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The next quality standard in the hierarchy is known as a secondary standard. Secondary standards are calibrated with reference to a primary standard. [2] The third level of standard, a standard which is periodically calibrated against a secondary standard, is known as a working standard. [2] Working standards are used for the calibration of ...
A primary standard in metrology is a standard that is sufficiently accurate such that it is not calibrated by or subordinate to other standards. Primary standards are defined via other quantities like length, mass and time. Primary standards are used to calibrate other standards referred to as working standards. [1] [2] See Hierarchy of Standards.
The EPA reviewed this NAAQS in 1985 and 1996, and in both cases concluded that the existing standard was sufficient. The most recent review by the EPA occurred in 2010, resulting in a new 1-hour NO 2 primary standard set at 100 ppb; the annual average of 0.053 ppm remained the same. Also considered was a new 1-hour secondary standard of 100 ppb.
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Secondary instruments must be calibrated against a primary standard. For example: a dial bourdon tube type pressure gauge must be calibrated against a water or mercury U tube to assure good accuracy. Time. The earth moving in its orbit is primary. Clocks must be calibrated against it.
A standard solution created from a secondary standard cannot have its concentration accurately known without stoichiometric analysis against a primary standard. An example of a secondary standard is sodium hydroxide, a hydroscopic compound that is highly reactive with its surroundings. The concentration of a standard solution made with sodium ...
Primary vs. secondary mortgage market. The primary mortgage market is where borrowers get mortgages from lenders. For example, if you go to a local credit union and a couple of banks to get a ...
Secondary reference standards: Reference standards calibrated against and traceable to primary WHO materials and intended for use in routine tests; Reference reagent: a WHO reference standard, the activity of which is defined by WHO in terms of a unit; For chemical substances some pharmacopoeias [10] use the WHO terms [11]