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Monitoring and indicating circuit for reverse osmosis filter

  • US 4,937,557 A
  • Filed: 01/02/1990
  • Issued: 06/26/1990
  • Est. Priority Date: 01/02/1990
  • Status: Expired due to Fees
First Claim
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1. A monitoring and indicating circuit for a reverse osmosis water filtering system of the type having a raw water inlet pipe and a filtered water outlet pipe and a reverse osmosis filter cartridge disposed therebetween, comprising:

  • (a) first and second conductivity cells, the first disposed in said water inlet pipe and the second in said water outlet pipe;

    (b) variable gain amplifier means including an operational amplifier having an input terminal and an output terminal;

    (c) signal generating means for producing an AC signal of a predetermined frequency and amplitude;

    (d) means coupling said second conductivity cell in series between said signal generating means and said input terminal of said operational amplifier;

    (e) means coupling said first conductivity cell between said output terminal and said input terminal of said operational amplifier;

    (f) peak detecting means with an input terminal connected to said output terminal of said operational amplifier and an output terminal;

    (g) comparator means for comparing a signal proportional to the peak-voltage signal at said output terminal of said peak detecting means with a predetermined reference voltage; and

    (h) indicator means coupled to said comparator means for indicating whether said signal proportional to the peak voltage signal is greater than or less than said predetermined reference voltage.

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