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Join Date: Feb 2009
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Data Acquisition of Light Emittance

02/12/2009 10:24 AM

Im looking for an efficient and reliable way to measure light emittance at a specific point on a centrifuge from a source as it spins at 14,000 rpm. Does anyone have any ideas on how I could do this? And what type of materials would be needed for this measurement?

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#1

Re: Data Acquisition of Light Emittance

02/12/2009 12:40 PM

sdonahue199,

Are you trying to "see through" just one of the tubes? If so, is there a point in the revolution that you isolate that between two points? If so then you can use an LED/phototransistor pair and tune for how much transmittion gives you your result.

This will also need to be "strobed". It needs to activate for a on-shot every time the tube is between the LED and phototransistor.

For an expensive solution, you could look into vision systems.

Mike

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#2

Re: Data Acquisition of Light Emittance

02/12/2009 3:51 PM

More information please.

Do you need spectral information or just the integrated light energy? They are very different.

Look up "Hofman" cells if it's just light energy.

Also look up "Photomultiplier tubes" to find suppliers of the type of equipment that you are after.

Manufacturers like "LMT" have devices for precise light measurement.

Depending on the intensity of your light source and the precission that you require will very much determine the sophistication of the equipment required.

In your measurement field of view there must be ABSOLUTELY NO other light sources or reflections and even heat sources (like hot bearings) can appear as visible light due to a "frequency doubling" effect that is not accounted in some cheaper devices.

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#3
In reply to #2

Re: Data Acquisition of Light Emittance

02/13/2009 10:26 AM

If this centrifuge is spinning at 14,000 rpm, and you just need to measure one part of each cycle, then you are probably looking at a detector with a very fast rise time and high sensitivity, since their may not be a lot of light energy to collect in such a short amount of time. If this is the case then the photomultiplier tube will probably be the best choice. I believe that Hamamatsu (and perhaps others) makes a module with the PMT, power supply, and pre-amp, all in a neat little box. It is powered by and sends its output directly through your USB port.

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