Vision system calibration standard- need for annual recertification?

[AnalogKid2DigitalMan]

Hello All:

 

Questions and guidance regarding chrome-on-fused silica targets used to calibrate vision systems:

 

We have a couple of these at our facilities and in order to satisfy ISO requirements, some people internally insist these must be sent out yearly to be ‘calibrated’ (re-certified is probably a better term). Since they are not subject to wear akin to rulers, scales, pin/plug gauges, I see no need to have this done. They are a pattern of squares and circles of various sizes, typically ranging from 0.0005” to 0.5” and have been measured at the time of manufacture to within +/-.00001” and 0.00002” uncertainty. Coefficient of expansion is a negligible 0.5ppm/C. Unfortunately, the companies that fabricated and measured the standards (P.P.L/Align-Rite and Optronics Specialty) have moved on to other lines of work and I cannot get a statement from them to back up my position. The last time we sent one out, it almost was lost in transit and then took 3 months to get it back.

 

Anyone else have experience with such matters and how did you handle it?

Other than NIST, any suggestions of companies that can certify such standards since I would like to get a tighter uncertainty measurement on one of the standards.

 

Thanks for your feedback!

 

-AK2DM

Message Edited by AnalogKid2DigitalMan on 10-14-2008 08:46 AM

[muks]

I faced the same problem.I used a measurement target initially and before getting into action we wanted to recheck it. It was a bit of a frustration but as luck would have it we have top grade measurement instruments that will measure and differentiate 1 micron (That is more than sufficient).So i used a metal strip and measured it and took that as the reference