Source: Content taken from a Powerpoint presentation used for conferences
Author: Mr. Ouellette
Date: 2001-02-12
Definitions
Calibration Interval
- Period of time or amount of use between calibrations
- To ensure equipment remains reliable
Reliable
- Within sufficient tolerance (or uncertainty) for the tests being done
Stakes
- Interval too short: Calibration $$$$
- Interval too long: Risk of bad measurements and repercussions
17025 Requirements
- [5.5.2] Equipment shall be:
- capable of achieving accuracy required
- comply with test/calibration method specifications
- managed under a calibration program
- Therefore, need to:
- define required accuracy
- identify the equipment that can affect it
- manage that equipment under a calibration program
- [5.6.1] Established program and procedure for calibration equipment (that matter).
- [5.1.1 et 5.1.2] Calibration program, etc., needs to consider many factors; e.g.
- human factors
- environmental
- sampling
- handling, etc.
CLAS Recommended Practices
- Calibration at (planned) periodic intervals to ensure acceptable accuracy and reliability
- Shorten intervals when results of previous calibrations suggest it
- May lengthen intervals on basis of demonstrated performance
- Documented procedure for assigning and adjusting calibration intervals
- Fully documented recall system
How to Establish Calibration Interval
- Consider influencing factors and existing knowledge, e.g.,
- accuracy sought and consequences of error
- manufacturer’s recommendations
- accommodation and environment
- purpose and usage
- maintenance and servicing
- trends from previous calibrations
- frequency of checks
- Make an initial choice, considering the factors above (especially the following ones):
- accuracy sought and consequences of error
- manufacturer’s recommendations
- accommodation and environment
- purpose and usage
- Monitor and review, adjust as necessary
- automatic or staircase method for individual item
- control chart (enables predictions)
- adjust based upon performance of a group of similar items
- in-service checks of critical parameters
References
- ILAC-G5: 1994 (www.ilac.org)
- ISO 10012-1: 1992 Annex A
- CLAS Recommended practices
- NCSL RP-1: 1996