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Apparatus for measuring fluid level

  • US 3,110,890 A
  • Filed: 03/03/1958
  • Issued: 11/12/1963
  • Est. Priority Date: 03/03/1958
  • Status: Expired due to Term
First Claim
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1. IN APPARATUS FOR DETERMINING THE CONDITIONS OF PRESENCE AND ABSENCE OF A FLUID AT A LOCATION THE COMBINATION OF AN OSCILLATORY CIRCUIT COMPRISING AN AMPLIFIER HAVING A PLURALITY OF STAGES OF AMPLIFICATION AND A FEEDBACK NETWORK INCLUDING AN ELECTROMECHANICAL TRANSDUCER HAVING A PAIR OF ELECTRODES, SAID TRANSDUCER BEING ADAPTED TO VIBRATE MECHANICALLY UPON THE APPLICATION OF AN ALTERNATING POTENTIAL ACROSS SAID ELECTRODES, SAID FEEDBACK NETWORK INCLUDING A FOUR TERMINAL BRIDGE CIRCUIT, THE OUTPUT OF SAID AMPLIFIER BEING CONNECTED ACROSS A FIRST OPPOSING PAIR OF SAID TERMINALS AND THE INPUT OF SAID AMPLIFIER BEING CONNECTED ACROSS A SECOND OPPOSING PAIR THEREOF WHEREBY THE UNBALANCE SIGNAL IN SAID BRIDGE IS APPLIED TO SAID INPUT, SAID TRANSDUCER BEING CONNECTED INTO ONE ARM OF SAID BRIDGE, SAID FEEDBACK NETWORK BEING SO CONNECTED THAT POSITIVE FEEDBACK IS APPLIED TO SAID INPUT AT A RESONANT FREQUENCY OF SAID TRANSDUCER, SAID TRANSDUCER BEING MECHANICALLY COUPLED TO SAID LOCATION, WHEREBY THE CHARACTERISTICS OF OSCILLATION OF SAID CIRCUIT VARY IN ACCORDANCE WITH THE PRESENCE OR ABSENCE OF SAID FLUID AT SAID LOCATION AND MEANS FOR DETECTING CHANGES IN THE OSCILLATORY CHARACTERISTICS OF SAID CIRCUIT.

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