PRINCIPLE:-
The
thermometer is a simple , portable manually operated instrument which may be
used for measurement of a temperature .
TYPES OF THERMOMETER :-
1) Liquid
in glass thermometer .
2) Bimetallic
thermometer .
3) Pressure
thermometer.
a)
Liquid pressure thermometer
b)
Vapor pressure thermometer
LIQUID
IN GLASS THERMOMETER
CONSTRUCTION
& WORKING :-
The liquid in glass
thermometer is one of the most common types of temperature measuring instrument.
It consists of a glass envelope , a
responsive liquid and an indicating scale . The envelope consist a thick walled
glass tube with capillary bore and a spherical or cylindrical bulb filled with
the liquid . The size of capillary is depend on the size of bulb.
It works when changes in temperature
will cause the fluid to expand and rise up in the stem . Since the area of stem
is much less than the bulb , the relatively small changes of fluid volume
results in significant fluid rise in the stem .The length of the movement of free surface of the fluid
column serves by a proper calibration , to indicate temperature of the bulb.
ADVANTAGES:-
Simplicity of use and relatively low
cost .
Easily portable .
Auxiliary power is not required.
No need of additional indicating
instruments.
Good accuracy .
LIMITATIONS:-
1) Cannot
be adopted for automatic recording .
2) Time
lag in measurement.
3) Range is limited up to 600 C.
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