Calibrating

Calibrating, in measurement and instrumentation, is the process of configuring an instrument, sensor, or system so that its output corresponds to a defined standard. The aim is to establish the relationship between the instrument's readings and a reference quantity, ensuring accuracy, traceability, and comparability over time and across devices.

Calibration typically begins with defining the measurement range and performance criteria, selecting an appropriate reference standard, and performing a series of measurements. The observed values are compared with the known values of the standard; the resulting difference, or error, is analyzed to determine a correction factor or adjustment. If the instrument is adjustable, it may be set to minimize discrepancy; if not, a correction or calibration constant is stored in software or in a certificate. Documentation, including the calibration certificate and any uncertainty estimates, records the results and establishes the next due date for recalibration.

Key concepts include traceability to national or international standards, measurement uncertainty, and calibration curves that describe how output varies with input. Calibration is distinct from verification (checking that an instrument remains within tolerance without adjusting it) and from validation (assessing whether a system performs as intended in its real use).

Standards and practice are guided by laboratory accreditation and quality systems, such as ISO/IEC 17025 and related standards. Calibration is common in scientific laboratories, manufacturing, healthcare, environmental monitoring, and consumer electronics, and it can involve diverse instruments from thermometers and balances to sensors and complex instruments.