A calibration certificate is the documentation from a completed calibration. It should identify the right instrument, show what was measured and how the result compares with the reference – so you can review it and find it again at audit.
Here is what the certificate usually includes, how to review it when it comes back, what ISO 9001 says about the records, and how to keep them in order. How often an instrument should be calibrated belongs in a separate article: calibration intervals under ISO 9001.
The overview of tool and measuring-instrument calibration is on the owner page.
What is a calibration certificate?
In short: the record from the lab (or whoever calibrated the instrument) that a comparison against a reference has been made.
- Calibration measures what the instrument shows at set points compared with the reference.
- Adjustment is when someone then corrects the instrument. That is not the same as the calibration itself.
- Verification is often used when you check that the instrument still sits within your tolerance, without a full calibration.
Calibration certificate, calibration report and similar names are used interchangeably. The point is the same: documentation tied to the right instrument.
What should a calibration certificate include?
Exactly which fields appear is driven mainly by the lab and the job. Accredited calibration laboratories work under the reporting requirements in ISO/IEC 17025. When you receive the certificate, it is practical to check that the following are present:
- the instrument ID or serial number
- make and model, when stated
- which sensors or measurement channels are covered
- calibration date and the certificate's unique identifier
- per measurement point: reference value, instrument reading and deviation
- measurement uncertainty
- information on the reference equipment and traceability
- any agreed tolerance and conformity assessment, if that was part of the job
- who performed and who authorised the work, when stated
A certificate does not automatically mean the instrument is "approved". Without a requirement or tolerance to compare against, it is mainly a record of what was measured.
How do you review the certificate when it comes back?
Go through it before the instrument returns to service:
- Does the ID match? Serial number and instrument ID should match what you sent in.
- Right scope? Sensors, channels and points as ordered.
- Deviation and uncertainty. Compare the deviation with your tolerance. Include measurement uncertainty in the assessment when relevant.
- Outside tolerance? Take the instrument out of use until you decide on action. Assess whether earlier measurements may have been affected – that is your routine, not the lab's.
Keep both the certificate and your own assessment. Then you have the evidence when the auditor asks.
What does ISO 9001 say about calibration certificates?
ISO 9001:2015 addresses monitoring and measuring resources in clause 7.1.5. Clause 7.1.5.2 covers measurement traceability.
In short, 7.1.5.2 is about making sure measuring equipment is calibrated or verified at set intervals or before use, with traceability to international or national measurement standards, that its status can be identified, that it is protected against adjustment, damage and deterioration, and that you act if the equipment turns out to be unsuitable for its intended purpose – including checking whether earlier results were affected. This is our own summary, not a quotation from the standard. The ISO 9001 Auditing Practices Group guidance on measurement traceability notes that clause 7.1.5.2 applies "when measurement traceability is a requirement, or is considered by the organization to be an essential part of providing confidence in the validity of measurement results" (ISO APG – Measurement Traceability).
ISO's guidance on documented information lists, among other things, that the organisation shall retain:
- "Evidence of fitness for purpose of monitoring and measuring resources (clause 7.1.5.1)"
- "Evidence of the basis used for calibration of the monitoring and measurement resources (when no international or national standards exist) (clause 7.1.5.2)"
In practice the calibration certificate is often the record you show so that status and results can be followed. The standard does not say how you must store it – only that relevant documented information must exist and be controlled.
How long should you keep calibration certificates?
ISO 9001:2015 does not state a fixed retention period in years for calibration certificates in the guidance we rely on. The organisation decides how long the records are needed.
In practice, contracts, customer requirements, sector rules or product lifetime may set the period. Write your own retention time into your routines so you give the same answer at audit.
Where should certificates be stored so they can be found at audit?
The goal is simple: the certificate should sit with the right instrument.
Paper in a binder works if you can find the right sheet in a few seconds. Digitally, it is natural to keep the certificate with the instrument's other details – status, dates and other documents – so the auditor sees the same picture you do.
In Delatool you can upload a calibration certificate as an attachment on a calibration activity in the Activity centre, or as a document on the tool profile in Tool management. Allowed attachment formats for the activity are JPG, PNG, WebP, GIF and PDF.
Delatool stores calibration activities per tool with attachment and status. Current activities and uploaded documents are shown directly on the tool.
For an audit, you pull the evidence in the Activity centre (status, next date and activity attachments) and any documents on the tool profile.
Mark instruments so status is visible on the shop floor, for example by marking measuring instruments with a QR code. When needed you can also take stock of your tools so no instrument with a calibration requirement is missing from the register.
More on tool and measuring-instrument calibration and the tool management system.
Frequently asked questions
Does Delatool perform the calibration? The calibration itself is done by your lab. Delatool keeps the register, intervals, reminders and certificates – Delatool does not calibrate and is not an accredited calibration laboratory.
Does the lab have to be accredited? It depends on your own requirements, your customers' requirements and any sector rules. ISO 9001 requires traceability where applicable, but we are not stating a general legal duty of accreditation here. Check what applies to your business.
Is the certificate enough to prove the instrument is approved? Not by itself. You need a tolerance or requirement to compare the result against, and your own assessment.
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Questions? Email info@delatool.com.
