What a calibration certificate is
A calibration certificate records that an instrument, such as a pressure gauge, transducer, thermometer or torque wrench, was compared against a reference standard, and what was found. It is issued by a calibration laboratory or your own calibration function. On engineered-equipment orders, the test reports name the instruments used, and the certificates prove those readings can be trusted.
What a certificate should contain
- The instrument's identity: maker, model, serial number or asset ID.
- The calibration date, and often a due date or interval.
- The points or range calibrated, the readings found and, where adjusted, the readings after adjustment.
- The measurement uncertainty, on most laboratory certificates.
- The reference standards used and their traceability to national or international standards.
- The laboratory's name and, where it has one, its accreditation, for example to ISO/IEC 17025.
- A signature or authorisation, and a certificate number.
Four checks against each test
| Check | What passes | Common failure |
|---|---|---|
| Identity | The serial or asset ID on the test report matches the certificate | Report says "gauge 0–400 bar" with no ID |
| Date | The test date falls inside the calibration validity | Certificate expired a week before the test |
| Range | The values measured sit inside the calibrated range | Test at a pressure above the highest calibrated point |
| Traceability | The certificate traces to a national or international standard | In-house check with no traceable reference |
Customer specifications can add more, such as an accredited laboratory, a maximum calibration interval or a gauge range rule. Read the order's quality clauses and the approved test procedure.
What ISO 9001 expects
ISO 9001, in its clause on monitoring and measuring resources, expects instruments used to verify product to be calibrated or verified at set intervals against standards traceable to national or international standards, identified so their status is clear, and protected from adjustments that would spoil the result. If an instrument is found out of calibration, you must check whether earlier results are still valid. Read the standard itself for the exact wording.
When an instrument is found out of calibration
List every test that used the instrument since its last good calibration. Assess whether the error could have changed a pass to a fail. Tell the customer where their tests are affected, and repeat tests where needed. Record it as a nonconformance. Finding this after shipment is far worse than before the witness test.
Check before the witness test
- List the instruments each test procedure needs, by ID.
- Check each certificate is in date on the planned test date, with a margin if the date might slip.
- Check the range suits the test values in the procedure.
- Put copies of the certificates with the test pack for the inspector.
- Write the instrument IDs on the test record sheet before the test starts.
This is part of factory acceptance test (FAT) preparation. The certificates then go into the calibration section of the manufacturing record book.
Doing it with OdysseyGPT
The Calibration Validity Check (beta) matches each instrument on your test reports to its calibration certificate by identity, then checks validity on the date of use, range and the traceability chain, and flags certificates about to expire. Every finding cites the report and the certificate. A quality engineer decides what to do with each one.
These tools are in beta
The Calibration Validity Check are in beta. You can request access, and we onboard each team ourselves. Every finding cites the page, sheet or cell it came from, and your engineers decide what to do with it.