Power Meter Calibration and Comparison

Kenom said:

does it matter if it comes from a european country or just the united states?  Because I know that happytomato would be happy to pass it on from him so taht this doesn't happen if you don't get nailed from european countries.

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That WOULD make a BIG difference! Once the package is within EU, there are no customs in between...

The good news: 2 tiny blue smt LEDs (which were the eyes of my Halloween costume) are still going strong (on 2 x CR016) after running continuously for 5 days! ooh... wrong experiment...  :-[

OK, start over
The Good News:

• I just finished my testing.
• The blu-ray is regulating fine - varying the input voltage from 8.5 - 11.15V, current/power stayed constant at 91mA/62mW.
• power was constant with ambient temp varying from 76-80 deg F. (62mW blu-ray; 118mW red)

The Bad News:
[olist] [*]my sensor head is a bit less sensitive at dead-center - can these things be damaged by a focused and overly-powerful beam? I get a more accurate (higher) reading with an unfocused beam - which may partially explain my lower readings here, because the beam is focused.
[*]there is a considerable amount of reflection from the sensing area - is that normal?
[*]we still don't know what Kenom's measuring difference is from.
[*]we still don't know why he could not get it above 75mW.
[/olist]
wrt #3 and #4 - since the driver appears to be regulating ok, there's really no need to mess with it. Other than curiosity, of course, and problem-solving for its own sake. Good thing there are no engineering-mentality people involved, so we  don't need to deal with the latter... [sub]:[/sub]

I still think though it would be good for Ken to re-check his measurements before they travel overseas. He'd need to really excercise great self-control though, to resist the temptation to open them up and 'fix' them  

As has been said many times before, the point here is to compare our meters and establish a standard. So for this first round, The Original Lasers are the LPF standard.

But subsequently, new LPF standard lasers may be created (for instance, when driver technology improves  [sub]:-?[/sub]) - all it would take then would be for a couple of the original testers to measure its output; and then we use their original-standard measurements in relation to our own, to calc a correction factor.
Unless, of course, anybody involved changed or recalibrated their meters in the interim[sub] ;-)[/sub]

Me, I'm going to wait until all results are in - and then I will make a decision as to which measurements I think best represent the 'true' values; and then adjust my meter to reflect that. Unless of course we can all come to a consensus on which value to accept.

hey, Gooey - you ready for your turn?

 
DanQ

danq said:

[olist] [*]my sensor head is a bit less sensitive at dead-center - can these things be damaged by a focused and overly-powerful beam? I get a more accurate (higher) reading with an unfocused beam - which may partially explain my lower readings here, because the beam is focused.
[/olist]

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Well, of course you are getting different readings when the beam is not focused, because rotating the lens in or out (or completelty removing the lens) changes the amount of light captured. When the lens is deep, a wider angle of light is captured, even though it still expands after the lens. If the lens is almost out, a smaller angle of light shines on the lens and light at a wider angle just shines at the inside of the lens nut. That's why we established the protocol that the lens should be glue fixed.

If the center of the meter is damaged (which can happen if the coating is exposed in excess of the allowed power stated in the data sheet, usually 10 or 20W/cm² on thermal sensors) then you just shine at a location off-center, if there is room

Zom-B said:

Well, of course you are getting different readings when the beam is not focused, because rotating the lens in or out (or completelty removing the lens) changes the amount of light captured. When the lens is deep, a wider angle of light is captured, even though it still expands after the lens. If the lens is almost out, a smaller angle of light shines on the lens and light at a wider angle just shines at the inside of the lens nut. That's why we established the protocol that the lens should be glue fixed.

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I think you misunderstood - or are mistakenly assuming a lack of understanding or subtlety of thought on my end that isn't there - or I failed to explain myself adequately to prevent such assumption.

To restate: there is a difference in readings taken with the focused beam hitting different locations on the sensor; and the reading is higher if the beam is not tightly focused but is sized to encompass a larger portion of the sensor.

Each of those conditions point to possible nonlinearity of the sensor in either local sensitivity or saturation response, or both. (there is little difference in the distance from lense to LD between a tight focus and enough un-focus for this to occur, so there is virtually no difference in the portion of beam entering the lense).

From that I conclude that for my meter it is more accurate to spread the beam somewhat; I mention the situation here so others with the same type of sensor might be aware of possible factors to consider.
  :-?
DanQ

I have a perfectly good thermal sensor and when I unfocus the lens enough to fill the region, the reading raises several mW

Yup I'm ready. But, I need to point out that I never put in my fair share of cash for this endeavor. Ever since the Boeing strike work has been slow so money has been very tight. While I would love to meter the lasers, it is ultimately up to all you who paid to decide if I should participate or not

GooeyGus, your on the list already... Have been, so how ever you got there, doesn't matter at this point! (IMO)

Jay

it's settled then...
the ayes have it!
;D
send me your address via email or pm, and I'll get it on its way tomorrow unless I'm unable.

DanQ

Zom-B said:

I have a perfectly good thermal sensor and when I unfocus the lens enough to fill the region, the reading raises several mW

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interesting - I wonder what the cause of that is... could it be simply that the broader beam, giving lower light intensity per unit area, results in less reflection? (presuming of course that reflections cause loss of enough light to matter)

Have you noticed, with a focused spot, any difference in response at different locations on your sensor? I'm wondering if mine is unique in that way; if so that may indicate that it was damaged in its previous life (my sensor is from one of the eBay used boards)

DanQ

doncha rechall gooey?  I paid your portion in trade for your prometheus!  Not to worry bud.  Gotcha taken care of.

How could you forget a friend getting your back like this! LMAO!!!

danq said:

[quote author=Zom-B link=1217029972/640#644 date=1226961496]I have a perfectly good thermal sensor and when I unfocus the lens enough to fill the region, the reading raises several mW

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interesting - I wonder what the cause of that is... could it be simply that the broader beam, giving lower light intensity per unit area, results in less reflection? (presuming of course that reflections cause loss of enough light to matter)
[/quote]
I already explained that part. When the lens is deeper, it captures more light, because light is still a cone shape when it leaves the laser diode. Also, reflections are not a nonlinear phenomenon. Recall your physics. %reflection = 100% - %absorption, and absorption is a constant for a given material. It can not suddenly absorb a greater or lesser ratio when lit more brightly.

Have you noticed, with a focused spot, any difference in response at different locations on your sensor? I'm wondering if mine is unique in that way; if so that may indicate that it was damaged in its previous life (my sensor is from one of the eBay used boards)

DanQ

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No

jayrob said:

GooeyGus, your on the list already... Have been, [highlight]so how ever you got there[/highlight], doesn't matter at this point! (IMO)

Jay

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;D


Anyway, glad to hear the driver is regulating! That was my one and only concern.

My apologies for not getting the test lasers sent on to GooeyGus until now, had a few bad days so just couldn't get to the post office. But it's on its way.  I'll try to get my data into the spreadsheet soon.

I didn't hear from Gooey yet re/address, but had one from a prior mailing - hope he hasn't moved! Signature required so if he's not home it isn't going to sit out over the holiday weekend.

DanQ

Hey Dan,
Sorry I forgot to PM the address!! But yes that is still my address and I'll be here to grab it! ;D

GooeyGus said:

Hey Dan,
    Sorry I forgot to PM the address!! But yes that is still my address and I'll be here to grab it! ;D

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that's a relief! I didn't think of the possibility of an address change until it was too late. Then even though it is insured, I was a little apprehensive.

You may get it Friday, unless they don't run any trucks on T-day; probably get to you by Saturday though.

DanQ

I got the laser and posted my results on the spreadsheet... who's next?