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Melvin Soriano (melvin)
New member
Username: melvin

Post Number: 3
Registered: 2-2013
Posted on Friday, March 01, 2013 - 1:48 am:   

Thank you Howard. I will surely browse on that particular article as you have recommended.
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Howard Mark (hlmark)
Senior Member
Username: hlmark

Post Number: 524
Registered: 9-2001
Posted on Thursday, February 28, 2013 - 9:21 am:   

Arguably the most famous (or infamous) article published in NIR News (NIR News, 3(1), p.8-9 (1992)) is one Tony himself wrote describing the effect of varying temperature and humidity in the laboratory due to the cycling of the air contiioner. The title might be a little misleading when you're looking for it, but is certainly pertinent to the current discussion: "Water Vapor Noise in NIR Spectra".

That was over 20 years ago, and hopefully air conditioners and their ability to maintain constant ambient conditions have improved since then, but never discount the possiblity of trouble from that source.

\o/
/_\
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Melvin Soriano (melvin)
New member
Username: melvin

Post Number: 2
Registered: 2-2013
Posted on Wednesday, February 27, 2013 - 8:02 pm:   

Hello Pierre and Tony, thank you very much for your inputs. To answer Tony's questions, the limit of 0.012 noise RMS is set by our company's NIR BMP on instrument performance test. We do the performance test weekly or as needed using 10 cycles. By the way, I'm from the Philippines which is a tropical country. We have a separate room for our NIR instrument where we manage T and H using A/C units and dehumidifier. I would like to gather as much information I can get in ways to improve our noise RMS because right now, the usual value we are getting is only the manufacturer's limit. Unfortunately, some of our location in the SEA region is meeting the BMP requirement of 0.012. As of now, we have only explore keeping the T and H reading as stable as it can be. I would like to know what other areas do you suggest I looked at which have direct impact on the noise RMS (age of instrument or part of the instrument, location of NIR with respect to A/C and dehumidifier, light sources). I am also looking at challenges brought about by lab design thus I included a screen capture of our lab showing the position of our NIR room with respect to other areas of the lab.
application/octet-streamlab diagram showing NIR room
Lab diagram.docx (84.0 k)
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Tony Davies (td)
Moderator
Username: td

Post Number: 296
Registered: 1-2001
Posted on Wednesday, February 27, 2013 - 4:54 am:   

Hello Melvin,

Welcome to the group.

Where does this figure of 0.012 in your BMP come from? Does it detail how the test should be done?

The noise levels on NIR instruments are very low compared to most analytical instruments. When I first became involved with NIR in the 1980's no one would believe that you could get noise levels below 100 micro absorbence units (or why you would want to!).

My guess is that there is a confusion about the units.

If you are better than the manufacturer's specification there is not much you can do without building an improved version of the instrument (like Karl Norris did in the 1960's). But believe us, you do not need to.

Best wishes,

Tony

Best wishes,
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Pierre Dardenne (dardenne)
Senior Member
Username: dardenne

Post Number: 78
Registered: 3-2002
Posted on Wednesday, February 27, 2013 - 3:57 am:   

Hi,

You can not reach 0.012 with a 6500 unless you multiply by 9 the number of subscans.
The BMP must be changed according the performance of the instrument. The instant noise of these instruments is very good and this is not the most important diagnostic. When you scan twice the same powder with refilling the cup, an average RMS is 2000 �log; it means the instrument repeatability of 30 �log does not influenced at all the prediction repeatability. A diagnostic which is more important is the checkcell overtime; seasonal variations are observed depending on the changes of the environment (T� & hygrometry); this is the main source of variation.

Pierre
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Melvin Soriano (melvin)
New member
Username: melvin

Post Number: 1
Registered: 2-2013
Posted on Tuesday, February 26, 2013 - 8:01 pm:   

Hi, I am quite new in this forum so I hope I have placed this question in the right category or section. I would like to ask for advice or opinion on noise test RMS. Our BMP requires a RMS value of not greater than 0.012. By the way we are using FOSS NIRS5000, the manufacturer's RMS limit is around 0.02-0.03. Can anybody share their expertise on managing this RMS requirement like what areas or factors must be controlled, etc. Hope to hear from all of you soon. Thank you in advance.

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