Patent ID: 8339129
Filing Date: 2012-12-25
Classification: G01H

Abstract:
1. An eddy current probe oscillator unit having a voltage input and a voltage output and arranged to be coupled to an eddy current probe, the eddy current probe oscillator unit comprising: a voltage input, and a voltage output, and a dual feedback loop including a first leg and a second leg, wherein the second leg is a voltage limiter that clips the voltage level at a predetermined maximum value used to create a defined voltage limited input that remains in phase with the output signal, wherein the voltage limiter is a high gain stage that ensures the voltage limiting and clipping during start up, wherein gain stages (a) and (b) that will, in combination with an output voltage divider R and a Zprobe impedance of the eddy current probe, ensure that overall feedback gain is unity and in-phase with the output signal, and wherein the eddy current probe oscillator unit is frequency independent and eliminates the need for parallel compensation inductors, that could change response over time.