Power Meter Calibration and Comparison

[jayrob]

Jayrob: How long does the power remain stable (as in, doesn't drop from the original number by 1mW) with a red at 250mA, and one of your massive heatsinks?

If it can keep the "exact" same power for over a minute, and we follow the suggested protocol with short measurements, the increased resolution could be beneficial.

Well, I don't have such a build to test. However, I do have some high range FlexDrives, and could set up a build like this. What I do have, is my personal FlexDrive build that has an open can diode at 448mA's. (I'm sure 250mA's would be much less heat than 448mA's)

I have it labeled at 260mW's.

I just tested it for 2 minutes with my LPM-1 optical meter.

It started out at 274mW's as an initial peak. It held at 270mW's for about 15 seconds, and then slowly dropped to 250mW's with in the next 45 seconds. It stayed at 250mW's for the next minute of the 2 minute test...

Correction! I should have known better! In the above test, I thought that I could just hold it steady enough with my hand, but I found on the second test (laser and meter resting on the desk), that it was stable at 258.1mW's through out the test.

With the LPM-1 optical meter, just the slightest movement changes the reading... I know, I should have known better, but when I'm holding the laser by hand, I can angle it a little to get the highest reading... ;D
Jay

 

[Kenom]

LOL. Is the reliability of the initial testing and setting of the laser (say to 100mw each) going to matter a lot? I've got two meters (kenometer, and a scientech that has recently been calibrated by knimrod) that I can do a basic comparison between both meters when the lasers are constructed and set to make sure that the initial power output is stable. Then would we want to do some kind of testing on the laser over a period of time to determine that the laser is indeed stable and not prone to dying while being used for these tests??? Like running the laser for 45 minutes straight turn it off for 5 then back on again for 45 and so forth.

Another thing is some of these meters have a method for zeroing based on temperature and it's pretty important as it's hard to regulate a temperature in a room short of having an icebox insulated and can run our tests inside there. Theoretically as long as your temperature is stable with no fluctuation and your meter has an offset for zeroing (not all do) then temperature isn't going to be much of a factor. Have we decided what host it's going to be built in? I have every intention of making the laser over 100mw on the red (probably in the neighborhood of 130-150mw) and the bluray spot on 100mw or a fraction above if possible)

 

[Kenom]

Oh and my red set at 250mw is stable over 5 minutes never decreasing so much as 1mw.

 

[jayrob]

I just did the same 2 minute test with this Kryton/FlexDrive build, and it was totally stable for the entire 2 minutes.

268.1mW's...no fluctuation. Must be some good heatsinking in that design! Wonder who designed it? :
Jay

P.S. I do believe that the one drawback of a Meredith module besides the price, is that it obviously is not as good for heat transfer to the heatsink. The 5.6mm adapter is just sitting against the module case with spring tension. So a 'pressed in' design, such as an AixiZ, or the awesome Kryton, is much better for heat transfer...

 

[danq]

Don't you just love listening to scientists talk?

yeah, but sometimes dontcha just wish they'd shut up and do the experiment?
c'mon, when do the pretty lights start?

 

[Kenom]

that jay was the primary reason for the design in the first place. The heat transfer from copper to brass to aluminum just had too many changes in metal for it to be efficient for me. So you reduct it to just copper to aluminum.

 

[jayrob]

that jay was the primary reason for the design in the first place.  The heat transfer from copper to brass to aluminum just had too many changes in metal for it to be efficient for me.  So you reduct it to just copper to aluminum.

They are the BEST! I have two 1st run Kryton's that I'm keeping (one blu-ray, and one red), and two Kryton Grooves coming. These too, I will never sell...
Jay

 

[hydro]

I need some clarification, are we looking at both thermal-pile and optical meter type together or separately? Unless one has an optical meter calibrated specifically for that wave length it will just be a guest. I know people use a correction factor but how accurate is that factor? Also from what I remember from statistic we will need at lease a population sample of 30 for an accurate assessment base on the Central Limit theorem.

