A capacitive encoder uses the change in capacitance value of a capacitor as a means to measure displacement. Typically, the capacitive sensor’s principle elements are arranged so that the capacitance changes as a moving elements displace relative to the stationary plates of the capacitor.
The capacitance effect is used in lots of sensors:
Capacitive encoders can offer high-resolution and accurate position measurement in benign environments. Capacitive encoders are, however, uncommon in safety-related applications because they can be sensitive to foreign matter or changes in temperature or humidity. The effect of condensation or buildup of electrostatic charge on a capacitive encoder can lead to misreporting of position.
Inductive encoders, such as IncOders from Zettlex are increasingly viewed as a suitable alternative to capacitive encoders – particularly for harsh environment applications, such as aerospace, medical, and oil & gas.