Also called traceability, NRC traceable, calibration certificate, out of tolerance
What is calibration?
Checking a measuring instrument against a known standard, on a schedule, and keeping the record.
What else it is called
- Other names
- traceability, NRC traceable, calibration certificate, out of tolerance
- In French
- étalonnage
Related entries
Understanding calibration
An instrument is compared against a reference of known accuracy, the difference is recorded, and the instrument is either accepted, adjusted or taken out of service. The chain of references runs upward: your gauge block is checked against a better standard, which is checked against a better one again, ending at a national measurement institute. In Canada that is the National Research Council, and the phrase you will see on a certificate is traceable to NRC.
The part plants under-plan for is what happens after a failed calibration. If a caliper is found reading 0.08 millimetres high, every part it passed since its last good check is in question. A real procedure says who decides, how far back you look, and how customers get told. Discovering that you have no such procedure on the day it happens is an expensive way to learn.
In practice
Keep the out-of-tolerance procedure written and agreed before you need it. The decision about six weeks of shipped product should not be made at four o’clock on a Friday by whoever is still in the building.
Frequently asked
How often should instruments be calibrated?
Based on how much they are used, how roughly, and what they are used to decide, not on a single blanket interval. A daily-use caliper on a critical dimension needs checking far more often than a shelf instrument used twice a year, and intervals should move when history shows drift.
What does traceable to NRC mean?
That the chain of comparisons behind your instrument ends at Canada’s national measurement institute, the National Research Council, with each link documented. It is what lets a customer or auditor trust a number produced in your plant.