field effect sensor 10 located on the side wall 22 of a tank 20 containing a fluid, such as the gas tank of an automobile. In other embodiments, tank 20 could contain multiple fluids or a powder. Preferably, sensor 10 is located on the outside of tank 20, but also could be located on the inside of tank 20. Alternatively, sensor 10 could be embedded within the side wall 22 of tank 20.

#Sensor 10 includes first and second, substantially parallel, electrodes 12,14 coupled to a control circuit 16. Preferably, control circuit 16 is embodied as the control circuit provided with the TS100 sensor available from TouchSensor Technologies, LLC of Wheaton, Ill. Many of the design and operating principles of the TS100 sensor are described in U.S. Pat. Nos. 6,230,282 and 6,713,897 and related U.S. patent application Ser. Nos. 10/272,377 10/725,908, the disclosures of which are incorporated herein by reference.

#Electrodes 12,14 differ from conventional sensor electrodes in that they are generally elongated and parallel. Preferably, electrodes 12,14 are disposed on tank 20 such that their longitudinal axes are substantially parallel with the surface of the fluid contained within tank 20. Generally, the greater the ratio of electrode length to width, the more quickly sensor 10 responds to stimuli proximate to an electrode, as discussed further below. Also, closely spaced pairs of electrodes provide greater resolution. That is, a sensor 10 using a closely spaced pair of electrodes generally is more sensitive to small changes in level a sensor 10 using a widely spaced pair of electrodes. However, a sensor using a closely spaced pair of electrodes may be more prone to providing erratic indication resulting from, for example, sloshing of fluid within tank 20.