The Scan Speed box lets you change the speed at which the CMM will scan the part. Depending on the state of the Display absolute speeds check box in the Part/Machine tab of the Setup Options dialog box, this will either be an absolute speed (mm/sec) or a percentage of the machine's defined top speed.
The Edit window command line for this option reads:
SCANSPEED/nnn.nnnn
Where nnn.nnnn is a number value for the speed.
When scanning using the DEFINED mode of execution (see "Defined" discussed in the "Exec Controls area" topic in the "Scanning your Part" chapter), Scan Speed plays an important role in getting back data at increments specified by you. When you specify a very high Scan Speed, the CMM may execute the scan at the speed you requested, but the data from the CMM may not be spaced at the increments you specify.
Assume the CMM gathers data at the rate of one Hit per 20 milliseconds in the DEFINED mode. If you specify an increment (minimum distance between hits) of 0.5 mm and a Scan Speed of 75 mm/sec, the CMM would give back points at every 1.5 mm. To avoid this you could reduce the Scan Speed to 15 mm/sec or 20 mm/sec which, at the rate of 1hit/20ms, would satisfy your requirements.
PC-DMIS will warn you about this case by displaying a message informing you that the supplied increment couldn't be measured at the specified scan speed. You will then be required to reduce your Scan Speed or increase the increment.
You can then select the Scan Speed setting and change to a suitable scan speed.