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LIQUID IN GLASS

THERMOMETER

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LIQUID IN GLASS THERMOMETER

a thermometer in which thethermally sensitive element is a

liquid contained in a graduatedglass envelope. Most common and

well known thermometer 

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LIQUID IN GLASS THERMOMETER

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The liquid in glass thermometer are

commonly manufactured in two types

•Total Immersion

•Partial Immersion

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Partial Immersion

Total Immersion

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Expansion Chamber

Capillary Tube

Scale

Stem

Column of Mercury

Constriction

Mercury Bulb

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Expansion Chamber

space that is taken up by the gas inthe capillary bore; it is pushedback as the mercury rises into it.

Parts

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Capillary Tube

space that is taken up by the gas inthe capillary bore; it is pushedback as the mercury rises into it.

Parts

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Column of mercury

quantity of mercury that is contained in thecapillary bore; its height varies with thetemperature.

Parts

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narrowing that prevents the mercury fromspontaneously dropping into the bulb asthe temperature lowers (the thermometermust be shaken to make it go down).

Constriction

Parts

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Mercury Bulb

glass reservoir containing mercury (a

liquid metal) that expands and rises inthe capillary tube as the temperaturerises.

Parts

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Stem

Glass tube containing the capillary bore.

Parts

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Most common type of Liquid inglass thermometer

Mercury

Alcohol

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Mercury in thermometer

It has a boiling point of 674°F (356.7°C) anda melting point of -38°F (-38.89°C). Mercuryis stable (it does not react) in air and water,does not expand upon solidification andtherefore will not break the glass tube of

the thermometer. 

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Alcohol in glass thermometer

spirit thermometer is an alternative to

the mercury in glass thermometer andfunctions in a similar way. But unlikemercury-in-glass thermometer, thecontents of an alcohol thermometer areless toxic and will evaporate away fairlyquickly.

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Mercury Vs Alcohol

Advantages Disadvantages

Mercury Mercury thermometers

are inexpensive, durableand accurate.

they present many safety and

environmental hazards

Alcohol also inexpensive anddurable.

not as accurate as mercurythermometers because of the

alcohol’s susceptibility toevaporation,

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Useable Temperature Range

Working Liquid Temperature rangeMercury -38 to 650

Alcohol -110 to 100

Toluene -90 to 100

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The Liquid Glass Thermometer

Advantages Disadvantages

No power source required Limited to applications

Repeatable Have a limited useable temperaturerange

Easy to use and cheap Cannot be digitized or automated

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