Calibration of step gauges and length bars

Published with permission from NPL

AcWaCo configurations are available for three different ranges.

Short range (< 600 mm): Transducers (200 kHz) are placed on the interferometer. The sound waves are reflected from the mirror on the probe.
Medium range (< 1200 mm): Transducers (200 kHz) are placed on the interferometer and the mirror on the probe.
Long range (e.g. 2000 mm): Transducers (50 kHz) are placed on the interferometer and the mirror on the probe.

Renishaw, Applicatiоn example

The laser interferometer measurement, done at the moment when the probe touches the step gauge, is immediately and transparently compensated for environmental errors by AcWaCo.

There are two laser beams in order to eliminate the Abbé offset error. The speed of sound is measured along both laser beams and AcWaCo calculates the compensation factor for each beam. This way the environmental error is virtually eliminated. Therefore the system is free from dead-path error, Abbé error and environmental errors.

Another example of this application may look like this:

Because the position measurement is done by the laser interferometer, the CMM is only used as a manipulator.