Power Meter Calibration and Comparison

Kenom said:

Still waiting anxiously for the completion of the initial comarison by pseudo and then the passing of the lasers to the first on the list (daguin)

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What's the word pseudonomen137? Are the lasers already on the way to Dave?
Jay

Ya know this is getting rediculous. I understand that we get busy and being a student makes for a lot on a persons plate, yet I manage school, 2 kids, and the GB stuff and regular activity on the forum. There is no reason that a reading that takes a few minutes, should take a few weeks. There are a lot of people waiting to get these lasers to test and calibrate thier laser power meters and having to wait on you pseudo is beginning to be a norm that shouldn't be for someone trying to sell lasers.
Ken

[impatient mode] pseudo, get your lazy azz back here and at least say something. If you have nothing to say to us then we can only assume that something obscure is going on with the lasers that can't be talked about.

jayrob said:

The LPM-1 seems to be pretty accurate with the wavelengths that it has been calibrated for though.

If anybody else has made similar comparisons, please post!
Jay

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Problem is, even optical meters with a calibrated 405nm setting show up to 45% too much! Due to the sharp cutoff of sensors and glass, never mind plastics, at just around 400nm, a tiny difference in wavelength can make a huge difference in transmittane or sensor response..


I recently made one of my blu rays for Daedal, and since he has an LPM-1 i asked him to do a measurement on all the meters he can find, but especially the LPM-1... I selected a diode that did an unusually high wavelength on purpose, just to see what would happen.

After measuring the laser on the LPM-1 and a thermal meter, he came to the conclusion, that a multiplier of 2.74x would be required for the LPM-1 to show correctly, in the 473nm setting with the ND filter..


For an optical meter to measure any wavelength preciselly, it would also need a spectrum analyser, and then it would have to measure the wavelength, and the voltage produced by the sensor, and calculate the power from a wavelength response lookup table. For wavelengths, where the sensor response differences are small, the result will be pretty accurate, even if you simply guesstimate, that a red will do 660nm. But you just can't rely on an optical meter, when measuring blu rays. Not when diodes vary in wavelength so "much". Well, little actually, but this little has a huge impact.


Anyway, Jay, did you notice the same behavior? Higher wavelength, higher multiplier needed? Cos with some blu rays, the correct multiplier can be under 2x. Is that with shorter wavelength diodes, or the other way around?

shorter wavelengths need higher multipliers since less light is converted to voltage.

Just tried making a photo through my diy spectroscope and it works out pretty well

Igor, I pretty much don't even use my LPM-1 anymore. I have no way to be sure of the exact wave length either. (just visually bluer, or brighter)

Looking forward to this comparison experiment, but has anybody heard from pseudo?
Jay

Zom-B said:

shorter wavelengths need higher multipliers since less light is converted to voltage.

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That's what i thought as well. But then why did Daedal get a higher multiplier?!? :-? I selected a high wavelength on purpose, expecting a lower multiplier, not higher....

I thought my powerful one had a shorter wavelength too because it is 3.6 times more powerful according to my thermal meter, but to the eye, it looks 10 times brighter. And that's only when shining on non-fluorescent materials. Fluorescing light looks about 3.6 times brighter also. I was surprised too to find it actually has a higher wavelength.

I got a package today (unannounced) from Pseudo. The lasers are acclimating to the house now.

Peace,
dave

Let's try this again . . . .

The spread sheet won't let me add any info to it

10/09/08

daguin

Scientech 365 (set to the 200mW range) -- Scientech 36001 calorimeter

660nm -- 5sec = 122.3mW -- 15sec = 122.1mW -- 30sec = 122.0mW

405nm -- 5sec = 65.0mW -- 15sec = 65.0mW -- 30sec = 65.2mW

Ambient temp = 76.6 (f)

In my office, on my desk, three @ CFL on ceiling, house air conditioned, air conditioning vent closed to this room for test.

The lasers arrived without dust caps, but inside individual anti-static bags

PM sent to ScopeGuy20

Peace,
dave

Kenom said:

I'm not going to guestimate at what's causeing the low current but it's set at 75mw exactly.

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Kenom: 75mW
daguin: 65mW

Average: 70mW
Standard deviation: 7.1mW
% standard deviation: 10%

Two data points, and we already have >10% standard deviation, wow.  (I know statistics don't mean a lot with only 2 data points, but with only 2 data points, there shouldn't be that much variation. That the stdev is that big already is crazy.) Both measurements on the same model thermal meter.  This could get interesting.  Still no word on what psuedo measured?

The red is better, both within 1% of the average and just a little more than 1% standard deviation.

And Dave's meter is higher for red, but lower for violet. We'll see what we get when we have some more data.

pullbangdead said:

Kenom: 75mW
daguin: 65mW

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We need Pseudo's measurement.

We also need access to the spread sheet. I believe Rkcstr made the sheet. Does it need to be opened up to us or do I need to do something besides sign in to Google?

Peace,
dave

Dave,

PM Ken with your email address and he can add you in the spreadsheet.

You've been added dave.  I'm a bit intriqued about the variance thus far.

Oh and other than the reds reading from psuedo you wont' get a testing for the bluray from him. he was taking too long to test it so I asked that he ship it directly to Daguin. I'd rather see this continue to move forward than have to wait for him any longer.

Are the numbers written on a piece of paper or something?  :-?


EDIT: Oh, i see...