POSITION SENSOR
First Claim
1. 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 operable to measure properties varying locally with the position of the probe relative to the scale, the method comprising the steps of:
- applying a periodically varying bias to each sensing element;
determining the sum of and/or the difference between the outputs of pairs of sensing elements to provide a sum output signal and/or a difference output signal for each pair of sensing elements; and
determining one of;
the phase difference between the sum and difference output signals;
the phase difference between the sum output signal and the applied bias;
or the phase difference between the difference output signal and the applied bias for each pair of sensing elements to thereby determine the position of the probe relative to the scale.
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Accused Products
Abstract
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.
37 Citations
28 Claims
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1. 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 operable to measure properties varying locally with the position of the probe relative to the scale, the method comprising the steps of:
- applying a periodically varying bias to each sensing element;
determining the sum of and/or the difference between the outputs of pairs of sensing elements to provide a sum output signal and/or a difference output signal for each pair of sensing elements; and
determining one of;
the phase difference between the sum and difference output signals;
the phase difference between the sum output signal and the applied bias;
or the phase difference between the difference output signal and the applied bias for each pair of sensing elements to thereby determine the position of the probe relative to the scale. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
- applying a periodically varying bias to each sensing element;
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11. A position sensor for sensing the position of a probe relative to a scale comprising:
- one or more pairs of sensing elements;
bias generating means operable to apply a periodic bias to each sensing element;
one or both of summing means for calculating a sum output signal for each pair of sensing elements the sum output signal being the sum of the outputs of the pair of sensing elements and difference means for calculating a difference output signal for each pair of sensing elements the difference output signal being the difference between the outputs of the pair of sensing elements; and
phase comparator means for determining one of;
the phase difference between the sum and difference output signals;
the phase difference between the sum output signal and the applied bias;
or the phase difference between the difference output signal and the applied bias for each pair of sensing elements to thereby determine the position of the probe relative to the scale. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
- one or more pairs of sensing elements;
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21. A method of removing inherent offset from an output signal of a Hall element of the type having a pair of biasing contacts (designated supply negative SN and supply positive SP) and a pair of output contacts (designated output negative ON and output positive OP), the method comprising the steps of:
- commutating connection to the contacts such that each of the contacts is operable as each of the pair of bias contacts SN, SP and operable as each of the output contacts ON, OP in a regular cycle; and
applying a suitable filter to the obtained output such that the element due to the inherent offset signal is substantially removed but the element due to the true Hall output signal is substantially retained. - View Dependent Claims (22, 23, 24, 25, 26, 27)
- commutating connection to the contacts such that each of the contacts is operable as each of the pair of bias contacts SN, SP and operable as each of the output contacts ON, OP in a regular cycle; and
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28. An offset removal circuit for removing inherent offset from an output signal of a Hall element of the type having a pair of biasing contacts (designated supply negative SN and supply positive SP) and a pair of output contacts (designated output negative ON and output positive OP), the circuit comprising:
- commutation means operable to apply a commutation cycle to the contacts;
means for applying a bias current to the currently operable bias contacts;
means for receiving an obtained output signal from the currently operable output contacts; and
filter means for applying a filter to the obtained output signal such that such that the element due to the inherent offset signal is substantially removed but the element due to the true Hall output signal is substantially retained.
- commutation means operable to apply a commutation cycle to the contacts;
Specification