Patent ID: 6131301
Filing Date: 2000-10-17
Classification: G01B

Abstract:
A method of measuring dimensions of a workpiece using a coordinate positioning machine for causing relative movement between a measuring probe and the workpiece, the coordinate positioning machine having measuring devices for determining the positions of the movable machine parts during said relative movement, the probe having at least one signalling device from the output of which a trigger signal is generated when the probe achieves a predetermined position relative to a surface of the workpiece, said trigger signal being used to latch the readings of the measuring devices of the machine, the method comprising the steps of:establishing the components of the measurement error caused by the time delay between the probe reaching said predetermined position and the generation of the trigger signal,determining a mathematical functional relationship between said components and the relative velocity between the probe and the workpiece,performing a calibration to determine parameters of the mathematical functional relationship for a given probe configuration,storing the parameters,calculating from the outputs of the probe signalling device or devices and the machine measuring devices during a subsequent measuring process with the given probe configuration, the actual values of said relative velocity at least over a range of positions within which lies the position defined by the latched readings, andperforming correction calculations using the stored parameters and the calculated relative velocities in the mathematical functional relationship to correct the latched readings for velocity dependent errors.