Liquid level sensing system

#This invention relates to a liquid level sensing apparatus and system for use in a wide variety of equipment requiring the monitoring of liquid tanks such as spas, swimming pools, water tanks, etc.

#The concept of monitoring liquid such as water in a container to determine its depth or level in terms of some predetermined level and providing an electrical signal to indicate said change of level is not new. Many methods have been taught such as floats, thermocouples, sonic and temperature sensors, light reflections means, and other complicated mechanical apparatus and electrical circuits and components involving radioactive means, heat streams, amplifiers, etc. In the prior art a great amount of mechanical apparatus and electrical components and circuits have been used which require a large amount of space and expensive monitoring equipment which requires maintenance and qualified personnel to operate. Such level sensing arrangements and apparatus are also subject to signal error because of varying heat flow and temperature conditions of the liquid between measurement zones. Such signal errors are not capable of being reliably corrected by accumulated error data because of the often unpredictable nature of heat flow conditions within the liquid body being monitored.

#It is an object of my invention to provide a simple, reliable, liquid level sensing system that does not depend on heat or temperature as a sensing means.

#FIG. 1 is a front perspective view of the system showing the probe, wire harness and the indicating box and panel.

#FIG. 2 is a simplified partial side section view through a liquid level monitoring probe assembly in accordance with one embodiment of the invention, in association with a schematically illustrated signal processing system.

#FIG. 3 is a partial side section view through a liquid level monitoring probe taken at a*--a*.

#Referring now to the drawings, 13 is the body or casing of a probe while 15 is a monitoring panel containing indicator light 31 which is a tri-color light emitting diode that glows red when DC voltage is applied, glows green when reverse DC voltage is applied and glows yellow when AC is applied, such as is provided by THREE-FIVE SEMICONDUCTOR, INC. of Phoenix, Ariz., while 29 is an electrical box, 33 is an on/off switch, 17 is a suitable wiring harness with 11 being suitable mounts for probe 13, 19 being a typical conducting standoff for supporting contact elements 23,25, and 27 while 37 is a non-conductive standoff for supporting the opposite end of contact element 23, 25 and 27, while 21 is a conductive standoff, 10 being a step-down transformer such as 110/12 volts with AC supply 12 with 18 being a transistor such as RADIO SHACKS #2023, while 28 shows the red indicating zone, 30 shows the green indicating zone and 34 shows the yellow indicating zone with 20 being the liquid being sensed.

#It will be seen that the circuit is energized by line voltage 12 through transformer 10, switch 33, transistor 18 and LED 31 and when the liquid level 20 covers the contact 21 and the bottom end of wire element 23 and enters the bottom of zone 15, that the LED 31 will begin to dimly glow red and as the liquid level 20 rises, covering more of contact element 23, then the resistance of the circuit decreases making the LED 31 glow a brighter red. When the entire contact element 23 is completely covered the LED 31 glows a bright red and continues to glow a bright red as long as the liquid level is anywhere in zone 28. When the liquid level 20 reaches the bottom of contact element 25 and a circuit is formed the LED 31 will dimly glow green and as the liquid level 20 rises, covering more of contact element 25, the resistance of that circuit decreases making the LED 31 glow a brighter green and when the entire contact element 25 is completely covered, the LED 31 glows a bright green and continues to glow a bright green as long as the liquid level is in zone 30. Now when the liquid level 20 reaches the bottom of contact element 27, and a circuit is formed the LED 31 will dimly glow yellow and as the liquid level 20 rises, covering more of contact element 27, the resistance of that circuit decreases making the LED 31 glow a brighter yellow and when the entire contact element 27 is completely covered the LED 31 glows a bright yellow. The A.C. current as shown in FIG. 2 is supplied by transformer 10 while D.C. current and reverse D.C. current is supplied as shown by FIG. 2 through transistor 18.

#It will now be seen that by positioning another probe assembly above or below the first probe that a second LED may be energized, etc, so that any number of levels may be monitored.