Zeiss CONTURA, Operating Instructions Manual

Page: 119 / 158

Evaluation of the measured results
61211-1310402 CONTURA
7-23
Evaluation of the measured results
Limit values for deviations
Standard deviation
The result is evaluated according to the standard deviation. There is no
maximum standard deviation which applies to all applications. The toler-
able deviation depends on many factors: for example resolution and pre-
cision of the CMM, length and rigidity of the stylus shaft, quality of the
stylus tip, cleanness of the environment, surface and form of the work-
piece.
It may be necessary to decide whether or not to tolerate measuring in-
accuracies.
Causes of scattering and measurement errors
The sources of malfunctions and errors which may lead to increased de-
viations are listed below.
Source of error Cause
Home position – No reference measurement has been carried out.
Temperature compensation – No temperature compensation performed.
– Incorrect temperature compensation, for example a wrong material
coefficient has been entered.
Status of the reference
sphere and of the stylus
system – The setup of the reference sphere is not stable.
– The reference sphere or stylus tip is soiled, oiled or damaged.
– The stylus system components or adapter plate are/is damaged.
Reference sphere holder – The bottom side of the reference sphere holder is damaged.
– The tightening torque is too high or too low.
Stylus system configuration – The structure of the stylus system is not stable.
– The stylus system components are not screwed together firmly
enough.
– Admissible probe limiting values have not been observed.
The stylus system is too long, too heavy or contains components
which are not suitable.