TITLE.PM5

30 ENGINEERING THERMODYNAMICS

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M-therm/th2-1.pm5

Types of Liquid

in Bimetal-

Radia-

Optical

instru-

glass

lic ther-

Pressure thermometers

Thermocouples

Resistance thermometers

tion

pyro-

ments

ther-

mometer

pyro-

meters

mometer

meters

Mercury

Vapour

Liquid

Gas

Iron-

Copper-

Chromel-

Platinum

Copper

Nickel

Plati-

• 
  


• 
  

pressure

filled

filled

Constan- Constan-

Alumel Pla

tinum-

num

tan

tan

Rhodium

Low

About

tempera-

• 39°C


• 75°C


• 250°C


• 87°C


• 269°C – 196°C – 250°C

–184°C

0°C

• 140°C – 184°C –

184°C

room

760°C

ture limit

temp.

High

As high

As high

tempera-

600°C

540°C

316°C

650°C

540°C

760°C

350°C

1260°C

1540°C

120°C

316°C

760°C

as

as

ture limit

desired

desired

Remark

Low

Easier to Normal-

To

be

Requires

Widely Constan-

Chromel

Expen-

Very sensitive. Suitable

price ;

read

ly

scale

compen-

large

used in

tan is

is

20% ;

sive

for narrow range instru-

Fairly

than Liq.

non-

sated for

bulb ;

Industry.

60% Cu Cr 80% ;

ments

—

—

accurate ;

uid-in-

linear

variation

Linear

40% Ni

Ni-

Easily

glass

in

ambi-

scale

Alumel

broken

ther-

ent temp-

is 2% Al,

mometers

eratures

98% Ni,

Table 2.2. Summary of temperature range of different instruments