Glossary of Calibration Terms
Learn the meaning behind common calibration terms.
A
Accreditation
Laboratory accreditation is the formal recognition by an accreditation body that a calibration or testing laboratory is able to competently perform the calibrations or tests listed in the accreditation scope document. Accreditation includes evaluation of both the quality management system and the competence to perform the measurements listed in the scope.
Accreditation Body
An accreditation body is an organization that conducts laboratory accreditation evaluations in conformance to ISO Guide 58.
As Found Data
As found data is the state of the equipment before any calibrations, adjustments or repairs occur.
As Left Data
As left data represents equipment performance and accuracy after any necessary repairs, adjustments, and other calibration steps have occurred.
C
Calibration
Calibration is the process of comparing a device's measurements against an established standard to ensure accuracy, reliability, and safety. It involves testing and adjusting instruments to match known, traceable reference values, reducing measurement errors
Calibration Seal
A calibration seal is a device, placard, or label that, when removed or tampered with, and by virtue of its design and material, clearly indicates tampering. The purpose of a calibration seal is to ensure the integrity of the calibration.
D
Departure Value
In calibration, the departure value refers to the quantified bias, error, or systematic deviation of a measuring instrument’s reading from the true value of a reference standard. It represents the residual inaccuracy after any adjustments have been made.
Drift
Drift is the gradual, often unintentional shift in a measuring instrument's readings over time, causing it to diverge from its previously calibrated standard. It represents a slow change in performance due to factors like aging, wear, or environmental changes, leading to inaccuracies and potential quality issues.
I
ISO
The International Organization for Standardization (ISO) is an independent, non-governmental international organization that develops and publishes voluntary, consensus-based standards for products, services, and systems to ensure quality, safety, and efficiency.
L
Level of Confidence
Level of confidence in calibration is a statistical measure indicating the probability that a measurement result falls within a defined uncertainty interval. It validates that a device's reported accuracy is trustworthy, ensuring that if measurements are repeated, a specified percentage will fall within the expected range.
M
Measurement Standards
Measurement standards are highly accurate physical objects, instruments, or reference materials used as benchmarks to verify, adjust, and ensure the accuracy of other measuring devices.
Measurement Uncertainty
Measurement uncertainty is the quantified doubt about a measurement's reliability, representing the range where the true value likely lies. It is affected by factors like instrument limits, environmental changes, and operator skill, and is crucial for assessing measurement quality by stating the confidence level.
Metrology
Metrology is the scientific study of measurement, encompassing the theory, practice, and application of measurements to ensure accuracy, consistency, and traceability by establishing standards, developing calibration methods, and defining units of measure.
O
Offset
Offset in calibration is the constant error or shift in a sensor’s output reading compared to the true value, representing the difference between the expected and actual measurement when the input is zero or a known baseline. It is often corrected through single-point calibration, by adding or subtracting this difference to align the device with the actual reading.
P
Precision
Precision in calibration refers to the repeatability, consistency, and reproducibility of measurements taken by an instrument under identical conditions. It measures how closely repeated readings agree with each other, rather than how close they are to a true value. High precision means low variability between successive measurements.
W
Work Instruction
A calibration work instruction is a detailed, step-by-step document specifying exactly how to calibrate a specific piece of equipment. It provides precise technical steps—such as required standards, environmental conditions, and acceptance criteria—to ensure consistency, accuracy, and compliance with quality standards (like ISO 9001).