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Telemetering intracranial pressure transducer

  • US 4,471,786 A
  • Filed: 04/20/1982
  • Issued: 09/18/1984
  • Est. Priority Date: 04/27/1981
  • Status: Expired due to Fees
First Claim
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1. A telemetering intracranial pressure transducer comprising:

  • an airtight housing adapted to engage the skull of a body to be tested;

    a pressure-electric transducer having a pressure-sensing portion, disposed in said housing for detecting an intracranial pressure below a dura under the skill wherein said pressure-electric transducer comprises two strain-sensitive elements in a full bridge circuit;

    a pressure-receiving layer disposed in said housing and located at a frontal end of said housing in contact with said pressure-sensing portion of said pressure-electric transducer, said pressure-receiving layer being in pressed engagement with said dura; and

    a transmitting circuit disposed in said housing for transmitting an output signal from said pressure-electric transducer through a transmitting antenna wherein said transmitting circuit comprises a telemetering transmission circuit connected to said pressure-electric transducer for transmitting an output therefrom and microbatteries for supplying electric power to said pressure-electric transducer and said telemetering transmission circuit with said transmission circuit further comprising a switching means connected to said microbatteries for switching on and off said microbatteries and wherein said telemetering transmission circuit includes a subcarrier oscillator circuit connected to said pressure-electric transducer for modulating an output signal therefrom into a predetermined signal and wherein said telemetering transmission circuit further includes a main carrier oscillator circuit connected to said subcarrier oscillator circuit for transmitting an output signal therefrom with said subcarrier oscillator circuit comprising an astable multivibrator for frequency-modulating a carrier frequency including a full bridge circuit for delivering an electrical signal corresponding to a pressure variation, a differential amplifier connected to said full bridge circuit for amplifying said electrical signal therefrom, a comparator having a first input terminal, a second input terminal connected to said differential amplifier and an output terminal connected to said full bridge circuit, an integrating circuit connected to said first input of said comparator, and a filter circuit connected to said output terminal of said comparator for cutting off a d.c. component in an signal fed thereto and supplying a subcarrier signal to said main carrier oscillator circuit.

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