Power Meter Calibration and Comparison

I'm still in, just waiting for my 'play money' to come in tomorrow so I can pay

I think I'm going to hold off a day or so, to get my second meter before shipping this off. I know that we're all anxious to get our hands on these and start testing but in my opinion, it would be better to make sure it's spot on before shipping this bad boy out.

Uhh zom-b, no offense but I'm curious what your independant tests have to do with this test?? I know that the tests your doing are related but do they really have a bearing on the lasers that are going to be passed around? Are you using it as a basis for testing methods? I'm not trying to discourage you or shoot you down. just if it's relevant how so, if not, then you can keep posting the data, but it might be out of place on the spreadsheet. Just curious.

I made those test measurements to see if the spreadsheet works in it's current shape. I found that it was inefficient to have both red and violet ratings on one row, as conditions might differ between those measurements. I changed it to have one measurement per row, and as such, I changed the columns to one that holds the color and one that holds the measurement. I see that you changed it back. Are you sure two measurements per row is doable?

I also added a column for temperature, as it is far more important than have it as a part of the conditions column.


[edit]

Kenom said:

I'm going to set the focus around 1mm-2mm on each of these at 6" then glue the lenses down.

Click to expand...

I hope you have focused the lasers at infinity. If the beams are collimated, there is a chance that people will accidentally locally overload and destroy their sensor, while in the process of placing the laser 6" from the sensor.

Updated version of the instructions:

Repeat this entire procedure for every meter in your possession.

Global precautions and preparations:
1. Check if the dust cap was on when receiving the laser. If it was not on, try to guess how much dust has collected. If unsure, report to the forum for further instructions (macro-photo recommended).
2. Check if the focus ring and body are still fixed. If unsure, report to the forum for further instructions (macro-photo recommended).
Reserve 3 (6?) rows in the spreadsheet with in each row all information that you can accumulate at this time.

Environmental Precautions:
1. Work at night or in a space completely shut off from sunlight.
2. If the power meter has a warm-up time, turn it on now.
3. Get the temperature as close to 25C/77F as possible. (wait for night or use airco)
4. Stop air currents (Close the windows and doors and/or shut off airco)
5. Be the only one in the room to prevent body heat from others to pollute the measurements.
6. Be in the same location every time a measure is performed (changing position might pollute the measurements)
7. If possible, aim the sensor aperture away from you, not facing a shiny surface (eg computer screen), while still having access to the zeroing knob and the readout.
8. Place or mount the sensor on a stable surface or vise, to eliminate the sensor moving relative to the laser.

Preparations phase:
1. Mount the laser and the supplied clamp and tripod.
2. Connect the cord to the adapter, check if the adapter is off, and plug in the adapter
3. Place the laser aperture 152mm (6 inch) from the sensor's active surface. Try to minimize laser runtime while doing this.
4. Turn on the power meter (if not already on) and select the lowest range that will not overflow from 150mW.

Measurement phase:
1. Zero the meter. Take the time to let it stablize. I mean, really take the time. It is better to spend three times as long at zeroing it well, than three times zeroing it less well.
Repeat three times:
2. Turn the laser on for 30 seconds. Remember the average reading within the last 5 seconds.
3. Check the zeroing. If it changed more than 4 digits in the rightmost figure, discard all readings and restart from 'Measurement phase'.
4. Measure the current room temperature, for the record. Record the reading and temperature in the spreadsheet.

Finishing up phase:
1. Return the dust cap.
2. (Optional) If you have made your own stable "temperature-correction" reference lasers, use the reference laser with the same color as the calibration laser, and measure it's output three times, as done in the 'Measurement phase'. The average of these three measures is your reference value.
3. If the calibration laser was red, repeat from 'Environmental Precautions' with the violet laser.
4. Turn off your meter.

Optional step:

Recalibrating your meter:
1. Calculate the correction ratio as {actual power of red calibration laser}/{average reading of red measures}
2. Find or build a laser that has a power just below the maximum power of the currently selected range. (For example, a laser of 250mW with the 2000mW range is less accurate than 180mW with the 200mW range). Remember to build a laser that is at least a factor equal to the ratio, lower than the maximum reading
3. Mount it for stability and aim it at your meter
4. Zero the meter
5. Let it warm up and stabilize as long as necessary.
6. turn off the laser, Check the meter zeroing, and turn the laser back on.
7. Read the power
8. Multiply the power with the previously calculated ratio. This should be the actual reading of your laser,
9. Adjust the pot on your meter such that the reading equals the calculated value.
10. Turn the laser off. Check the zeroing again. If it was off, then repeat from step 6
11. Calculate your correction ratio for violet as: {red ratio}*{average reading of violet measures}/{actual power of violet calibration laser}

Well, I think it's important to keep the reading seperate and there's plenty of room to indicate multiple readings not just one. However it would be very simple to do what you had done and indicate each individual reading per row.

