Method and apparatus for determining the rotary angular position of a rotary member when measuring unbalance

A method of determining the rotary angular position of a segmented rotary member when measuring the unbalance of said segmented rotary member, said segmented rotary member having a plurality of segments, said method comprising the steps of:

• determining an angular position of a measured unbalance of said segmented rotary member;
• a first sensing step in which each of said plurality of segments of the segmented rotary member are sensed from a first sensing position in succession with respect to time during an unbalance measuring run;
• a second sensing step in which each of said plurality of segments of the segmented rotary member are sensed from a second sensing position in succession with respect to time during the unbalance measuring run, said second sensing step occurring simultaneously with said first sensing step, said first and second sensing positions being spaced apart by an angular distance comprising a distance which is less than an angular distance subtended by each of said plurality of segments plus an integer multiple of an angular distance between corresponding points on adjacent ones of said plurality of segments;
• forming, in each revolution of the segmented rotary member, first and second angle signals during said first and second sensing steps, respectively, lack of said first and second angle signals having characteristic to each of said plurality of segments of the segmented rotary member and an angular spacing between each of said plurality of segments, said first and second angle signals being phase shifted from one another with respect to time;
• storing the first and second angle signals having regard to the phase shifted spacing between said first and second angle signals;
• evaluating the first and second angle signals;
• and
• rotating the rotary member into an angular balancing position for a balancing operation in response to said evaluation step and in dependence on the measured angular position of unbalance.