Calibration

Calibration compares an instrument’s readings with known standards to determine their relationship and, when needed, adjust the instrument’s response.

Measurement standard: A reference that realizes or defines a quantity used to compare measurements. A standard supplies the known value against which an instrument’s reading is assessed.
Measurement: The process of experimentally obtaining one or more values that can reasonably be attributed to a quantity. Calibration is part of measurement practice, but does not itself guarantee every measurement is correct.
Pressure gauge: An instrument that measures the pressure of a fluid relative to a reference pressure. Pressure gauges are calibrated against known pressures to establish their indicated values.
Verification: Confirmation, supported by objective evidence, that specified requirements have been fulfilled. Verification checks whether requirements are met; calibration characterizes readings against standards.
Calibration curve: A relationship between known reference values and an instrument’s corresponding responses. A curve expresses how readings map to the quantity being measured across a range.
Accuracy and precision: Accuracy concerns closeness to a true or reference value; precision concerns agreement among repeated results. Calibration can improve accuracy without necessarily changing the precision of repeated readings.
Thermometer: An instrument that measures temperature through a physical property that varies with temperature. Thermometers are compared with temperature references across their working range.
Validation: Confirmation that a method or system is suitable for its intended use. Validation addresses fitness for purpose rather than an instrument’s relationship to standards.
Measurement uncertainty: A quantified description of the doubt associated with a measurement result. Calibration results have uncertainty that limits how precisely an instrument can be characterized.
Systematic error: A consistent measurement error that shifts results in a predictable direction or pattern. Calibration can reveal and correct systematic response errors.

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