Patent ID: 8057401

Claim:
An implantable biometric sensor comprising: a subcutaneous case; an access portal in the case to an internal fluid; a sensor within the case generating a signal related to a property of the internal fluid; a conversion circuit within the case transforming the signal into a transmitted near infrared optical form; and an inductive power coupling providing power to the sensor and the conversion circuit; and, the sensor is an oscillated crystal comparator further comprising an isolated reference crystal exposed to a reference pressure and connected to a reference oscillator; wherein said reference crystal produces a first frequency signal upon excitement thereof; a transducer crystal exposed to said internal fluid and connected to a transducer oscillator; wherein said transducer crystal produces a second frequency signal upon excitement thereof; a heterodyne amplifier connected to the transducer oscillator and the reference oscillator to generate a frequency difference between the first frequency signal and the second frequency signal to compute said property of said internal fluid.