Calibration
Calibration involves determining the metrological characteristics of an instrument. This is achieved by means of a direct comparison against standards. A calibration certificate is issued and (mostly) a sticker attached. Based on this information a user can decide whether the instrument is fit for the application in question.
Some more information can be obtained by clicking any of the items below:

• measurement standard / etalon
• international (measurement) standard
• primary standard
• reference standard
• working standard
• traceability
• calibration
• reference material
• certified reference material

(measurement) standard / etalon
Material measure, measuring instrument, reference material or measuring system intended to define, realize, conserve or reproduce a unit or one or more values of a quantity to serve as a reference.

Examples
a) 1 kg mass standard
b) 100 Ω standard resistor
c) standard ammeter
d) cesium frequency standard

international (measurement) standard
Standard recognized by an international agreement to serve internationally as the basis for assigning values to other standards of the quantity concerned.

primary standard
Standard that is designated or widely acknowledged as having the highest metrological qualities and whose value is accepted without reference to other standards of the same quantity.

reference standard
Standard, generally having the highest metrological quality at a given location or in a given organization, from which measurements made there are derived.

working standard
Standard that is used routinely to calibrate or check material measures, measuring instruments or reference materials.

A working standard is usually calibrated against a reference standard.

traceability
Property of the result of a measurement or the value of a standard whereby it can be related to stated references, usually national or international standards, through an unbroken chain of comparisons all having stated uncertainties.

calibration
Set of operations that establish, under specified conditions, the relationship between values of quantities indicated by a measuring instrument or measuring system, or values represented by a material measure or a reference material, and the corresponding values realized by standards.

Notes
1. The result of a calibration permits either the assignment of values of measurands to the indications or the determination of corrections with respect to indications
2. A calibration may also determine other metrological properties such as the effect of influence quantities
3. The result of a calibration may be recorded in a document, sometimes called a calibration certificate or a calibration report

reference material (RM)
Material or substance one or more of whose property values are sufficiently homogeneous and well established to be used for the calibration of an apparatus, the assessment of a measurement method, or for assigning values to materials.

Note
A reference material may be in the form of a pure or mixed gas, liquid or solid. Examples are water for the calibration of viscometers, sapphire as a heat-capacity calibrant in calorimetry, and solutions used for calibration in chemical analyses.

certified reference material (CRM)
Reference material, accompanied by a certificate, one or more of whose property values are certified by a procedure which establishes traceability to an accurate realization of the unit in which the property values are expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence.