Implantable calibration means and calibration method for an implantable

Abstract

An implantable body transducer having a self-contained calibration means. An exemplary embodiment comprises an implantable body pressure measuring transducer utilizing an L-C oscillator having a resonant circuit comprising a fixed L and a variable C, the variable C having a fixed capacitive electrode and a movable capacitive electrode in the form of a stiff pressure responsive diaphragm, the output frequency of the oscillator being a function of the pressure sensed by the diaphragm. The transducer incorporates a self-contained calibration means which contains predetermined calibration data with respect to the variable C. The predetermined calibration data is stored in a plurality of PROM storage elements which are sequentially addressed in accordance with the output of a counter, the PROM storage elements providing a serial bit stream which can be used to pulse-code modulate the L-C resonant circuit output. Specific calibration parameters for the variable C are determined during manufacture of the pressure measuring transducer. These parameters are programmed into the digital storage elements of the PROM, burned in, and then utilized to modulate the resonant circuit output subsequent to implantation in a body. In addition, a means is disclosed whereby other parameter measuring transducer outputs, such as a temperature, can be utilized through appropriate circuitry to modulate the output of the implantable body transducer.