I am wondering if ther is some sort of calculation to the frequency of calibrating scales. We do not use them in high volume and are on a 6 month calibration. I am not sure that this is feasible. Anyone have any thoughts?!

Ours is also on a 6 month shedule... never been a problem. We do them right before our year end inventory and again during a July shutdown.

I am wondering if ther is some sort of calculation to the frequency of calibrating scales. We do not use them in high volume and are on a 6 month calibration. I am not sure that this is feasible. Anyone have any thoughts?!

Calibration intervals should be based on experience. If, when devices are calibrated, it's found that they need significant adjustment, intervals should be shortened. Conversely, if no significant adjustments are needed, you might be justified in extending the intervals. It's not a good idea to set intervals arbitrarily.

We're at 6 months for shipping scales, etc. One reference to check is NIST Handbook 44, Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices. It is viewable online at: http://ts.nist.gov/ts/htdocs/230/235/h442003.htm

The other question to ask is if you decrease your calibration, and you discover you were out of calibration, investigated and found possible non-conforming product shipped to your customer(s), and were then required to notify your customer(s), what effect would that have on your business on a long term basis?

Another source to consider is RP-1 (Recommended Practice) from NCLSI (National Conference of Standards Laboratories - International).

http://www.ncsli.org

It is the RP that provides guidance for establishing cal intervals.

Hershal

ozziegood,
When I worked as a cal tech we always used a 10% rule - that is increase or decrease cal intervals by 10%. That way you don't find yourself giving the scales an extra 6 months, pushing the cal out to a year, only to find they failed at 7 months.

Some good advice has already been stated. Base your frequency on experience. More important is to maintain a verification scheme that allows you to quickly and frequently check your scales and balances. That way you don't get surprises and you maintain confidence in your measurements in between calibrations.