Position Variance
Physical phenomena describe the change in sensor output that occurs as the distance between a transducer and a target increases. The lift off effect is a major source of error in eddy current and inductive sensing. This interaction is limited to the near field region of the sensor coil.
Signal Degradation
As the air gap grows, the magnetic coupling between the coil and the conductive material weakens. The lift off effect causes the amplitude of the signal to drop and the phase to shift. In non destructive testing, this can be mistaken for a change in material thickness or the presence of a flaw.
Maintaining a constant distance is necessary for high precision measurements.
Compensation Strategy
Advanced sensors use multi frequency excitation to separate the distance variable from the material properties. The lift off effect is mathematically modeled in the signal processor to neutralize its impact on the data. Reference curves are generated during calibration to define the relationship between distance and signal strength.
Some systems use a secondary sensor to measure the gap and provide real time correction.
Calibration Drift
Mechanical wear on the sensor face or the mounting bracket can lead to a gradual change in the resting gap. The lift off effect must be re-evaluated whenever the sensor is replaced or the mounting hardware is adjusted.
