Target Material Impact on Inductive Sensing Distance Reduction Factors
Target material conductivity and permeability set inductive sensing distance reduction factors, reducing nominal operating range by up to seventy percent.
Amplitude Demodulation
Signal Extraction
Extraction of information from a modulated carrier wave represents a fundamental process in high-frequency sensor signal chains. The implementation of amplitude demodulation allows a circuit to recover the envelope of a sensor signal, separating the high-frequency excitation frequency from the slower physical changes in target position. When a metallic target approaches an inductive coil, the high-frequency voltage across the sensor drops.
Processing this change requires stripping away the sinusoidal carrier to reveal the low-frequency modulation.
Circuit Design
Practical recovery of the modulating signal occurs through diode detection or synchronous rectification. An envelope detector built from a fast-recovery diode and a low-pass filter tracks the peak voltage of the carrier wave. The choice of filter capacitance determines the response time of the sensor.
If the filter discharges too slowly, high-frequency position changes are missed, whereas a discharge that is too fast introduces carrier ripple into the output.
Calibration Metric
Sensor precision depends on the linearity of the rectifier stage across the entire dynamic range. Standard references specify the extraction accuracy against a calibration curve generated by a known micrometer displacement. Signal distortion at low amplitudes limits the minimum sensing range.
Error Source
Thermal drift in the diode forward-voltage drop degrades the measurement stability over long run times. Compensating for this drift requires matched thermal-tracking diodes or active precision rectifiers. The resulting offset change must not exceed the target calibration limit.