Power Meter Calibration and Comparison

here is the actual physical readings per 60 seconds.

Kenom said:

No lazors?  that's not a good thing.  I don't know for sure that the krytons will be to you by the time that it gets to ya.  The reason for laser as a requirement is so taht you won't be tempted to play with the calibration lasers for anything other than testing.  So you might want to consider your participation in this.  Not saying you can't unless you aint got lazorz.

Ok I've got my two setup and they are lasing.  I'm looking at how long folks are wanting to test these things for average?  30 seconds?  1 minute?  Only reason I ask is I'm lookin for stability.  The bluray has been set to 102mw but after a minute it does increase a mw or 2.  Seems to keep increasing as well.  I'm doing some testing on stability

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I can promise I won't play with the laser, but if you don't want me to do this that is fine also. SO who do I need to pay and how long do I need to run this test for?

I did a run of four days, measuring the laser as it ages, and these are my preliminary results. White squares are measurements during the day, black ones during night. It's very clear that measurements during the day give wrong results (on my thermal meter) When I think of the weather the past days, I remember that yesterday (at ~48 hours) was a little colder and four days ago when the measurements started, it was a very hot night. I still think that there are not enough measurements to say this for sure, but it looks like it once again proves the importance of temperature (and not the age of the laser).

I will continue aging and recording my laser for now. I will also start taking measurements from another laser (identical diode, different host), which I will not age.

As it looks right now, I still think the best solution of preventing bad readings from temperature fluctuations is to create your own stable reference laser (of each color) so you can generate a temperature correction factor every time you measure something.

Really looking good there Kenom. Great job!

I know I won't be looking inside. Wouldn't want to be the guy that screws up the experiment! My new meter shipped yesterday!
Jay

Kenom - you brought up a good question - what effect does the ambiant temperature have on the power measurments?

Would we expect enough variation in the measurement from the room temperature to moot the variation from the calibration meters?


Mule

Ambient temperature does influence the results. That's why it would be good to determine a base temperature, and people would try to get as close to it as possible, when doing the testing..
AC can help, but probably shouldn't be on during the measurements, to avoid having air currents affect the results.

It should be a temperature everyone can reach, if not with AC, then simply by waiting for the night...


It might also be good, if there was a field next to the measurement results, to record the temperature during the tests.. Like "Temp: xx°C Regulated? Yes/No"

Maybe just a little digital thermometer to include in the kit to record room temperature? Then just write down other conditions in our test notes...
Jay

I agree on both.

jayrob said:

Maybe just a little digital thermometer to include in the kit to record room temperature? Then just write down other conditions in our test notes...
Jay

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Great idea Jay!

It would definitelly be better, if everyone uses the same thermometer to determine the temp..

I have one of those cheap IR thermometers that tests whatever you point it at.  This is what I used to measure the temp in my room.  I can sure ship it along.   For me to get temp at about 75 I have to wait until 4am or so.  I did turn off my a/c prior to the testing.  let the air currents stabilize.  I'm going to set the focus around 1mm-2mm on each of these at 6" then glue the lenses down.

Now ambient room temperature DOES affect the thermal meters BUT NOT the optical one's. Obviously if you have a lpm-1 heat isn't going to affect a silicone light sensor. Temperature is probably going to be the one and only thing that is going to be difficult for us to regulate. We can set the temp in the room as best we can but never does that temperature stay regulated. There will be fluctuations in the temp and in the readins. but it's not going to be that much. we still have a percentage of calibration that it's going to be off and it's not going to be all that much. You can see from my readings that it's really not all that much.

Temperature will certainly affect optical meters. How much is the question, and whether or not it will matter in what we see or don't see. Optical meters measure the carriers generated by the light. Carriers are also thermally generated, so higher temperature means more more carriers, by necessity. How much this affects your meter/sensor depends on your meter, but it's not accurate to say it has zero effect.

This afternoon I tried to measure my laser with measurements of 30 seconds each, and after every measurement I had to adjust the zero because it had drifted by as much as 1mW (my resolution is 0.1mW). The difference between minimum and maximum readings was almost 2 mW! The weather was partly clouded and sunny, creating alternating shade and sun on my workspace.

Kenom said:

I have one of those cheap IR thermometers that tests whatever you point it at.  I can sure ship it along.

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Include in the package a used rectal thermometer for the customs guys if they want to "poke" around in the package



Mule

ok she's ready to ship off with the exception of one thing. I ended up cutting into the wire below the heatshrink tubing so I'm going to replace the heatshrink tubing. I'll also include the thermometer. The lens has been glued into place with some thermal silicone It's easily removed but such that you can see if it's been tampered with. The head is GORILLA glued into place. It'll come apart but it will take a LOT of work. I set both focuses at about 6" so anything beyond that the focus will be off.

I will ship this off to pseudo tomorrow. Then let the testing begin

Kenom said:

ok she's ready to ship off with the exception of one thing.  I ended up cutting into the wire below the heatshrink tubing so I'm going to replace the heatshrink tubing.  I'll also include the thermometer.  The lens has been glued into place with some thermal silicone  It's easily removed but such that you can see if it's been tampered with.  The head is GORILLA glued into place.  It'll come apart but it will take a LOT of work.  I set both focuses at about 6" so anything beyond that the focus will be off.  

I will ship this off to pseudo tomorrow. Then let the testing begin

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How is the shipping order to proceed? Are we following the list in the Google docs? If so, I guess each person will contact the next person on the list for their shipping address huh?

What do you think Kenom? Maybe fix the list in Google docs for a shipping order? Also, I did not see your measurements in there...
http://spreadsheets.google.com/ccc?key=pW49OuYfRMm7FXsb9trxWdQ&hl=en
Jay

So, if I want to calibrate my meter, I should join this? or is it too late?