Patent ID: 8468975

Claim:
A system for detecting the position of a portion of a laboratory animal, comprising: a first coil and a second coil aligned along a longitudinal axis, wherein a laboratory animal is placed on a floor located at approximately the mid point between the first and second coil; a resonant circuit attached to a portion of said laboratory animal, said resonant circuit defining a resonant frequency; a signal generator electrically coupled to said coil and configured to drive said at least one coil with at least a first drive signal comprising a first frequency and a second drive signal comprising a second frequency, wherein the second frequency is more distant from said resonant frequency than the first frequency; and a detection circuit coupled to said at least one coil and configured to detect an impedance change in said at least one coil between application of said first frequency to said at least one coil and application of said second frequency to said at least one coil, and to generate an output signal representative of resonant circuit position with respect to said at least one coil based at least in part on said impedance change.