A calibration certificate is a document stating that a device’s calibration is traceable to a standardized reference, such as the National Metrology Institute (NMI) of the country where it was produced. In the context of metrology, the word traceable means that the calibration result for a precision measurement instrument can be traced to a standard reference through an unbroken chain of calibrations, each of which contributes to the measurement uncertainty.
The document itself includes information such as the following:
- Name and details of the device
- Certificate identification code
- The laboratory that conducted the calibration
- Environmental conditions in the location of the calibration
- Results of the calibration
- Evidence of traceability
However, the specific format and details included may vary depending on the type of measuring tool and certificate.
NIST-traceable calibration
In the US, the National Institute of Standards and Technology (NIST) is the gold standard of reference for calibration and measurement. When you purchase a precision measurement device that is NIST-traceable, you have confirmation that it was calibrated using equipment that meets NIST standards to achieve the highest possible accuracy.
Accredited calibration certificate
These are international certificates of calibration from an ISO (International Organization for Standardization)-accredited facility. Specifically, an ISO/IEC 17025 accreditation sets requirements specific to testing and calibration laboratories, which verifies technical competence and the traceability of measurements.
Non-accredited calibration certificate
These types of certificates come from facilities that have not been accredited by ISO. Typically, they are created by the manufacturer and contain calibration details based on the company’s own set of standards.
Conformance certificate
A conformance certificate is not the same as a calibration certificate. These are usually directly from the original equipment manufacturer (OEM), and are used to display the overall quality of a product. They include little, if any, information on calibration measurements.
Calibrating your measurement instruments
When you initially purchase a device with a calibration certificate, it will be traceable to the standard reference used. But with time and use, the traceability – and therefore, overall accuracy – of your device will decrease. This is why regular calibration of your high precision metrology equipment is of the utmost importance. For the most accurate performance, learn calibration methods for each of your precision measurement tools and calibrate them at regular intervals.
FREQUENTLY ASKED QUESTIONS
- What details are included in a calibration certificate?
Most calibration certificates will contain the name and details of the device, a unique identification code for the certificate, information about the facility and environmental conditions where the calibration was performed, the calibration results and evidence of traceability.
- Why should I look for an accredited calibration certificate?
As a customer, you should seek an accredited versus a non-accredited calibration because it confirms that the device’s calibration was performed by an ISO-accredited facility. Non-accredited calibration certificates are usually directly from the manufacturer, with no third party overseeing operations at the facility.
- Why do I need to calibrate my device even if it has a calibration certificate?
A calibration certificate states that the product is traceable to a standard reference. However, all metrology instruments — no matter how accurate when you purchase them — become less traceable over time, particularly with frequent use. To maintain the accuracy of your device and ensure optimal performance, you should make sure you calibrate it at regular intervals.
GLOSSARY TERMS
- National Metrology Institute (NMI)
an institute responsible for setting and maintaining national standards of measurement, such as NIST in the US
- Traceability
the property of a measurement in which the result can be linked to a standard reference (such as NIST) through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty
- ISO
the International Organization for Standardization, an independent, non-governmental international organization that sets and maintains market-relevant international standards