 

[jayrob]

I need some clarification, are we looking at both thermal-pile and optical meter type together or separately?  Unless one has an optical meter calibrated specifically for that wave length it will just be a guest.  I know people use a correction factor but how accurate is that factor?  Also from what I remember from statistic we will need at lease a population sample of 30 for an accurate assessment base on the Central Limit theorem.  

I'm sure that there will be much that can be learned from this experiment. I think that the most of us are interested in learning the average, or as close to accurate measurement that the lasers really are. That way, we can take our individual readings, and know what  multiplier to use, in order to have an accruate stated output...
Jay

P.S. You and Dave are in So. CA, and I'm in No. CA

 

[hydro]

This experiment has too many variable but we still need to set some guide lines to obtain the best possible outcome. I think one of the more important one is the type of meter to be include in the data sampling. If we use both type (thermal and optical) then the data should be kept independent and only the average should be compare at the end. This way people with multiplier will still be able to compare there value with other optical meter and thermal type meter. So if you know your multipliers then you are still able confirm that your reading is accurate or not. But if you are not sure of the multiplier values and the sampling is used in the data then the outcome will not as accurate.

 

[GooeyGus]

What if we have more than one meter? For example, I have a scientech 362 and a 364, should I do separate tests for both or just use one of them to submit my results?

 

[IgorT]

You are right, Hydro. If we decide to use the average as the most accurate reading, then the thermal and optical readings have to be kept separate for analisys. Otherwise it would skew the results too much, because even optical meters with a callibrated 405nm setting can show 30% more than any thermal meter.

But i'm still hoping we can get some high accuracy meters into this, and then use that average as the baseline for adjusting everything else.


But for now we just need testing guidelines. If the results are recorded correctly, we can do any postprocessing we want. That can still be agreed upon later.

 

[IgorT]

What if we have more than one meter? For example, I have a scientech 362 and a 364, should I do separate tests for both or just use one of them to submit my results?

I think you should use both, and write down which was which. Everyone should write down the meter(s) they used for the test, next to the readings..


Otherwise, what differences did you notice between the two meters?

 

[jayrob]

[quote author=GooeyGus link=1217029972/120#122 date=1217406266]What if we have more than one meter? For example, I have a scientech 362 and a 364, should I do separate tests for both or just use one of them to submit my results?

I think you should use both, and write down which was which. Everyone should write down the meter(s) they used for the test, next to the readings..


Otherwise, what differences did you notice between the two meters?[/quote]

For sure, for sure... We will end up with a list of readings from many different meters. If you have more than one meter, that's just more information we will have for comparisons!

hydro, I agree. For those of with optical meters such as my LPM-1 (which does not have a 405nm setting), the blu-ray information should be written down as the 473nm ND filter reading (if over 100mW laser) The multiplier can be figured out later, by individual testers, based on the gathered information.

As far as separation, this will be a list. Anybody can organize the information at a later time, as long as all the information is recorded...
Jay

 

[hydro]

Perfect, two sets of data one for the thermal and one for optical.

The more sampling of data we have the better the result just as long as we note the different types of meters.

 

[danq]

pls forgive me if this is slightly out of line...but I thought the primary purpose of this is for each of us to be able to calibrate our meters, so when we report a power reading later, it will be accurate... kind of like synchronizing our watches.

Of course a nice side-benefit is we will have data on different meters - and I will of course report my meter's readings before I adjust it - but then I will adjust mine to the 'standard'.

I'd like opinions on whether these basic procedural blocks are what y'all have in mind:

• get my meter as accurate as I can, with what I've got here
• receive the 'standard' laser(s) in the mail
• measure the 'standard' laser's output prior to adjusting my meter
• adjust my meter to read the standard-bearer's set value (or that of whomever is thought to have the most accurate meter so far)
• pass the 'standard' on to the next person
• report my measurements
• later, when everybody has posted their results, decide whether the standard-bearer's measurement was accurate
• if not, adjust my meter to reflect the new (computed) reading that should have been the standard reading.

sound good?