Patent ID: 7573263

Claim:
A method of using a device for determining a value of a magnetic field, the method comprising: said device rectifying an alternating voltage output from at least one coil in an alternating magnetic field; said device controlling a voltage controlled oscillator using the rectified voltage; said device outputting a signal from the voltage controlled oscillator, wherein the signal has a frequency that depends on an amplitude of the magnetic field at the at least one coil; said device chopping current in a modulation resistance connected between the rectified voltage and a switching device that receives the signal from the voltage controlled oscillator, wherein current through a modulation resistance is chopped at the frequency of the signal from the voltage controlled oscillator which results in modulating current in the at least one coil; and said device determining a value of the magnetic field by demodulating an output voltage of an antenna coupled to the at least one coil, wherein the output voltage alternates at a frequency of the magnetic field and is modulated in amplitude at the frequency of the signal from the voltage controlled oscillator; wherein said at least one coil, the voltage controlled oscillator, the modulation resistance and the antenna are carried by said device.