Coordinate measuring machines gather data by means of a probe or sensor. Conventional CMMs equipped with touch-trigger probes can use a stitch-scanning method to record point streams from part surfaces. In stitch scanning, the CMM lifts the probe head from the surface of the part, moves it slightly forward and lowers it until contact is made for every data point collected. This single-point procedure is slow and unsuitable for efficient form measurement. Analog probes for continuous scanning are designed to send an uninterrupted stream of data back to a system computer. These probes avoid the time-wasting auxiliary movements required by point-to-point measuring probes.

Analog probes can be designed with solenoid systems, laser sensors or inductive displacement transducers. In the scanning process, the probe stylus is in constant contact with the part surface, and the measuring machine control system ensures that a consistent gaging force is maintained by detecting any deviations and regulating them immediately. This is called active probing, meaning that the force is constant regardless of the probe’s path. This force deflects the three probe axes, and high-resolution electronic transducers record the displacement. The dimensional data is read continuously from machine scales and analog probe transducers and analyzed by appropriate software.

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