Linear position measuring system and method for determining the absolute position of a carriage along a slide rail

A linear position measuring system for determining an absolute position of a carriage along a slide rail, with a reference scale placed along the slide rail and a scanner secured to the track carriage, wherein the scanner is designed to scan reference points along the reference scale, wherein the reference points are scanned as an essentially analog signal progression (S), which consists of sequential first and second signal half-wave progressions (S1, S2), characterized in that the linear position measuring system further encompasses:

• a) at least one threshold storage device for storing a first and second threshold (SW1, SW2), whose levels are varyingly adjustable relative to each other,
• b) a first comparator for comparing the scanned values of the first signal half-wave progression (S1) with the first threshold (SW1) in a sectional interval of the first signal half-wave progression (S1), and to output:
• those scanned values of the first signal half-wave progression (S1) that are less than the first threshold (SW1) to a first measured value register (MR1) for storing those values as a first discrete SW1 half-wave bit value, and
• those scanned values of the first signal half-wave progression (S1) that are greater than the first threshold (SW1) to the first measured value register (MR1) for storing those values as a second discrete SW1 half-wave bit value,
• c) a second comparator for comparing the canned values of the second signal half-wave progression (S2) with the second threshold (SW2) a sectional interval of the second signal half-wave progression (S2), and to output:
• those scanned values of the second signal half-wave progression (S2) that are less than the second threshold (SW2) to a second measured value register (MR2) for storing those values as a first discrete SW2 half-wave bit value, and
• those scanned values of the second signal half-wave progression (S2) that are greater than the second threshold (SW2) to the second measured value register (MR2) for storing those values as a second discrete SW2 half-wave bit value,
• d) a first set measured value register (MRsoll1) for storing set measured values for the values in the sectional interval of the first signal half-wave progression (S1), and a second set measured value register (MRsoll2) for storing set measured values for the values in the sectional interval of the second signal half-wave progression (S2), wherein the measured value registers (MR1, MR2) and set measured value registers (MRsoll1, MRsoll2) exhibit an identical bit length,
• e) at least one logical comparison module for comparing the respective contents of the first and second measured value register (MR1, MR2) with the contents of the first acrd second set measured value register (MRsoll1, MRsoll2), and for outputting a differential value from this comparison, and
• f) a tolerance range comparator for comparing the differential value with a predetermined tolerance range, and, based on this comparison, to acquire and output each reference point (20) as an ideal reference point if the differential value lies within a predetermined tolerance range.