what is tolerance limit for balance used on production floor for inprocess.
It is given in the USP, section <41> (I think)!
You wouldn’t use a microbalance on the floor, thus you have to scale the linearity of the balance to the potency of your drug product. In addition the standard calibration weights are S2-S3 as long as they are traceable (NIST in the USA).
I think tolerance limit to your production balance is to be decided based on criticality of its intended use. If balance used for weighing of input material or final product weighing and its least count is 0.001 kg i.e 10 g than tolerance should be 0.1% of std weight.
If its used to weigh wet cake during processing than tolerance can be 0.2% of std weight.