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Implantable capacitive absolute pressure and temperature monitor system

  • US 5,535,752 A
  • Filed: 02/27/1995
  • Issued: 07/16/1996
  • Est. Priority Date: 02/27/1995
  • Status: Expired due to Term
First Claim
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1. A capacitive pressure and temperature sensing system for providing signals representative of magnitude of body fluid absolute pressure at a selected site and ambient operating conditions, including body temperature at the site comprising:

  • an elongated implantable lead body having proximal and distal end sections and having first and second electrical conductors extending from the proximal end section to the distal end section, said distal end section adapted to be implanted in a selected body site;

    a sensor module formed in the distal end section of the lead body having pickoff and reference capacitor means formed therein and sharing a common charge plate;

    sensor circuit means within said sensor module electrically connected to said pickoff and reference capacitor means and said first and second electrical conductors including temperature conversion means for generating a charge current and a discharge current varying with ambient temperature at the selected site, charging and discharging means for alternately charging and discharging said pickoff and reference capacitor means with said charge and discharge currents between selected voltage levels, and pulse generating means for generating pickoff and reference timing pulses separating pressure related and temperature related charge time intervals of said pickoff and reference capacitor means varying as a function of said charge current and capacitance changes of said pickoff capacitor means;

    means for providing a bias voltage and current to said first and second electrical conductors for powering said sensor circuit means; and

    demodulating means coupled to said first and second conductor means and responsive to said pickoff and reference timing pulses for discriminating and converting said pressure and temperature related time intervals into pressure and temperature signals.

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