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- Kimball Electronic Laboratory, INC.
Calibration is the process of comparing a measuring instrument or piece of test equipment against a known reference standard to determine how accurately it is performing. It helps organizations maintain reliable measurements, identify equipment that has drifted out of tolerance, and support consistent quality and compliance.
Organizations rely on measurement equipment to make decisions about products, processes, maintenance, inspections, and safety. If the equipment producing those measurements is inaccurate, those decisions may also be unreliable.
Regular calibration helps organizations:
Although the exact procedure depends on the type of equipment being calibrated, the basic process generally follows the same principle.
1. The instrument is inspected.
The equipment is reviewed for its condition, identification, specifications, and calibration requirements.
2. A suitable reference standard is selected.
The technician uses calibration standards appropriate for the instrument and measurement being tested.
3. Measurements are compared.
The instrument under test is compared with the reference standard at specified measurement points.
4. Results are evaluated.
The measured values are evaluated against the applicable specifications or tolerances.
5. Results are documented.
The calibration results are recorded and, when applicable, provided on a calibration certificate.
This process creates documented evidence of how the instrument performed at the time of calibration.
Calibration, verification, and adjustment are related concepts, but they do not mean exactly the same thing.
Calibration compares an instrument’s measurement performance against a reference standard and documents the results.
Verification confirms whether equipment satisfies specified requirements or tolerances.
Adjustment involves making a physical or electronic change to the instrument to improve its measurement performance.
For example, a technician may calibrate a pressure gauge and discover that its readings are outside the required tolerance. An adjustment may then be performed, followed by another calibration to determine its performance after the adjustment.
Understanding these differences is important when establishing equipment maintenance and calibration procedures.
There is no single calibration interval that applies to every instrument.
Some equipment may require calibration every six months, while other equipment may be calibrated annually or according to another established interval.
Factors that can influence calibration frequency include:
Measurement traceability provides a documented connection between a measurement result and recognized reference standards through an unbroken chain of calibrations.
Each step in that chain contributes to the overall measurement uncertainty.
Traceability is important because it allows measurement results produced by different laboratories, facilities, and organizations to be related to recognized measurement references.
For organizations that depend on accurate measurements, traceability provides greater confidence that measurement results have a documented and technically supported basis.
ISO/IEC 17025 is the international standard used to assess the competence of testing and calibration laboratories. Accreditation provides additional assurance that a laboratory has demonstrated competence for specific calibration capabilities.
Because accreditation is scope-specific, customers should verify that the calibration capability they require is included within the laboratory’s accredited scope.
After calibration, the laboratory typically provides documentation identifying the equipment and the work performed.
Depending on the calibration and customer requirements, a certificate may include information such as:
Calibration ultimately provides confidence in measurement.
Organizations use measurement equipment every day to inspect products, maintain aircraft, verify processes, manufacture components, troubleshoot systems, and make quality decisions. Those activities depend on the instruments producing sufficiently reliable results.
A properly managed calibration program helps ensure measurement equipment remains suitable for its intended use while providing the documentation and traceability necessary to support quality requirements.
