An electronic position encoder usable to measure a relative position between two elements along a measuring axis direction, the electronic position encoder comprising:
- a scale extending along the measuring axis direction which includes a periodic scale pattern comprising at least a first type of signal modulating elements that include an effective region that is aligned with or overlaps an interior area of a field generating coil, wherein the periodic scale pattern has a spatial wavelength W1 and signal modulating elements of the first type comprising conductive plates or conductive loops that are located along the measuring axis direction corresponding to the spatial wavelength W1;
- a detector portion configured to be mounted proximate to the periodic scale pattern and to move along the measuring axis direction relative to the periodic scale pattern, the detector portion comprising:
- the field generating coil fixed on a substrate, the field generating coil surrounding the interior area that is aligned with the effective region of the periodic scale pattern of signal modulating elements during operation, the field generating coil configured to generate a changing magnetic flux in the interior area in response to a coil drive signal;
- a first respective set of sensing elements corresponding to a first respective nominal spatial phase, arranged along the measuring axis direction and fixed on the substrate, members of the first respective set of sensing elements comprising conductive loops that respectively define a sensing element effective area EffASEN corresponding to a portion of a respective one of the sensing elements that is aligned with or overlaps the interior area, wherein the first respective set of sensing elements are configured to provide respective detector signals of the first respective set of sensing elements which respond to a local effect on a changing magnetic flux related to the signal modulating elements of the scale pattern which are adjacent to the first respective set of sensing elements, and which correspond to the first respective nominal spatial phase;
- and
- a second respective set of sensing elements corresponding to a second respective nominal spatial phase that is 90 degrees different from the first nominal spatial phase of the first respective set of sensing elements, wherein the second respective set of sensing elements are configured to provide respective detector signals of the second respective set of sensing elements which respond to a local effect on a changing magnetic flux related to the signal modulating elements of the scale pattern which are adjacent to the second respective set of sensing elements, and which correspond to the second respective nominal spatial phase;
- and
- a signal processing configuration arranged on a substrate, wherein the signal processing configuration is operably connected to the detector portion to provide the coil drive signal and is configured to determine a relative position between the detector portion and the scale pattern based on the respective detector signals of the first and second respective sets of sensing elements which are input from the detector portion,
- wherein the first respective set of sensing elements corresponding to the first respective nominal spatial phase comprises features A1, B1 and C1, defined as follows:
- A1) a number of positive polarity loops corresponding to a first winding direction or polarity and the same number of negative polarity loops corresponding to a second winding direction or polarity opposite to the first winding direction or polarity;
- B1) for each of the positive and negative polarity loops, the sensing element effective area EffASEN is defined to have an effective y-axis dimension EffYSEN along a y-axis direction that is the dimension of the interior area perpendicular to the measuring axis direction, and least a majority of the positive and negative polarity loops are configured to provide a sensing element average dimension DSENavg=(EffASEN/EffYSEN) along the measuring axis direction that is within a range 0.33*W1+/−15%;
- and
- C1) the positive polarity loops are configured with their sensing element effective areas arranged in a positive polarity loop prescribed relationship relative to the first respective nominal spatial phase of the first respective set of sensing elements, and the negative polarity loops are configured with their sensing element effective areas arranged in a negative polarity loop prescribed relationship relative to the first respective nominal spatial phase of the first respective set of sensing elements, wherein:
- a total sensing element effective area of the number of positive polarity loops is a sum of the sensing element effective areas of the number of positive polarity loops, and
- a total sensing element effective area of the number of negative polarity loops is a sum of the sensing element effective areas of the number of negative polarity loops
- the positive polarity loop prescribed relationship comprises a configuration wherein a shifted proportion of up to half of the total sensing element effective area of the number of positive polarity loops is shifted along the measuring axis direction in a first direction by an amount (W1)/4K in relationship to the first respective nominal spatial phase, and nominally the same shifted proportion of the total sensing element effective area of the number of positive polarity loops is shifted along the measuring axis direction in a direction opposite to the first direction by an amount (W1)/4K in relationship to the first respective nominal spatial phase, such that the two shifted proportions of the total sensing element effective area of the number of positive polarity loops are shifted by (W1)/2K relative to one another, wherein K is one of 3, 5, 7 or 9;
- and
- the negative polarity loop prescribed relationship comprises a configuration wherein a shifted proportion up to half of the total sensing element effective area of the number of negative polarity loops is shifted along the measuring axis direction in a first direction by an amount (W1)/4K in relationship to the first respective nominal spatial phase, and nominally the same shifted proportion of the total sensing element effective area of the number of negative polarity loops is shifted along the measuring axis direction in a direction opposite to the first direction by an amount (W1)/4K in relationship to the first respective nominal spatial phase, such that the two shifted proportions of the total sensing element effective area of the number of negative polarity loops are shifted by (W1)/2K relative to one another;
- further comprising a feature E1, defined as follows:
- E1) the first respective set of sensing elements corresponding to the first respective nominal spatial phase is configured in a two-portion configuration comprising:
- a first separated portion comprising a same number of positive polarity loops and negative polarity loops;
- and
- a second separated portion that is aligned along the measuring axis direction with the first portion, and that comprises the same number of positive polarity loops and negative polarity loops as the first separated portion,
- wherein the first and second separated portions are separated by a gap located along the measuring axis direction between the first portion and the second portion, wherein the gap is at least as wide along the measuring axis direction as one of the positive or negative polarity loops and no positive polarity loop effective area or negative polarity loop effective area of the first respective set of sensing elements is located in the gap;
- and
- whereby the first respective set of sensing elements corresponding to the first respective nominal spatial phase is configured to reduce or suppress at least one of an unwanted 3rd spatial harmonic detector signal component and or an unwanted Kth spatial harmonic detector signal component, that would otherwise contribute to error in the determined relative position between the detector portion and the scale pattern;
- and
- wherein:
- the second respective set of sensing elements comprises:
- the features A1, B1 and C1;
- a first portion comprising a same number of positive polarity loops and negative polarity loops;
- and
- a second portion that is aligned along the measuring axis direction with the first portion, and that comprises the same number of positive polarity loops and negative polarity loops as the first portion;
- a total sensing element effective area of the first respective set of sensing elements is a sum of the sensing element effective areas of the first respective set of sensing elements;
- the first respective set of sensing elements has a first area centroid of its total sensing element effective area located along the measuring axis between its first and second separated portions;
- a total sensing element effective area of the second respective set of sensing elements is a sum of the sensing element effective areas of the second respective set of sensing elements;
- the second respective set of sensing elements has a second area centroid of its total sensing element effective area located along the measuring axis between its first and second portions;
- and
- the first and second respective sets of sensing elements are arranged with their respective first and second area centroids located at a same location along the measuring axis direction.