13 Field Instrumentation GEN Rev)
LIQUID IN GLASS THERMOMETERS Its operation is based on the principle that liquids expand as temperature increases. It consists of a small bore glass tube with a thin wall glass tube at its lower end. Liquid filled is usually mercury or an organic compound.
FILLED THERMAL SYSTEMS The basic components of a
filled system thermometer are o Thermometer bulb o
Capillary tube o Bourdon tube The entire system is filled with filling fluid. A change in temperature causes the
fluid to expand or contract, in turn causing the bourdon tube to move.
Liquid filled system: A bulb is inserted into the substance to be measured. Filling liquid inside the bulb commonly toluene or xylene) is heated or cooled until the temperature of the filling liquid matches the temperature of the measured substance. Mercury is also used as filling fluid due to rapid response to temperature changes.
A LIQUID FILLED THERMOMETER
AND ITS DIFFERENT PARTS 14 Field Instrumentation GEN Rev)
Gas filled systems: It operates on the principle that the pressure of a confined gas varies directly with its absolute temperature.
P=kT, where k=constant, and T=absolute temperature. Nitrogen gas is normally used as filled gas.
Share with your friends: 
