Reliable laboratory measurements depend not only on good equipment but also on knowing how that equipment performs against suitable reference standards. A calibration certificate documents the conditions and results of a calibration.
What Is Calibration?
Calibration establishes, under specified conditions, the relationship between values indicated by measuring equipment and values obtained from traceable reference standards.
Calibration should not be confused with adjustment. Calibration determines measurement performance; it does not necessarily change or adjust the instrument.
What Does a Calibration Certificate Contain?
Depending on the calibration, it may include:
- Equipment identification
- Manufacturer, model and serial number
- Calibration date
- Calibration method
- Environmental conditions where relevant
- Reference standards
- Measurement results
- Measurement uncertainty
- Metrological traceability information
- Certificate number
- Calibration laboratory information
When Is It Required?
Calibration becomes particularly important when measurement results directly influence analytical or quality decisions.
Typical examples include:
- Volumetric pipettes
- Burettes
- Volumetric flasks
- Automatic pipettes
- Balances
- Thermometers
- pH meters
Laboratories operating under ISO/IEC 17025 must ensure that equipment affecting measurement results is suitable for its intended purpose and establish metrological traceability where required.
Is a Class A Product Automatically Supplied with a Calibration Certificate?
No.
Class A refers to defined tolerances under the applicable product standard. It does not automatically mean that each individual product has an accredited calibration certificate.
Therefore:
Class A ≠ Individual Calibration Certificate
The same distinction should be considered for Class AS volumetric glassware.
Batch vs Individual Certificates
A batch certificate relates to a defined production batch and the manufacturer's applicable batch-control system.
An individual certificate identifies and documents a specific item.
The appropriate option depends on the application and quality-system requirements.
What Is Metrological Traceability?
Metrological traceability connects a measurement result to an appropriate reference through a documented, unbroken chain of calibrations, with each step contributing to measurement uncertainty.
In simplified form:
Laboratory instrument → Reference standard → Higher-level standard → National/international reference
Why Is Measurement Uncertainty Important?
No measurement is perfectly exact.
A calibration result might therefore be reported as:
100.02 mL ± 0.03 mL
The uncertainty statement and coverage information given in the certificate are necessary to interpret such a result correctly.
How Often Should Equipment Be Calibrated?
There is no universal calibration interval suitable for every instrument.
The interval should consider:
- Frequency of use
- Equipment stability
- Previous calibration history
- Manufacturer recommendations
- Environmental conditions
- Measurement criticality
- Regulatory requirements
- Risk assessment
Calibration vs Verification
These terms are not identical.
Calibration establishes the relationship between measured indications and reference values.
Verification determines whether specified requirements have been fulfilled.
Conclusion
A calibration certificate provides documented information about measurement results, uncertainty and metrological traceability.
However, not every piece of laboratory equipment requires an individual calibration certificate.
The requirement should be determined according to:
intended use + required accuracy + measurement risk + applicable standards + quality system.
