Measurement of temperature.

In topics like metallurgy and heat treatment processes, we often come across high temperature like upto 800 degree centigrade and above.

Now what i would like to know is how these temperatures are measured, since the regular laboratory thermometer is only graduated upto 100 degree centigrade. if this thermometer was subjected to a temperature more than its upper limit then what would happen ? would it explode ?

and another thing : what is the big difference between a laboratory thermometer and a clinical thermometer? the latter has its lower limit as 105 degree centigrade. can these two be used as substitutes for each other ?

Replies

  • ISHAN TOPRE
    ISHAN TOPRE
    Measurement of temperatures is governed by Zeroth law of thermodynamics.

    Whether it will explode or not depends upon the properties of glass in which mercury is contained. The glass has high melting point but as it is brittle, it will crack for sure. The mercury will be spread in droplets on the floor.

    For measuring high temperatures we have optical Pyrometers, They measure temperatures by the color of metals at elevated temperatures. For accurate measurement in laboratories, Platinum probe thermometers. Depending upon the the range of temperatures and accuracy desired we have different temperature measuring instruments.

    I recommend you read "Thermodynamics: An Engineering Approach" by Yunus Cengel and Michael Boles.

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