초록 ▼

A liquid level detecting system for detecting a conducting liquid level in a non conductive container which utilizes a grounding rod mounted in a lower portion of the container and a conductive sensing rod mounted at a position above the grounding rod. An oscillator is provided having a frequency in

A liquid level detecting system for detecting a conducting liquid level in a non conductive container which utilizes a grounding rod mounted in a lower portion of the container and a conductive sensing rod mounted at a position above the grounding rod. An oscillator is provided having a frequency in the range of about 600 hertz to about 100 kilohertz. The output of the oscillator is applied to the sensing rod through a high impedance circuit and a high pass filter. In another embodiment, the high pass filter may have the higher end frequencies attenuated to produce a band pass filter which selectively passes the frequency of the oscillator. The voltage drop across the circuit which includes the conductive sensing rod to ground is detected by a voltage peak detector and a threshold detector to produce an output which detects the drops in voltage when the conductive fluid level in the tank rises so that both the sensing rod and the grounding rod are covered, completing the circuit. In another embodiment, multiple sensing rods may be positioned at various heights in the tank to detect various fluid levels. The use of the high pass or band pass filters in series with the sensing rod and ground will eliminate any DC current in the rods thereby reducing electrolysis. The filters also eliminate or significantly reduce interference or artifacts due to DC and 60 hertz.

대표청구항 ▼

[ We claim:] [1.] A liquid level detecting system for detecting a conductive liquid level in a container, comprising:a conductive AC grounding rod mounted in a lower portion of said container;a conductive sensing rod mounted in said container at a position above said conductive grounding rod;an osci

[ We claim:] [1.] A liquid level detecting system for detecting a conductive liquid level in a container, comprising:a conductive AC grounding rod mounted in a lower portion of said container;a conductive sensing rod mounted in said container at a position above said conductive grounding rod;an oscillator for producing an output having a frequency in the range of about 600 hertz to about 100 kilohertz;a circuit for supplying the output of said oscillator at a high impedance output to said conductive sensing rod;a circuit being completed through said, conductive sensing rod and said conductive AC grounding rod when a conductive liquid in the container immerses both said conductive sensing rod and said conductive grounding rod, said circuit including an electrical filter circuit which blocks DC and passes AC above 600 hertz; andcircuit means for sensing a change in the voltage developed across said circuit when the conductive liquid in said container first reaches a level to immerse both said conductive grounding rod and said conductive sensing rod.