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Thibault - owner in transition on LPF

Where to buy power meter






FireMyLaser said:
You mean this?
http://www.laserpointerforums.com/forums/YaBB.pl?num=1208710856

Too bad that it didn't caught that much attention, because I think that this can be very useful. I still use it.
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If [highlight]I HAD TO CHOOSE[/highlight] between this DIY LED/DMM and the Laserbee unit in the original post in this thread, I would build the LED/DMM. Neither one is going to be worth a crap, but at least the LED unit will only cost you $2 and some time.

Laserbee does make a unit that is "acceptable". I think we've established that it is about +- 10% accurate, but it is NOT the little "heads" he is selling now. Here is a review and subsequent discussion of THAT Laserbee unit

http://www.laserpointerforums.com/forums/YaBB.pl?num=1209516958

Matter of fact, that very unit MAY be available in the next couple of weeks. It depends on if I decide to give it to one of my friends as a gift or not. Kenom may have made it too purty to sell ;)

Save your money. Watch the group and eBay. Get a real power meter. Otherwise you are just shining your lasers in a dark room and estimating the brightness of it.

Peace,
dave
 
Yeah I meant that kind of test!

Is it true that you should use LEDs of the exact (or at least of about the same) nm as your laser? I think this is because that is the frequency it captures the best, but then again it won't really matter, since all you do is comparing volt values.

But, if you happen to have a power meter for one day, and make some measurements, you can figure out how many volts the LED will put for every mw of laser power, so you will be able to tell the exact power of your laser!
 
Is it true that you should use LEDs of the exact (or at least of about the same) nm as your laser? I think this is because that is the frequency it captures the best, but then again it won't really matter, since all you do is comparing volt values.
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At the last post in the thread I did some measurements with many different LED colours with a 532nm laser. Take a look, and you'll see that green 530nm LEDs doesn't work. Apparently.

But, if you happen to have a power meter for one day, and make some measurements, you can figure out how many volts the LED will put for every mw of laser power, so you will be able to tell the exact power of your laser!
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I've thought about that too, and that should work. Like make measurements of every 5mw or so.
BUT, there are some drawbacks. If you want to be able to test differnt wavelengths, you must make all those measurements again for each wavelength. AND the diffuser must be in the same condision (clean for ever!) at all time, or ALL the mesurements must be redone. :( So be careful with it when it's done.

I suggest that you read the whole thread about it if you haven't, and see if you get any ideas to make it better. Appreciate it! :)


Sorry for any possible spelling errors, my computer crashed and I'm now using another one with IE. :(
 
I just picked up a coherent 212 from ebay for under£50....
140230171925

The seller could only tell me the range he used it over (red to ir) so only time will tell if it will go down to the UV range, I could find no info either on the forum or the web on this model, I will keep you posted.

So to original question you need to keep looking on ebay to see if one comes up. :)

Regards rog8811
 
I've thought about that too, and that should work. Like make measurements of every 5mw or so.
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Actually it is possible that power of the laser and the mv are directly proportional, so you only need to verify that. If it's true then it would need 2 measurements of different mw lasers to determine the factor by which those are proportional and then you can calculate power output only by using the mvolts.

I read your thread which was quite interesting, still can't figure out why orange LEDs work the best (give the most mvolts). One of the explanations I read in the other thread was that you need equal or higher energy photons than those emitted by the diode in order to get some mV reading. My experiments seem to be supporting this (I have to test it more thoroughly, though), but then again that doesn't explain why your orange diode get so excited. But it doesn't really matter.

Now maybe a photodiode that will get excited by any nm of light wavelength will be most useful for this.
Plus to all those who think that this cannot be accurate, well, commercial power meters are based on this phenomenon. So you only need to determine the mW-mV curve (may not be linear), and then calibrate your device accordingly. I don't see why this won't work.

PS: Why won't someone with a power meter run a few tests, so that we can see if it'll actually be useful? (Just if you take the time to do this try to elaborate in what you measure, why etc.)
 
Now we're on the same page.

I don't think that it will be linear, so more measurements will be better. An LED is not ideal, I just used that because I could, and it start at zero mV. A photodiode or maybe even a photoresistor/solar cell will work much better, although I haven't tried it. I know that a photo resistor will be more difficult to use because it won't start at zero. I don't know if photo diodes do that, but I'll make some experiments tomorrow. The greatest advantage with photodiodes is that they can detect all available laser wavelengths, an LED doesn't.

If you want to know more about why the LED's act in the way they do, look at this thread, it is quite interesting:
http://www.laserpointerforums.com/forums/YaBB.pl?num=1208038890
 
You could have a chart with pictures of the dots at 10mw increments than you could compare yours (:
 
hahah that's like taking a picture of a light bulb and askin folks to guess the wattage.
 
... well i have read a blog on making your own LPM but the only way to calibrate it is with a LPM that has already been calibrated ...

if someone of some reputation were to be building these LPM for say under $50 i would defiantly consider buying one.

the blog i saw was using solar cells to detect the beam.
 
No one would be able to build them for $50.

People have been trying for years to find a cheap easy way to assess power, but there just isn't a good solution yet :-/

I picked up my LPM for $200, and it does a great job :)
 
I bought the 120mw power meter.As far as i can tell it works but i don't have any thing to compare to.Their is a chart to tell you how much to x by for each wavelength.it tells me my jasper apc is 4.87mw.My true 30 35mw.
 
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