TESA MH3D, User Manual

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©2004 TESA Switzerland All Rights Reserved.
Page 3-16
User's Manual
MH3D
Measuring With an Electronic Probe
NOTE: Carefully read the probe user’s guide before attempting to use the probe.
Measurement points are recorded when the stylus is deflected enough to either
break mechanical contacts or generate enough force to trigger pressure sensitive
circuitry. This generates a signal to the controller, which latches the counters and
records the “point”. For manual measurements, the operator must be careful to
take measurement points at a velocity which will not create damage to the
probing system.
The arrangement of the contacts does cause slight errors in probing. These are
reduced during probe qualification. However, the longer the probe tip extension,
the larger the pre-travel error and the more residual error is left after probe
qualification. Also, longer probes tend to be not as stiff as shorter probes. The
more a stylus bends or deflects, the lower the accuracy. Therefore, probing with
very long stylus/extension combinations should be avoided.
Probe hits (also known as “points”) should be taken perpendicular to the part
surface wherever possible. If hits are not taken perpendicular to the part, skid-
ding may occur. Skidding (probe tip sliding on the part as probe contacts are
disturbed) produces inconsistent and non-repeatable results. If probe hits are
taken within 20 degrees of perpendicular, skidding errors will be much less than
one micron (0.000040 in.).
Note that probe approach
vectors are perpendicular
to the surface of the sphere
PART SURFACE
PROBE PATH
APPROACH OF THE PROBE
SHOULD BE WITHIN
±
80 °
OF THE PERPENDICULAR
POINT TO BE PROBED
Approach of the probe
should be within ±20°
of the perpendicular
Point to be probed
Probe path