where expertise comes together - since 1996

Web's Largest Portal of Nondestructive Testing (NDT)
Open Access Database (Conference Proceedings, Articles, News), Exhibition, Forum, Network

All Forum Boards
Technical Discussions >
IR Thermography
Career Discussions
Job Offers
Job Seeks
Classified Ads
About NDT.net
Articles & News

747 views
09:19 Nov-27-2002

zaki

,
Joined

IR Thermography


Just for curiosity..

In Thermography method, measurement appear in Temperature (oC), but theoritically the measurement is performed in term od total receiving radiation power (W). Is there any relationship between temperature vs. radiation..



 
09:55 Nov-27-2002

Alberto Monici

Engineering, Leak Detection Service - Thermography Service -
ETS Sistemi Industriali,
Italy,
Joined Aug 2002
17
Re: IR Thermography Dear Mr.Zaki
For a black-body the relationship is that gived by Plank's law, in wich:
W= (2*pi*h*c^2)/((lambda^5)(e^(hc/lambdakT)-1))
in which W is the spectral emissivity [Watt/m^2*meter] and T is the black-body temperature in Kelvin.
The intergal of the Plack formula in all the lambda possible give the Total Energy Emission (Stefan-Boltzmann law):
Wt=k*T^4
where k is the Stefan-Boltzmann constant.
For a grey-Body (like that normally measured in nature), the emissivity of the body, its spectral transmittance and the spectral absorbing coefficient give a total emittance below then a black-body. So the formula is: Wt=E*k*T^4, where E is the ratio between emittance of grey and black bodies.
I Hope to be exhaustive for your couriosity. Don't exitate to contatct me for any other question.


:
: Just for curiosity..
.
: In Thermography method, measurement appear in Temperature (oC), but theoritically the measurement is performed in term od total receiving radiation power (W). Is there any relationship between temperature vs. radiation..
.



 
01:33 Dec-02-2002

Robert Paynter

R & D, Research Assistant
U of Oxford,
United Kingdom,
Joined Jun 2001
14
Re: IR Thermography Alberto Monici wrote:
: Dear Mr.Zaki
: For a black-body the relationship is that gived by Plank's law ...

:: Just for curiosity..
:
: In Thermography method, measurement appear in Temperature (oC), but theoritically the measurement is performed in term od total receiving radiation power (W). Is there any relationship between temperature vs. radiation..
: .
.
Alberto Monici gave the total, but most sensors have a limited band of detection and you need to allow for that. CMT (Cadmium/Mercury/Telluride) is the favourite at typical ambient temperatures because it's response ends up being almost linear in this range. InSb (Indium Antimonide) can do these low temperatures but is much better (more linear) at higher (600K +).
They are well behaved responses so will be calibrate within the camera.

As a user you need to take care that the emission of your observed surfaces is taken into account - some are unexpectedly good with IR eg. white snow.

Robert


 


© NDT.net - The Web's Largest Portal of Nondestructive Testing (NDT) ISSN 1435-4934

Open Access Database, |Conference Proceedings| |Articles| |News| |Exhibition| |Forum| |Professional Network|