Liquid absence detector
First Claim
1. A device for detecting the absence of liquid in a liquid chamber, said device comprisingtransmitter means for transmitting a signal through the chamber, andreceiver means for receiving the transmitted signal after its transmission through the chamber, said receiver means comprisinga receiving transducer for receiving an AC signal,an amplifier,a capacitor AC coupling said transducer to said amplifier,DC control circuit means for receiving an AC signal and for generating an output voltage the amplitude of which is proportional to the peak-to-peak amplitude of the received AC signal,means for coupling the amplified AC signal from said amplifier to said DC control circuit means,a comparator,means for providing a reference voltage to one input of said comparator,means for coupling said DC control circuit output voltage to the other input of said comparator, the amplitude of said DC control circuit output voltage being proportional of the peak to peak amplitude of said amplified AC signal, andsaid comparator output providing a liquid absence detection signal in response to the difference between said reference voltage and said DC control circuit output voltage.
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Accused Products
Abstract
A system is provided for detecting the absence of liquid in a liquid chamber. A signal is transmitted through a liquid chamber and a signal is provided in response to the amplitude of the received signal. A receiving transducer receives an AC signal which is amplified and fed to a DC control circuit. A reference voltage is provided to one input of a comparator and the output of the DC control circuit is fed to the other input of the comparator. The comparator output provides the liquid absence signal if the difference between the reference voltage and the DC control circuit output voltage is less than a predetermined value.
35 Citations
13 Claims
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1. A device for detecting the absence of liquid in a liquid chamber, said device comprising
transmitter means for transmitting a signal through the chamber, and receiver means for receiving the transmitted signal after its transmission through the chamber, said receiver means comprising a receiving transducer for receiving an AC signal, an amplifier, a capacitor AC coupling said transducer to said amplifier, DC control circuit means for receiving an AC signal and for generating an output voltage the amplitude of which is proportional to the peak-to-peak amplitude of the received AC signal, means for coupling the amplified AC signal from said amplifier to said DC control circuit means, a comparator, means for providing a reference voltage to one input of said comparator, means for coupling said DC control circuit output voltage to the other input of said comparator, the amplitude of said DC control circuit output voltage being proportional of the peak to peak amplitude of said amplified AC signal, and said comparator output providing a liquid absence detection signal in response to the difference between said reference voltage and said DC control circuit output voltage.
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7. A device for detecting the absence of liquid in a liquid chamber, said device comprising
transmitter means for transmitting a signal through the chamber said transmitter means comprising an oscillator, a plurality of NOR gates connected to operate as an amplifier stage, a pair of push-pull transistors, means coupling the output of said amplifier stage to the input of said push-pull transistors, and a transmitting crystal coupled to the output of said transistors, and receiver means for receiving the transmitted signal after its transmission through the chamber.
Specification