Temperature Measurement

Mitesh kumarRall no-10300513026

Applied Electronics & Instrumentation Engg.Haldia Institute of Technology

Bimetallic Strip

Bimetallic Dial Thermometer

Bimetallic Dial Thermometer working

Helical type

Video on bimetallic property

9. Thermodynamics - Example - Thermal Expansion Bimetal strip.mp4

Filled in system

• Class I – liquid filled• Class II – vapor filled• Class III – gas filled• Class IV/V – mercury filled

Class I – liquid filled

Class II – vapor filled

II A II B

Class II – vapor filled

II C II D

Class III – gas filledClass IV/V – mercury filled

Class V

Thermopile

Thermocouple Sheath

• Thermocouple junctions are prone to contamination by gases,liquids,and other metals.

• The metals contamination alters the thermoelectric behavior of the device such that its characteristic varies from that published in standard table.

Table for sheath metalsmaterial Max operating temp(c)

Mild steel 900 ⁰C

Fused silica 1000 ⁰C

Recrystallised alumina 1850 ⁰C

Magnesia 2400 ⁰C

Thoria 2600 ⁰C

Ice bath tech

Iso-thermal block

• Insert short cu wire b/w both voltmeter terminals and thermocouple leads and place these new junction on an iso-thermal block

• This change eliminates the junctions J3 & J4 because cu is joined to cu at these points

• Place ref. junction not in ice bath but in isothermal block.• From the law of intermediate metals we know that when

junctions in series are at same temperature their makes no change

• Finally J4 and Jref can be replaced by one junction.

Iso-thermal block

Suction Pyrometers