Interesting Problem - - -
I've been away from inspection for some time, and I only ever used a manual maching, so let me ask a couple of questions here.
1) Are these measures being taken manually or automatically?
2) Are the shafts on the two probes of different lengths?
It occurred to me that if the probe shafts are of different lengths and the measures are taken automatically then the measures may not be taken in the same location on the (presumably) Z axis.
3) Are the Probes "calibrated" on a ball for each use or is the dia's set in the software.
The thought here of course has to do with wear on the probes.
One other thought I had has to do with the probe design. Does the smaller probe have a tapered shaft? Is it possible that the shaft is hitting before the ball? I know it sounds rediculous but I'm just tossing out ideas.
Like I said - interesting problem.