Viitemittari

Viitemittari, literally "reference meter" in Finnish, denotes a class of measurement devices or setups that provide a stable, known reference value for calibration and verification of other instruments. It is not a single standardized instrument but a category used in metrology to ensure traceability and accuracy in measurement chains.

Principle and design: A viitemittari typically offers a highly stable output, with well-characterized drift, noise, and environmental sensitivity. Outputs can be electrical (voltage, current), optical (power, wavelength), or other physical quantities, depending on the measurement field. Its value is maintained through calibration against recognized standards and is supported by temperature control, shielding, and regular drift monitoring. All output values are documented with an uncertainty budget and a calibration certificate traceable to SI units.

Applications: Used in calibration laboratories, manufacturing quality control, and field verification routines, viitemittari devices serve as reference points to test the accuracy of portable instruments, monitors, and data acquisition systems. They are common in electrical metrology, optics, acoustics, and dimensional metrology, where stable references are essential.

Standards and traceability: A viitemittari is designed to be traceable to international standards via an established calibration chain. Calibration intervals, environmental specifications, and uncertainty analyses are governed by quality systems such as ISO/IEC 17025.

Limitations: While providing a stable reference, a viitemittari is subject to drift, environmental sensitivity, and maintenance requirements. It does not replace regular instrument calibration but supports it.

See also: Metrology, Calibration, Reference standard, Traceability, Uncertainty.