| Author | Message | |||
     Art Springsteen (artspring) Senior Member Username: artspring Post Number: 47 Registered: 2-2003 |
Hello Gabriela, We do these measurements and calculations all the time using UV Winlab, which is probably what you are also using on your PE950. We've been running this and earlier iterations of the PE software for over 20 years. There are a couple ways of doing the calculation: 1) run baseline with white standard, then run your sample. Multiply (reflectance of sample x reflectance factor of reference). Let's call this product RS. Take this result (RS) and take log of 1/RS. This gives you absorbance. 2) As above, then use the TAAT function in the software. This will again give you (nominally) the absorbance. Note that when I say 'reflectance', it is just that, not %reflectance, so if you have %reflectance, you need to divide that number by 100. Hope that helps! Art S. | |||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 516 Registered: 9-2001 |
Gabriela - best thing to do is to contact the manufacturer of the Lambda 950 and ask their Applications scientists how their calculation is performed. Then you can compare that with your own calculation. One pssibility is that in one case the entire spectrum is expanded, so that the range 17.6% to 54% is expanded to fill the range 0-100% while in the other case the range 0% to 54% is expanded to be 0-100%. But only the manufacturer knows for sure \o/ /_\ | |||
| gabriela dasko (gaba_p) New member Username: gaba_p Post Number: 1 Registered: 12-2012 |
Please can you help me. I run spectrum for metal panel decorated with grey ink. I register Reflectance between 400nm and 850nm using lambda 950. Max reflectance is 54 % for 850nm and min 17.6% at 400nm raw spectrum. I need to normalize spectrum to 100% R. If I use ready Lambda 950 equation , A= log(1/R) or excel as 54/100 =factor 1.8 *54 = 100% R (traditional way) I have different results. Raw spectrum R=17.61 % at 400, after Lambda normalization A=log (1/R) I have R=8.11 % at 400, excel : R=32.811% , both based on raw spectrum. Why Lambda normalization gave me lower value for Reflectance? what data is taking for equation? I can send full spread sheet in excel R to nm . Please help!
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