2. Measurement Process Characterization
2.3. Calibration
2.3.1. Issues in calibration

2.3.1.1.

Reference base

Ultimate authority

The most critical element of any measurement process is the relationship between a single measurement and the reference base for the unit of measurement. The reference base is the ultimate source of authority for the measurement unit.

Base and derived units of measurement

The base units of measurement in the Le Systeme International d'Unites (SI) are (Taylor):

• kilogram - mass
• meter - length
• second - time
• ampere - electric current
• kelvin - thermodynamic temperature
• mole - amount of substance
• candela - luminous intensity

These units are maintained by the Bureau International des Poids et Mesures in Paris. Local reference bases for these units and SI derived units such as:

• pascal - pressure
• newton - force
• hertz - frequency
• ohm - resistance
• degrees Celsius - Celsius temperature, etc.

are maintained by national and regional standards laboratories.

Other sources

Consensus values from interlaboratory tests or instrumentation/standards as maintained in specific environments may serve as reference bases for other units of measurement.