Patent ID: 7405559

Claim:
A sensor electrical circuit comprising: a stable voltage reference source; a low frequency amplifier joined to the voltage reference source wherein the operating point of the amplifier depends on the voltage reference source that is biased for maximum allowable voltage swings of the amplifier; a first resistor connected in series with said low frequency amplifier which helps to set the gain in the low frequency amplifier; a GMI fiber that connects to the input of the low frequency amplifier, wherein the GMI fiber impedance varies with impressed magnetic fields when the fiber is excited by a radio frequency signal, which in turn varies an output voltage of the low frequency amplifier; a crystal oscillator connected in series to a second resistor and a first capacitor, wherein the crystal oscillator generates a square wave excitation signal with which to excite the GMI fiber, wherein the second resistor provides resistive damping, wherein the first capacitor alternating current couples the fiber excitation so that an additional direct current voltage from the oscillator does not build up across the GMI fiber; a decoupling network that allows stable excitation of the GMI fiber by separating the direct current paths of the low-frequency amplifier from the radio frequency excitation signal generated by the crystal oscillator; and an analog to digital converter that receives an output voltage from the low frequency amplifier and converts the output voltage to a digital signal.