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FrozenGate by Avery

Incredible! Semi-Accurate Results from Free LPM?!?!






This is a great proof of concept! It would be interesting to compare your results with a calibrated LPM. However I would not be surprised if the error of this is as much as 30%. Also remember, LPMs made with TECs are likely not accurate to within a tenth of a milliwatt. I suspect even they have an error of up to 10%.
 
Thanks!

I thought that the Laserbee and the Kenometer both used TECs, just high-grade ones?
 
Pretty cool Concept.

Your 532 Dont know.:thinking:
Your LOC No way. Thats ~70mW off. at 380mA you LOC should be ~180mW. At 420mA an LOC is Between 220mW-~250mW.
445nm Sound Good.

Dont know How accurate this is but if you have a buddy or someone with a LPM near you, Then you can compare your Results on a know accurate meter to see how they match up.:)
 
I can recheck the measurement on my LOC :P I had a hard time getting this one right because my goggles aren't red-blocking :P

Unfortunately, the closest person with a LPM that I know is Dave and shipping there and back would still be 40$ if I wanted my lasers to be guaranteed safe :\
 
Lasersbee and Radiant Alpha LPMs both use TECs as far as I am aware of, lasersbee please correct me if I am wrong. Remember that TECs are intended to be used in reverse as heat transferring devices, but can be used to measure transfers of heat.
All of the kenometers I am aware of use high quality, pre-calibrated thermopiles that are intended for laser power measurement. The latest version of kenometers use the OPHIR 20C-A thermopiles.
 
Wolfman29 said:
But I heard that the LED LPM is not nearly as accurate as the TEC LPM?
Click to expand...

we are comparing Solar Cell LPMs against LED LPMs...
because they are cheap... (your main criteria above)

Thermopile LPMs are another animal... with their own
inherent quirks...

Jerry
 
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Wolfman29 said:
I can recheck the measurement on my LOC :P I had a hard time getting this one right because my goggles aren't red-blocking :P

Unfortunately, the closest person with a LPM that I know is Dave and shipping there and back would still be 40$ if I wanted my lasers to be guaranteed safe :\
Click to expand...


Just make a Cheap LOC or PHR in a Project box. With a LM317 Driver and 2 14500 cells.

i am sure Dave has some 14500 cells so you dont have to ship those to to keep the weight down.

This laser should Cost you ~$10-$15 dollars to build.:)
 
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laser_freak said:
This is a great proof of concept! It would be interesting to compare your results with a calibrated LPM. However I would not be surprised if the error of this is as much as 30%. Also remember, LPMs made with TECs are likely not accurate to within a tenth of a milliwatt. I suspect even they have an error of up to 10%.
Click to expand...

FYI.... our LaserBee products follow our NewPort 1825C Laser
Power Meter to within 2% or better when we calibrate them...

EDIT
laser_freak said:
Lasersbee and Radiant Alpha LPMs both use TECs as far as I am aware of, lasersbee please correct me if I am wrong. Remember that TECs are intended to be used in reverse as heat transferring devices, but can be used to measure transfers of heat.
All of the kenometers I am aware of use high quality, pre-calibrated thermopiles that are intended for laser power measurement. The latest version of kenometers use the OPHIR 20C-A thermopiles.
Click to expand...

The Alpha and the LaserBee 2.5W USB LPMs use a similar
inexpensive TEC in the Seebeck effect mode... just like the
Scientec Thermopiles.

A TEC used in the Seebeck effect mode is still a Thermopile by
definition. It uses dissimilar materials to make a thermocouple
and a series of thermocouples make a thermopile.

The old Kenometers used an old surplus Coherent head and
the newer Pro...5W Nospin and Limited Edition 5W LaserBee
meters used surplus but newer OPHIR 20C-A heads...
The Coherent heads were calibrated by Coherent to 1uV/1mW.
The OPHIR heads were calibrated by OPHIR to 1mV/1mW...
so all you really needed to make them into LPMs is a Voltmeter.

The sensors used in the LaserBee products that have an on
board LCD... are manufactured by a company to our specs and
are more expensive... accurate and respond faster that the Alpha
or the LaserBee 2.5W USB LPM Thermopiles...


Jerry
 
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Oh. In regards to Solar cell vs. LED: I don't have any LEDs around (that I know of) and I just happened to have this spare solar cell lying around.

In regards to shipping... the idea was to ship my three lasers to Dave so I could have them accurately tested, completely separate from this project. However, if I had them accurately tested anyway, it would help me.

Unfortunately, I am not allowed to spend any of my money right now =[
 
"My solar cell is a generic solar cell."
Solar cells have 2 modes of operation: voltage and current. For use as a photon detector, you must use it in a current mode; that is, you need to match the low impedance of the cell to a low resistance to force the cell to be linear. A great read on the subject for background is: "Photodetectors and solar cells" by: Khanh Kieu (12/03/2009) which can be Googled and downloaded as a PDF.
Lasersbee is one of the forum experts and sells an optical power meter based on PIN diode photon to current conversion.
No one is trying to dampen your enthusiasm for using a surplus solar cell, but ensure you use only one "cell" and not an array of cells in series since this will greatly affect your accuracy. For any given wavelength, you should be able to do the math and have a nice unit for comparison of two lasers of the same wavelength or even to compare modifications to a single laser, say monkeying around with a green cheap-o. Remember to filter out any IR from the green however since you can get some nasty invisible reflections off the solar cell surface.

Ray
 
Oh. Thanks for that information! Since I constructed this thread, I actually built a TEC-based LPM that gives me slightly more accurate readings (and by slightly, I mean significantly), so... there it is :P
 
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