| Author | Message | ||
     udayakumar kanniyappan (udayakumar) New member Username: udayakumar Post Number: 2 Registered: 10-2010 |
Thank you to mr.howard mark and mr.davidd vonn for your prompt reply. | ||
| David von Boisman (david_von_boisman) Advanced Member Username: david_von_boisman Post Number: 22 Registered: 2-2006 |
For that sort of reparation, 600 USD is actually not a lot of money. We're talking about the very heart of the instrument here. Its certainly worth a few bucks extra to have a trained service engineer to repair it. If someone without the proper knowledge tries to fix he might get the motor running, but you�ll probably end up with an instrument that impossible to calibrate or which has its wavelength scale totally off. | ||
| Howard Mark (hlmark) Senior Member Username: hlmark Post Number: 364 Registered: 9-2001 |
Uday - if the motor isn't running, that does not necessarily mean that the motor is broken; motors are usually pretty robust and reliable, and the problem could be in the controls for the motor. Unfortunately, diagnosing that sort of problem usually requires some specialized knowledge of the instrument's internal operations. There is an independent company, Buck Scientific, that has been in the business of repairing Perkin-Elmer instruments, although I don't know if they still do. But if you contact them, they may be able to give you some guidance on how to proceed or, depending on where you're located, perform repairs at a lower price than P-E charges. Howard \o/ /_\ | ||
| udayakumar kanniyappan (udayakumar) New member Username: udayakumar Post Number: 1 Registered: 10-2010 |
hi to all This is udayakumar. I am just entered in to field of medical physics going to findout the optical properties of tissues.My chopper perkin elmer model 651-1 which i had, the motor is not running.Warranty period is over, and it takes nearly $600 to repair that one.Is there anyother way to repair the motor in otherway or suggest me anything which will be useful for me. thank you | ||
| Francesco Davini (franz) Member Username: franz Post Number: 13 Registered: 2-2009 |
Real scientists will surely find inaccuracies in my email, but I think that I can give you an answer in general terms. It is generally true that minerals do not show an absorbtion in the NIR region of spectra. Nevertheless several mineral constituents of different matrices can be measured quantitatively with a reasonable accuracy. This is is possible because minerals (metals, ions, salts) interact with water and some organic molecules modifying their response to the NIR radiation. Also, in some matrices, the "mineral" is directly bound to an organic molecule such as in phospolipides. In other cases the presence of salts (crystals) shows a light scattering effect than can be measured. Calibrations have been developed for different matrices that measure inorganics: calcium and phosphor in feed, salt in butter or ash in (nearly) any organic product. I have no personal experience with the analysis of manure, but I can surely reccomed to choose an instrument for such application that can use disposable cups for sample presentation! | ||
| Fernando Morgado (fmorgado) New member Username: fmorgado Post Number: 5 Registered: 12-2005 |
Dear Sirs : Only when minerals are part of the matrix you can measuring it, ex plants, where minerals are part of the structure and are related ( bounded) to other components. Is easy to probe, take any powder sample and take a spectrum, after add to the same sample maybe 20% minerals, and take spectra again. Using your software make derivate of both spectra and store it. After make a spectra substraction spectra 1 minus spectra 2. The resultanting spectra will be a line, this will show not diference, and demostrate don�t minerals absorbance. Regards Fernando | ||
| Jose Miguel Hernandez Hierro (jmhhierro) Member Username: jmhhierro Post Number: 13 Registered: 4-2008 |
Hi Remci, I agree with Gustavo and Thomas Elements do not provide NIR spectra. However this technique has been used to determine some element. The results obtained for the prediction of mineral elements are not as good as for organic compounds owing to the lack of a direct relationship between the element involved and the spectra obtained. If NIRS can be used for determining mineral concentrations this is probably due to the association between minerals and organic functional groups. Best regards | ||
| Gustavo Figueira de Paula (gustavo) Intermediate Member Username: gustavo Post Number: 16 Registered: 6-2008 |
Remco, An additional note: I oversimplified my explanation - NIR can probe much more than only hidrogen. But it's a useful - and very practical - rule, anyway. Gustavo. | ||
| thomas ricour (tricour) Intermediate Member Username: tricour Post Number: 20 Registered: 2-2006 |
I agree with Gustavo. But we could also find good calibrations based on some mineral compounds in soil analysis. It is possible due to some complex with organic compounds. regards Thomas Ricour | ||
| Gustavo Figueira de Paula (gustavo) Member Username: gustavo Post Number: 15 Registered: 6-2008 |
Remco, The most probable response to your question will be "NO, It�s not measurable". The theory says that the vast majority of minerals will not be detectable at NIR wavelenghts. But you can surely see changes on organic matter behaviour due to chelated metals, as example. Also due to complex organic compounds interacting with phosphate. Even changes in water band due to minerals are theoretically possible to give information, but not easy to evaluate. Keep a simple rule in mind: NIR is a good choice for X-H bonds. Even for P-H bonds. If your target compound can change the behaviour of an hidrogen, NIR could be (potentially) used. But it doesn't work all times. You will need to evaluate your particular problem. Gustavo. | ||
| Remco Gerlich (scarblac) New member Username: scarblac Post Number: 1 Registered: 10-2010 |
I am a computer scientist / computer vision expert, working for food and agrotech business. Since our NIR expert left us some time ago I am trying to learn about the field, but I lack a really solid chemistry and physics background. We are looking into detecting mineral contents of manure, a hard problem that has been tried before, with varying levels of success. Phosphorus is a particular problem, in that it forms solids phosphate salts. Now I've heard that these are in general not measureable with NIR at all, is that true? How come? Is that true of every solid mineral or are there exceptions? |