Modes of measurements

1. Primary measurement 
2. Secondary measurement
3. Tertiary measurement 

1. Primary measurement: 

•  In this case sought value of parameter is determined by comparing it directly withing reference standard 
• There is no conversation of measurand in terms of length
  1. measurement of time by counting the number of stroke of the clock.
  2. Matching of 2 length when determining the lenght of an object with a ruler
  3.   Matching of 2 colors when judging the temperature of a red hot steel.
     

2.Secondary measurement:

The indirect measurement ,these involving 1 translation. 

•  temperature measurement by  mercury in glass(Thermometers)
• pressure measurement by manometer.
  
  

3.Tertiary measurement:

The indirect measurement ,these are involving 2 translations

• The measurement of temperature of an object by thermocouple.