17-08-2013, 04:49 PM
Pyrometers
To measure temperature of a very hot body
Where thermometers cannot brought into contact or
Where hot bodies are moving
Measurements done by measuring energy radiated by a hot body or by comparison of colour
Lens – for focusing targets
Uses selective materials to prevents absorption by them
Thallium iodide – more suitable for high temp with shorter emission
fused silica -High temp with shorter wavelength – b/w 250 to 1900 C
Pyrex
Advantages
Abitity to measure high temp
No need for contact
Fast response speed
High o/p
Moderate cost
disadvantages
Non linear scale
Emmisivity of target affect measurement
Errors due to interleaving media
Optical pyrometer- working
disappearing filament type
Radiation received by objective lens- focus on filament- viewed through a microscope system- filament appears in background.
red cadmium filters makes the radiation appear momchromatic
To measure temperature of a very hot body
Where thermometers cannot brought into contact or
Where hot bodies are moving
Measurements done by measuring energy radiated by a hot body or by comparison of colour
Lens – for focusing targets
Uses selective materials to prevents absorption by them
Thallium iodide – more suitable for high temp with shorter emission
fused silica -High temp with shorter wavelength – b/w 250 to 1900 C
Pyrex
Advantages
Abitity to measure high temp
No need for contact
Fast response speed
High o/p
Moderate cost
disadvantages
Non linear scale
Emmisivity of target affect measurement
Errors due to interleaving media
Optical pyrometer- working
disappearing filament type
Radiation received by objective lens- focus on filament- viewed through a microscope system- filament appears in background.
red cadmium filters makes the radiation appear momchromatic