Measurement / 31
are moving. Temperature is measured in degrees on the Fahrenheit, Celsius and Kelvin
Thermometric Property : It is the measurable property that changes with respect to
Example : In Mercury thermometer, in this thermometer the thermometric property is
length (Expansion or contraction). With rise in temperature the mercury level rises in the
glass, i.e. change in length.
Measurement of Temperature : The temperature measurement means measurement
of any one of thermometric property of the sensing device. The thermometric property may
be pressure, volume, resistance, length, brightness, etc.
Following are the temperature measurement devices having different thermometric
Constant volume gas thermometer
Constant pressure gas thermometer
Electrical resistance thermometer
Pressure : It is the force exerted by the fluid on unit area perpendicular to it.
It is usually expressed in Pascal (Pa = N/m2)
Measurement of pressure : Many techniques have been developed for the measurement
of pressure. Instruments used to measure pressure are called pressure gauges. Pressure is
also measured by instruments like Piezometer, Manometers, Bourdon Pressure gauge,
Pressure transducers etc.
1. Manometers : Manometers are the devices which are used for measuring the pressure
at a point in a fluid by balancing the column of liquid by another column of liquid. They are
classified as :
(i) Simple Manometer :
U-tube manometer (c)
Single column manometer
Liquid or water