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Measurement of Temperature

There are three scales of measurements - the Fahrenheit, the Centigrade or Celsius, and the Kelvin. The most common scales by which we measure are the Fahrenheit and the Celsius scales. To get a standard scale of graduation or marking on the thermometer, there should be two fixed points - the lower and the upper.

The Fahrenheit scale was developed by Gabriel Fahrenheit and was widely used. It had three main reference points - a boiling point, a freezing point and the zero point. Fahrenheit decided to invent a zero point, which would be low enough so that minus values would not normally be required to measure temperatures during the winter.

Anders Celsius developed the centigrade scale (later known as the Celsius scale). It used the freezing point of water as its zero point, and used 100 degrees between the freezing and boiling points. The melting point of pure, dry ice is the lower fixed point and the boiling point of water is the upper fixed point in the centigrade scale.

Lord Kelvin of England developed the Kelvin scale. He moved the zero point down to the absolute zero (the temperature at which a substance loses all its heat). He retained the 100 degrees between the freezing and the boiling points.

Table - Thermometric Scales


Type of Thermometer

Lower fixe point

Upper fixed point

No. of divisions



0° C

100° C




32° F

212° F




273° C

373° C


The space between the lower and upper fixed points are divided according to the type of thermometer constructed.

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