Algorithm Execution
Signal processing algorithms designed to calculate the angular displacement between a transmitted excitation signal and the received sensor signal provide a robust way to isolate material properties. This technique, referred to as phase angle extraction, is essential in electromagnetic testing because the phase shift is independent of sensor coil amplitude variations. The extracted angle can be mapped directly to a specific physical dimension such as coating thickness or metal conductivity.
Phase Calculation
The calculation relies on the output of a demodulator that provides in-phase and quadrature components. This ratio is used to determine the angle.
Calibration Routine
The instrument is calibrated by placing the probe on a series of reference standards with known properties. During phase angle extraction, the system software rotates the signal coordinates so that lift-off noise is aligned with a specific reference axis. This calibration step ensures that minor mechanical variations during the inspection do not corrupt the measurement.
Performance Metrics
The resolution of the phase measurement determines the sensitivity of the entire test instrument. Modern digital instruments can resolve differences as small as zero point zero one degrees under laboratory conditions. This high sensitivity is achieved by using low-noise analog input buffers and high-resolution converters.
