Position Calculation

Position Calculation is performed automatically inside CambridgeIC’s CTU chips. Resonant inductive position sensors use ratiometric calculations for immunity to resonator Q-factor, supply voltage and component variations.

The sensor coils of a Type 1 sensor are patterned to produce a SIN/COS variation of coupling factor with changes in position. The calculation of position (Pr in the figure below) is equivalent to the calculation of phase angle, and is performed with a 4-quadrant inverse tangent.
Type 1 sensor position calculation

Changes in temperature, supply voltage, target Q-factor and component variations all tend to affect the SIN and COS signals equally.  This means they remain in the same proportion, and the reported position Pr remains the same.

Many other sensor types use a similar underlying calculation.