# Metrology

#### I.1. Basic concepts of metrology

*What was the prerequisite for the formation of the Institute of Metrology? From which base units do all the others count? You will learn about this in the article "Introduction to Metrology"*

#### I.2. Measurements

*Could you imagine that in order to carry out a laser measurement, it is necessary to increase the pressure in the room? So, all the dust will settle and the air will be cleaner. About this and other factors in the article "Measurements"*

#### I.3. Uncertainty

*20±5 - for some it is from 15 to 25, and for others it is the uncertainty of measurement. How to correctly record the measurement result and enter all possible errors, find out in the article "Uncertainty"*

#### I.4. Total uncertainty

*If several factors affect the measurement, then it is necessary to find the entire range of the spread to search for the worst of the options, and if the factors depend on each other, enter a correlation coefficient.*

#### I.5. Example of uncertainty

*The Chamber of Weights and Measures provides documents describing the method of calculating uncertainty. The document is an ISO 98-3 standard, which provides several examples of calculation, in the article we have prepared one of the examples.*

#### I.6. Effective degrees of freedom

*Welch-Satterthwaite introduced a formula for calculating degrees of freedom when several factors are used, for example, to calculate the total uncertainty*