referansetilstand

Referansetilstand, or reference state, is a defined and stable set of conditions used as a baseline for measurement, calculation, and comparison. It specifies key parameters such as temperature, pressure, composition, and phase, so that changes observed in a system can be meaningfully quantified. The reference state serves as the zero or starting point from which differences are measured, for example in thermodynamics, chemistry, materials science, and instrumentation.

In practice, referansetilstand is chosen to be reproducible and well documented. Common examples include standard states used in chemistry, such as a specified temperature and pressure (often 25°C and 1 bar) for standard enthalpy and free-energy data. In experimental work or sensor calibration, the reference state corresponds to the condition at which readings are defined as baseline, with subsequent results expressed as changes relative to this baseline (for instance, ΔH, ΔG, or ΔT).

The concept is not tied to a single field; its precise definition varies by domain. What remains constant is the role of the reference state as a stable, defined point against which observations are compared. Clear specification of the referansetilstand is essential for reproducibility, interpretation of results, and alignment with standards and regulatory requirements.

See also: reference state in physics and chemistry, standard state, calibration.