1.3 Standards of Measurements

Definition:
Defined by international agreement and they represent certain units of measurement to the closest possible accuracy that production and measurement technology allow. These standards are periodically evaluated and checked by absolute measurements in terms of fundamental units. These standards are maintained at the International Bureau of Weight and Measures in Paris.

Function:
May be used for comparisons with primary standards.

Definition:
The primary purpose of primary standards is to verify and calibrate secondary standards. National standards laboratories in many countries maintain these standards. At each of the national laboratories these are calibrated individually using absolute measurements. The results of such measurements are compared against each other, leading to a world average figure for the primary standards. Primary standard are not available for used outside the national laboratories.

Function:
Verification and calibration of secondary standards.

Definition:
These standards are the basic reference standards used by measurement and calibration laboratories in the industry to which they belong. Each laboratory periodically sends its secondary standards to the primary standards in national standard laboratories. After calibrate the secondary standards are returned to the industrial laboratory with certification of measuring accuracy in term of a primary standard.

Function :
Issues a certificate of measuring accuracy in term of a primary standard.

Definition:
Principle tools of a measurements laboratory. High accuracy devices that commercially available and dully check.

Function:
Check and calibrate the instruments use in the laboratory.