Parallelism / sign at datum

[pcdmisstudent]

Hey guys
i have a parrallelism on a surface to datum A
and at the datum it has the symbol " / 100"
If i remember it correctly it has something to do with the tolerance zone, that its only per 100mm?
Can anyone explain this? And how should i do it in PC DMIS? Does normal parrallelism work?

[Schlag]

Post a picture of the callout. A specific callout per area / zone is legal on Flatness. I have never seen it on // before.

[louisd]

from ASME y14.5m 2009 spec

5.4.2.2 Applied on Unit Basis. Flatness may be
applied on a unit basis as a means of limiting an abrupt
surface variation within a relatively small area of the
feature. The unit variation is used either in combination
with a specified total variation, or alone. Caution
should be exercised when using unit control alone for
the reasons given in para. 5.4.1.3. Since flatness involves
surface area, the size of the unit area (e.g., a square area
25 25 or a circular area 25 in diameter) is specified to
the right of the flatness tolerance, separated by a slash.

Here's 5.4.1.3 for reference.

5.4.1.3 Applied on a Unit Basis. Straightness may be
applied on a unit basis as a means of limiting an abrupt
surface variation within a relatively short length of the
feature. See Fig. 5-4. When using unit control on a feature
of size, a maximum limit is typically specified to
limit the relatively large theoretical variations that may
result if left unrestricted. If the unit variation appears
as a “bow” in the toleranced feature, and the “bow” is
allowed to continue at the same rate for several units, the
overall tolerance variation may result in an unsatisfactory
part. Figure 5-5 illustrates the possible condition where
straightness per unit length given in Fig. 5-4 is used alone
(i.e., if straightness for the total length is not specified).