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FrozenGate by Avery

DIY Thermal LPM for under $50

The HLPM II LPM Modules we sell are all calibrated in the
shop before shipping and output 1mV/1mW...
They attach to the DMM of your choice... we don't supply
the DMM we used for calibration..
The DMMs under $20.00 put side by side at 1000mV will
have have difference of ~+/- 1% (10mV)..

I just tested an expensive DMM against 2 cheap ones at
~1600 and got a difference from highest to lowest reading
of 6mV... that is only 0.6% total error or +/- 0.3% between
my 3 meters tested...

That would translate in an error of +/- 3 mW at 1000 mW..
(997mW to 1003mW).

Like I said... the problem of DMM accuracy is far from an
issue even with the cheap <$10 DMMs...


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
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Jerry I agree with you 100%.

All I'm saying is that the error, however small, (from any inaccuracy between the meters) is irrelevant if the same meter is used to calibrate it in the first place.

I may send mine to Mario to calibrate for me (I don't have any >100mW lasers that I'm sure of the Po), and if I do I'll send my VOM with it. He'll calibrate it to my meter and any possible that error of up to +-3mW will be avoided altogether.

All said and done I think that an accuracy of +-5mW from this set up would be very good. For simple hobbyist purposes, that is good enough. I used to own a LaserBee but unfortunately I had to sell it. Ever since I've missed not having a meter.

-Tony
 
Xplorer877 said:
Oh I see, yeah the specs were kinda misleading.



You're right there are many factors that will affect the accuracy of the meter but that is why the calibration is needed in the first place. There is no such thing as a material that will absorb 100% of the light. Otherwise you wouldn't even a reflected dot. But once calibrated the tolerances won't matter anymore. The accuracy of the meter doesn't matter as long as the same meter is always used. It'll be accurate relative to the Po because the system was calibrated to that particular meter.

-Tony
Click to expand...

Correct, because it is calibrated it is the componet repeatability that matters.
Get a laser of known power measured with a calibrated meter. Test/calibrate on the DIY meter with that laser.

FYI, Spectralon SRS-02 reflects only 2% of light from UV to near-IR. I've got some and it is BLACK.
It almost hurts your eyes to look at and focus on.
They also make SRS-99 which diffusely reflects 99% of UV --> near IR light.
It's so white it looks like it glows.
We use them (with other shades too) as Spectral Reflectance Standards for FTIR, Spectrophotometry, and Far-IR emissivity testing.

I'm not sure the SRS comes in paint form though... I'll have to call the company.
 
Where can you get some Spectralon SRS-02? As long as it doesn't burn it can be sprinkled over the wet paint on the TEC.

-Tony
 
This might be slightly OT... but not really.

Is there a way to make a cheap digital LCD readout that is driven by a mV detecting circuit? That way, we don't have to have to use a Multimeter. Not that a multimeter is a problem but I think it's be pretty slick if we could make the whole standalone unit... thermopile, amplifier, meter, and digital readout.

I've seen people make small standalone digital temperature readouts that plug directly into thermocouples... would a TEC be any different?
 
I thought about that too. The obvious solution would be to buy a cheap VOM and pull out the LCD and circuit. You can put everything in a nice project box and wire it up with a double pole switch. One pole will activate the amp circuit and the other can set the VOM to the mV range. I might do that. I have a small pocket sized Radio Shack meter that I don't use anymore since I got my Fluke meter.

-Tony
 
"Volt Panel Meter" ... yes that is it! Looks like digikey carries quite a few of them.
Thank you HIMNL! +1

OK guys, I ran around digikey a little bit and here's a pair f cheap 2V (2000mV) Volt Panel Meters.
Keep in mind, these run up to ~2000mV with good accuracy.
Instead of buying a DMM to use on an LPM you could use one of these... possibly even set drivers with it too.
A 9V battery can power these and I would reccomend a separate 3V circuit for the LPM. (1 9V & 2 AA/AAA)

CDPM312-ND ... Green Backlit Display, 2volt, 9v input ... ($31.19)
(Backlight requires a +5v input acheivable with a >500mW 5.1v zener diode and 1/2w 40ohm resistor)

811-1019-ND ... No Backlight, 2volt, 9v input ... ($30.14)

Here's one on Ebay ... Blue Blacklight Display, 2volt, 9V input ... ($8.99)
(It's not as accurate as the two above but 0.5% is OK for what we're doing)
 
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What you need is a 2volt self contained Volt Meter that
has a resolution of 1mV...
You can pick them up the cheapest on eBay... Why pay ~$30
plus shipping when you can get one for~$10.00 with shipping
included...:eek:

3 1/2 Red LED Digital Volt Panel Meter DC 2V on eBay.ca (item 390212706422 end time 23-Jul-10 07:06:11 EDT)

And yes the older Kenomerters and the nospin meter and my
own modified meters use similar meters..

BTW... the blue one posted above is a good choice as well and
even cheaper....
0.5% is more than enough accuracy... the rest of the $50.00 LPM
will be much more inaccurate than that...IMO


Jerry

You can contact us at any time on our Website: J.BAUER Electronics
 
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OK Hey just a quick update i order everything today except for the Box.

I decided to go with this Tec:
Digi-Key - 102-1672-ND (Manufacturer - CP60133)

I also Got this:
NEW 3½ Digital Blue LCD DC 0~1.999V Volt Panel Meter - eBay (item 280325833119 end time Jul-16-10 03:04:26 PDT)
Thanks Lazybeam;)

Oh and forgot to order some Alumina Thermal Adhesive and paint will do right now, So after these 2 i just need to get the box to put it in :)."Still Haven't decided"

Also i am trying to open Post #78 on page 4 and i cant because i guess i cant open a brd. Can someone that can open save it in a different format and upload here so i can open it. Thank You.:)
 
TTerbo said:
if your making this on PCB just use PCB design i posted.
super easy
Click to expand...

OK iam just going to do it on a breadboard for now..

This is my first time doing anything like this so iam learning as i go.

Can I use that same setup that you have on a Breadboard?
 
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