Calibration for online machine inspection

Hmm.

Ok, it might be useful to know what kind of sorting machine it is and what kind of product?

Could you do some calibration yourself?  Or at least some checking to ensure the machine is reading accurately?

So for example, if it controls for weight, set up some packs at different weights including weights which should be rejected, use a calibrated scale (so the traceable to national standards part is covered) and test them through the machine?

The vision part is harder to trace to national standards but possible to test if you can make up test packs or test items which should be rejected (and it's safe to test in this way) much as you would for metal detector test packs.

One place I worked in we put stickers onto plastic covered cheese blocks to mimic mould presence to act as a test.  Not really calibration, more to check that the reject system was operational (so more monitoring) but it was the best we could do.

Other places have had calibration test "cards" which is more calibration.  These are things supplied by the manufacturer which set up distances, colours etc but I'm guessing you don't have those?

This gives a bit more info on the kinds of things that calibration might look for.

Machine Vision Annual Calibration - ProSensus - Multivariate Analysis Consulting for Manufacturing

Thinking about it, if you go back to the manufacturer and ask when they set it up did they check for things like shadows, light intensity, ability to detect items etc.  They may have calibrated it without realising that's what they're doing.  They may have even used a calibrated light meter in that test.  So their service report for that installation might cover what you need and ongoing servicing might be ok going forward.