Choosing calibration points
Calibrate where you measure. Points should bracket the use range and include any temperature where a decision is made.
- Cover the range of use, including both ends; do not extrapolate beyond the calibrated points.
- Include the specific temperatures at which the instrument makes decisions — alarm limits, storage set points.
- Use enough points to reveal non-linearity; three is a minimum for a simple sensor, more for wide ranges.
- For PRTs, include or approach 0 °C where a known reference point exists.
- Match the medium and immersion to service conditions where practical.
A logger used only in a 2–8 °C refrigerator does not benefit from a certificate at 25 °C and 50 °C; it needs points at and around its limits.
Frequently asked questions
- What calibration points should a 2–8 °C logger have?
- Typically around 2, 5 and 8 °C, or slightly wider (0, 5, 10 °C) so the use range is bracketed and the alarm limits are covered.
- What calibration points for a −20 °C freezer logger?
- Points that bracket the storage condition, for example −25, −20 and −15 °C, plus any alarm limit temperature.
References
- [1]ISO/IEC 17025:2017 — General requirements for the competence of testing and calibration laboratories
- [2]EURAMET cg-20: Calibration of Climatic Chambers
General technical guidance written against the cited sources. It is not regulatory or legal advice and does not replace the applicable standard, guideline or a qualified reviewer's judgement.
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