I knew there was a reason for your postings and I appreciate your contribution. Thanks for letting me know. I like what you've got for testing procedures and will do so with my own testings.

As far as the focus is concerned it's not near focused enough at that distance or close to it, to have to worry about it coming to complete focus while getting it setup. I didn't set it to infinity because both when set to infinity have a really large diameter beam and for meters with small sensors, it's going to be hard to get all the light on the sensor.

I don't know if the shipping order has been determined yet, but Scopeguy asked me to mention, he will be back on the 16th.

Originally he asked to be last on the list, as he thought he would not be back in time, but now he can still get in row for the calibration laser before it leaves for EU...

Thanks Igor! My internet here is very unreliable, but Big Bear Lake is lots of fun! AMB! -Glenn

I am back home, (as of Aug 16th), so, any order you guys decide on is fine with me.

I couldn't resist and purchased a new meter. So, I'll be putting up my scientech for sale. I just have to brag... check it out
http://tinyurl.com/5rc8hh

Kenom said:

I couldn't resist and purchased a new meter. So, I'll be putting up my scientech for sale. I just have to brag... check it out
http://tinyurl.com/5rc8hh

Click to expand...

Niiiice!

Have you found a calorimeter for it yet?

Peace,
dave

Well, I'm hoping I can rig one of my sensors for analog, and save up to buy a brand new one with the calibration heater attached.

daguin said:

[quote author=Kenom link=1217029972/360#375 date=1218839355]I couldn't resist and purchased a new meter.  So, I'll be putting up my scientech for sale.  I just have to brag...  check it out
http://tinyurl.com/5rc8hh

Click to expand...

Niiiice!

Have you found a calorimeter for it yet?

Peace,
dave[/quote]


Hey I have one too, that makes three. This is such a new model it will be hard to find a used calorimeter for it and a new one is too costly.


Kenom, nice you got a great deal.

Yeah, I've got a price sheet for the sensors new. They are MINIMUM $800. That's the cheapest. $795 Now that's not including the sensor automatic calibration heater. time to stop smoking.

I have been searching for the last 3 to 4 months now but nothing used.  I can't justify spending that type of money for a hobby right now.   :'(

Kenom said:

I couldn't resist and purchased a new meter.  So, I'll be putting up my scientech for sale.  I just have to brag...  check it out
http://tinyurl.com/5rc8hh

Click to expand...

Man! What a deal you got on that Kenom!

I just paid $499 for my E-bay Coherent PowerMax 5200. Well, mine includes a Coherent PM3 sensor though... It's on it's way to me now. Just in time!
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=180275358541&ssPageName=STRK:MEWN:IT&ih=008
Jay

I always knew I had a Coherent sensor, but I just found out the type of my sensor: P10-19C [edit] PM10-19C [/edit]. It was hard to find as I did not know the specs and it even seems it's an old part. Now I also know what that strange canal is I saw, water cooling . It also seems the 10mm messing plate I have on the back is not standard, but some kind of temperature sensor/heatsink option. I couldn't find those on Coherent. It also seems someone must have opened it and placed a plug on the body, as from what I can see, the original ones have a fixed cord.

Your thermopile looks the same as the one i have in my meter.. Did you get yours on the Coherent board from e-bay?
Mine even has the same scratch in the same spot.. Mine also has the BNC connector and the heater plate on the back. I didn't see any water cooling canal tho..

What kind of amplifier are you using? I have a single op-amp circuit at the moment, but i am replacing it with a three op-amp circuit before the calibration, so that the gain won't be affected by the offset anymore. It's not much, but it will be a little bit better.


I also made a reference laser with a weaker diode, that i can't use for much else (only 60mW at 100mA). This one is stable in power, but i have found another one, that actually climbs with heat! Starts out at 155mW and goes to 165mW. Maybe yours is like that too. Don't remember seeing this in the previous batch tho. My 6x drops a few mW with heat.

I hope i can get the constant temp. pletier driver finished in time for the calibration...