Power Meter Calibration and Comparison

danq · Jul 28, 2008

danq said:
re: physical setup - am I correct in presuming that a reading will be more accurate with the beam spread out over a larger portion of the sensor, rather than focused into the smallest point?
if so, let's be sure the fixed focus makes a decent beam that fits into the [highlight]LASERBEE thermopile [/highlight] at the prescribed distance...

daguin said:
There. I fixed it for you

oh... sez on the spec page that's 8.5mm x 6.0 mm... 6mm is roughly 1/4 inch - pretty small :-?

GooeyGus · Jul 28, 2008

is focus really an issue? I've never been able to skew my readings with focus whether the dot was focused to burn or if it was as big as the sensor. Either way the same amount of energy is going to the meter, just over a greater/lesser area.

rkcstr · Jul 28, 2008

No matter the focus setting, it should be constant for everybody since we would be agreeing on a set distance for measurement.

muledeer · Jul 28, 2008

jayrob said:
Kenom will be collecting the money when the list is done. This automatically makes Kenom the organizer of the list, and who has paid.

Kenom, sounds like we already have 4 potential contributors!

U.S.:
jayrob
daguin

Then Europe:
Zom-B
IgorT

Let's see some more people get in on this! You out there electron? We know you just got an awesome meter...
Jay

Man this thread mushroomed!

I'll kick in some costs -- I do not have any measurement equip but am willing to help bring the cost down - I just want to see the results, because if the variation between devices is minimal, I can be comfortable buying any type available.

Mule

Kenom · Jul 28, 2008

I don't think we're going to get a cheaper host that is going to provide sufficient heatsinking without going to either a Kryton barrel or a jayrob Mxdl with Jayrob heatsink. The Heatsink would bring the cost up to equivelent what we're spendin on the dorcy. I honestly don't care one way or another. I know that my dorcy jr's with heatsinks are not the best and most efficient heatsinking but it's better than just a blank aixiz.

IgorT · Jul 28, 2008

At 100mW, the small heatsink in a Dorcy would be enough. These diodes dissipate just under 0.6W of heat at that power, and reds even less.
The laser should still be left to cool off for a minute, between measurements.

Otherwise, the fixed focus should be set to a parallel beam. Not diverging. It doesn't matter to a thermopile, and it doesn't matter to a photo-cell. And if it did matter, it would be even more important to have a parallel beam, otherwise the distance would be too big a factor. A spreading beam could also be too big for optical sensors..

danq · Jul 28, 2008

GooeyGus said:
is focus really an issue? I've never been able to skew my readings with focus whether the dot was focused to burn or if it was as big as the sensor. Either way the same amount of energy is going to the meter, just over a greater/lesser area.

Ah.. I hadn't tested it, glad somebody knows. Then as Igor said, parallel is best.
And since Kenom will be building it; and his usual build is the Dorcy; and if consensus is that seems to be enough heat-sinking - sounds like that's the way to go.

Zom-B · Jul 28, 2008

danq said:
re: physical setup - am I correct in presuming that a reading will be more accurate with the beam spread out over a larger portion of the sensor, rather than focused into the smallest point?
if so, let's be sure the fixed focus makes a decent beam that fits into the smallest meter's aperture at the prescribed distance...

No. When the spot size is increased, the reading actually drops on my thermopile sensor (because stray light from the lens widens too) and when focusing it to a tiny spot, the sensor is locally overloaded (they can take a maximum amount of Watt per square <insert length unit here>). For example, the Coherent LaserCheck can have at most 0.5W/cm[sup]2[/sup] before damage occurs. Focusing 100mW on a tiny dot, like 0.1mm (in reality, might be smaller) the light density is 0.1/0.01[sup]2[/sup] = 1000W/cm[sup]2[/sup].

Lets just keep the beam focused at infinity. Every meter's aperture should be big enough for this.

danq · Jul 29, 2008

well... that's more or less what I was thinking, about the focused dot anyway - overloading the sensor locally.

jayrob · Jul 29, 2008

Kenom said:
I don't think we're going to get a cheaper host that is going to provide sufficient heatsinking without going to either a Kryton barrel or a jayrob Mxdl with Jayrob heatsink. The Heatsink would bring the cost up to equivelent what we're spendin on the dorcy. I honestly don't care one way or another. I know that my dorcy jr's with heatsinks are not the best and most efficient heatsinking but it's better than just a blank aixiz.

I agree that Kenom's offer to build two lasers at 'cost' is not only very inexpensive (not to mention very generous), but I like the size of the lasers for shipping. I'm sure they are plenty good for heatsinking. (plus I want to see his build)!

But if you want more heatsinking, and a very inexpensive and really easy build, check out my latest tutorial for a $6 dollar MXDL host with a side button clicky:
http://www.laserpointerforums.com/forums/YaBB.pl?num=1217045236
I would have no problem donating the two heatsinks as my contribution to this project... I want in early on the list though!

Jay

Kenom · Jul 29, 2008

I've already got two laser hosts already setup with heatsinks, and just need to put in diodes and flexdrives. I'll kibosh it though if folks wanna go with the mxdl. I don't think the additional heatsinking will be necessary TBH

jayrob · Jul 29, 2008

I too think Kenom's builds are just right.

But, as another option, I will offer to donate the red build for $40 bucks. (just the cost of the FlexDrive and the LD) I'll donate the side button MXDL and heatsink, build it, and send it to Kenom. The blu-ray wouldn't need as much heatsinking.

Again, I'm good with any way you guys want to go. I just want it to get started!

Jay

IgorT · Jul 29, 2008

If both lasers are set to 100mW, the red will actually dissipate less heat, than the blu ray.

For the blu ray at 100mW, it's 0.575W, and for the red, it's around 0.36-0.4W of heat.. Hardly worth mentioning.
Or is the red gonna be set to 200mW? Also, both lasers should be set to 100mW by the same person on the same meter. Otherwise the results won't be usefull.

scopeguy20 · Jul 29, 2008

O.K. first I want to thank IgorT for telling me this was being planned. And thanks to Kenom and all the other contributors of ideas and participation alike. I would definitely like to be a tester, and want to be on the end of the line, (Just before return to the 1st person), if it works out better. I ask that, as I am about to leave for a summer vacation in the mountains for 2 weeks. So I don't want to hold up things if the test lasers are going to be sent around before I'm back on Aug 16. I usually say my Kenom Thermal LPM is about +/- 4% as it agreed with a more recent built die4things to better than 2% on over a dozen lasers, but this test would give us more certainty. Thanks again!

Kenom · Jul 29, 2008

We could ship along a log, with the instructions and the readings from all of the meters. Oh this is going to be fun.

Kenom · Jul 29, 2008

Oh and my paypal issue has been resolved.

Power Meter Calibration and Comparison

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