| 摘要 |
A method of determining the position of a probe relative to a scale wherein the probe contains a sensor of the type comprising one or more pairs of orthogonal sensing elements X, Y operable to measure properties varying locally with the position of the probe relative to the scale. In use, a sinusoidally varying bias Ix, Iy is applied to each of the elements X, Y. The resultant outputs of elements X and Y are fed to summing means 101 and difference means 102. The summing means 101 is operable to output a summed signal Vsum equal to the instantaneous sum of Vx and Vy. The difference means 102 is operable to output a difference signal Vdiff equal to the instantaneous difference between Vx and Vy. The outputs Vsum and Vdiff are fed into a phase comparator 103, which is operable to determine the phase difference between them. The phase angle between Vsum and Vdiff provides an indication of the position of the probe relative to the scale. In alternative embodiments the phase angle between either Vsum or Vdiff and the bias signal may be used to Vdiff provides an indication of the position of the probe relative to the scale. In various embodiments, the above method is applied to both linear and rotary systems using magnetic or optical sensing elements.
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