Measuring instrument with arc encoder tracks

A method for operating a measuring instrument,

• the measuring instrument comprising:
• a movable portion which rotates in an arc motion about a pivot portion, the movable portion comprising a movable encoder portion, for which a maximum movement range of the arc motion of the movable encoder portion is less than 360 degrees;
• an electronic position encoder configured to measure an absolute relative position between a detector portion and a scale portion, wherein the movable encoder portion of the moveable portion comprises one of the detector portion or the scale portion, the electronic position encoder comprising:
• the scale portion extending along a scale direction, the scale portion comprising:
• a first scale element portion comprising first signal modulating scale elements;
• and
• a second scale element portion comprising second signal modulating scale elements;
• and
• the detector portion configured to be proximate to the scale portion with relative movement between the detector portion and the scale portion resulting from the arc motion of the movable encoder portion, the detector portion comprising:
• a field generating portion configured to generate changing magnetic flux in response to drive signals;
• and
• a sensing portion comprising:
• a first sensing element portion comprising a first set of first sensing elements and arranged in a first track portion with the first scale element portion;
• and
• a second sensing element portion comprising a first set of second sensing elements and arranged in a second track portion with the second scale element portion;
• the method comprising:
• providing the drive signals to cause the field generating portion to generate changing magnetic flux;
• and
• receiving detector signals from the detector portion, the detector signals comprising:
• detector signals from the first set of first sensing elements that operate in conjunction with first signal modulating scale elements, wherein the operating of the first set of first sensing elements in conjunction with first signal modulating scale elements includes the first set of first sensing elements providing the detector signals which respond to a local effect on a changing magnetic flux provided by first signal modulating scale elements of the first scale element portion;
• and
• detector signals from the first set of second sensing elements that operate in conjunction with second signal modulating scale elements, wherein the operating of the first set of second sensing elements in conjunction with second signal modulating scale elements includes the first set of second sensing elements providing the detector signals which respond to a local effect on a changing magnetic flux provided by second signal modulating scale elements of the second scale element portion,
• wherein:
• the first and second scale element portions of the first and second track portions are arc-shaped and are parallel to each other, with the second track portion closer to the pivot portion than the first track portion;
• and
• the first signal modulating scale elements are disposed along the first scale element portion according to a first signal modulating element angular spatial step θWSME1 and the second signal modulating scale elements are disposed along the second scale element portion according to a second signal modulating element angular spatial step θWSME2 that is different than the first signal modulating element angular spatial step θWSME1.

An electronic position encoder configured to measure an absolute relative position between a detector portion and a scale portion and to be utilized in a measuring instrument that comprises a movable portion configured to rotate in an arc motion, the electronic position encoder comprising:

• the scale portion extending along a scale direction, the scale portion comprising:
• a first scale element portion comprising first signal modulating scale elements;
• and
• a second scale element portion comprising second signal modulating scale elements;
• and
• the detector portion configured to be proximate to the scale portion with relative movement between the detector portion and the scale portion resulting from the arc motion of the movable portion, for which a maximum movement range of the arc motion is less than 360 degrees, the detector portion comprising:
• a field generating portion configured to generate changing magnetic flux in response to drive signals;
• and
• a sensing portion comprising:
• a first sensing element portion comprising a first set of first sensing elements and arranged in a first track portion with the first scale element portion;
• and
• a second sensing element portion comprising a first set of second sensing elements and arranged in a second track portion with the second scale element portion;
• wherein:
• the first and second scale element portions of the first and second track portions are arc-shaped and are parallel to each other, with the second track portion closer to the pivot portion than the first track portion;
• and
• the first signal modulating scale elements are disposed along the first scale element portion according to a first signal modulating element angular spatial step θWSME1 and the second signal modulating scale elements are disposed along the second scale element portion according to a second signal modulating element angular spatial step θWSME2 that is different than the first signal modulating element angular spatial step θWSME1;
• and
• wherein at least one of:
• the first scale element portion is arranged with a centerline at a first radius RD1 from the pivot portion and the second scale element portion is arranged with a centerline at a second radius RD2 from the pivot portion, for which the first radius RD1 is larger than the second radius RD2;
• or
• the first sensing element portion further comprises one or more additional sets of first sensing elements, for which each additional set of first sensing elements has a spatial phase offset relative to the first set of first sensing elements, and the second sensing element portion further comprises one or more additional sets of second sensing elements, for which each additional set of second sensing elements has a spatial phase offset relative to the first set of second sensing elements.