Timeline for How is a spectrometer is calibrated for intensity?
Current License: CC BY-SA 4.0
20 events
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| Oct 15, 2019 at 12:01 | comment | added | Michael Seifert | Well, keep in mind that this was a teaching lab, where the equipment might not have been re-thought or revised over a span of many years so long as it worked "well enough". I went into a very different field of physics, and for all I know there are better options out there. | |
| Oct 15, 2019 at 9:02 | comment | added | Ömer Gezer | @MichaelSeifert Okay I missed that you mentioned using a pyrometer. I never had luck using those correctly but if it's the way to go, I'll look into that. | |
| Oct 15, 2019 at 8:56 | comment | added | Ömer Gezer | @S.McGrew The only photoelectric devices I know are photodiodes(which includes phototransistors, leds and solar cells). Yes, their output is proportional to the incident photon flux for a single wavelength, but the ratio differs among wavelengths. Their wavelength sensivity characteristics are given in their datasheet, but without any tolerance. They are generally used as the detector in a spectrometer. But the problem is, the other parts in the spectrometer heavily contribute to its spectral response and I can't easily predict it, so the spectrometer in whole need to be calibrated. | |
| Oct 15, 2019 at 8:46 | comment | added | Ömer Gezer | @MichaelSeifert I'm looking to calibrate relative intensity across wavelengths, I won't be needing absolute intensity values. My interest is color measurement. Using tungsten emissivity data at specific temperatures seems interesting, if it's spectra is known and consistent at certain temperatures, that would be useful. But how could i (somewhat)accurately measure a tungsten filaments temperature in a bulb? | |
| Oct 15, 2019 at 3:12 | comment | added | S. McGrew | Haven't researched this, but it seems that the photoelectric effect could be used to (intensity) calibrate a spectrometer, since its output is proportional to the incident photon flux: britannica.com/science/photoelectric-effect. "Devices based on the photoelectric effect have several desirable properties, including producing a current that is directly proportional to light intensity and a very fast response time." | |
| Oct 15, 2019 at 3:00 | history | tweeted | twitter.com/StackPhysics/status/1183940563608973312 | ||
| Oct 15, 2019 at 1:07 | comment | added | Michael Seifert | Also: are you looking for a way to ensure that (say) 0.01 W/m<sup>2</sup> of intensity creates the same size peak at 400 nm as it does at 600 nm (i.e., calibrating relative intensity across wavelengths)? Or are you looking for a way to associate absolute intensity readings with a particular response in your spectrometer? The two are somewhat different questions. | |
| Oct 15, 2019 at 1:04 | comment | added | Michael Seifert | I have a recollection of doing a calibration along these lines for a Raman spectroscopy lab during my graduate-level experimental physics course, c. 2005. This involved (a) taking the spectrum of an incandescent bulb in the spectrometer, (b) using an optical pyrometer to measure the temperature of the filament, and (c) looking up data on the emissivity of tungsten. I honestly don't recall how accurate the results were, or indeed whether we did a very thorough error analysis on the calibration curve. | |
| Oct 15, 2019 at 0:21 | history | edited | Ömer Gezer | CC BY-SA 4.0 |
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| Oct 15, 2019 at 0:08 | comment | added | Ömer Gezer | @mmesser314 I indeed plan to use the device to experiment with color measurement too. I hope the technology has advanced enough in 40 years so we don't have the same difficulties as before. I wonder if i can just use a white LED from a reputable company which lists its spectral properties for given temperature and current. How accurate would such an intensity reference be? | |
| Oct 14, 2019 at 23:58 | comment | added | mmesser314 | Early in my career, ~1980, I worked for a company that made color measurement instruments. Intensity calibration was a problem. We bought an incandescent light bulb from the National Bureau of Standards that they can calibrated. It was good to about 1%. It was expensive and we treated it very carefully. We kept it in a safe place, used it seldom (to calibrate secondary standards), and ramped the voltage up and down slowly when we did. I think the NBS had calibrated it with their own special light bulb. | |
| Oct 14, 2019 at 23:48 | history | edited | Ömer Gezer | CC BY-SA 4.0 |
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| Oct 14, 2019 at 23:43 | comment | added | Jon Custer | Perhaps editing to clarify the question would be good. Calibration of intensity is harder since there are many variables just in getting light through the spectrometer. | |
| Oct 14, 2019 at 23:40 | history | edited | Ömer Gezer | CC BY-SA 4.0 |
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| Oct 14, 2019 at 23:37 | history | edited | dmckee --- ex-moderator kitten |
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| Oct 14, 2019 at 23:35 | comment | added | Ömer Gezer | @JonCuster Okay, so as far as I found, those are used to calibrate the wavelength accuracy of the spectrometer. I didn't specify in the question but i was talking about the amplitude calibration. Those sources seem to emit light at very specific bands so they can be used as wavelength reference | |
| Oct 14, 2019 at 23:33 | comment | added | The Photon | I've seen mercury (IIRC) lamps sold specifically for this purpose. | |
| Oct 14, 2019 at 23:28 | comment | added | Jon Custer | 5% is a pretty lousy calibration. Various gas emission line sources are easy to get and use. | |
| Oct 14, 2019 at 23:25 | review | First posts | |||
| Oct 15, 2019 at 7:53 | |||||
| Oct 14, 2019 at 23:22 | history | asked | Ömer Gezer | CC BY-SA 4.0 |