Patent ID: 8725245

Claim:
A noninvasive apparatus for measuring a condition of a specimen comprising: A noninvasive oscillator providing a reference signal having a phase and a fixed frequency; A noninvasive tunable reactive circuit receiving the reference signal from the oscillator, said tunable reactive circuit containing an induction coil adapted to be positioned on a surface of the specimen and connected in series with a varactor type diode to form an RLC circuit and generating an oscillating signal corresponding to the condition of the specimen, said oscillating signal having a frequency and having a phase, said tunable reactive circuit providing an output signal having a parameter indicative of the condition of the specimen, wherein the parameter comprises an impedance of an element of said tunable reactive circuit, the impedance linearly relating to a conductivity of the specimen; and A noninvasive resonant control circuit comparing the reference signal to the oscillating signal and providing to the tunable reactive circuit a resonance control signal representative of the comparison, said resonance control signal tuning the tunable reactive circuit to resonance at the fixed frequency of the oscillator while the impedance of the element of said tunable reactive circuit is measured.