home made laser power meter

[badger1666]

i got bored and found a little project on lpf started by mario master.
diy power meter for <$50, i thought it wont hurt to give it ago
so i made up the small amp and used a 15mm tec glued to an old cpu heatsink
picked up a small 0-1999mv panel meter off ebay, small plastic box from maplin
and away i went ,and a few hours later a power meter was born,
and was suprised at how well it works just need a laser of a known power to calibrate it
its a little slow reading power and going back to 0 again but thats proberly down to me using a 15mm tec, it works quicker with 8mm tec but i had knocked one of the wires off mine so i used a tec that came with my die4chill.
it makes a great little hobby meter for just tweeking up multi diodes setups
does not really matter if its super accurate or not,but its better than no meter at all
but its good for upto 2watts

[LaNeK779]

brilliant!

so,if i get this correctly, the beam heats the tec and then you amplify and measure the voltage that the tec generates?

[MarioMaster]

This is the principal behind the Laserbee and my new series of power meters at Radiant Electronics.

Glad the circuit is useful to you

[planters]

If looking for a relative PM for aligning an IR laser of about 1W could you simply use a mV meter and a TEC? What kind of voltages are you talking about and the response time for a given power range (you pick) with that TEC?
Thanks

[mixedgas]

If looking for a relative PM for aligning an IR laser of about 1W could you simply use a mV meter and a TEC? What kind of voltages are you talking about and the response time for a given power range (you pick) with that TEC?
Thanks

There is a bit of thought that has to go into how the heatsink behind the TE is set up, and the number of TC pairs in the TC. Most thermal heads made by companies that do this for a living have a cal heater in them and a anticipator circuit in the meter read out that speeds up stabilization of the meter reading and reduces overshoot.. Pro heads are often .1 mV per watt or 1 mV per watt. There is a attenuator circuit on the back side of the TEC that is fatory set for interchangability on a pro unit. On a pro unit the adsorber is sputtered on, as well.

But yes, the home made ones work fine over a limited range.


Steve

[mixedgas]

TEC, 50K potentiometer, 0-200 mV meter readout. The rest depends on the TEC and the number of couples in the tec. more is better, to a point.

Steve

[planters]

After describing the application to the tech at Custom Thermoelectric his recommendation follows your suggestion. And so I selected a 37x37mm high V low current TEC with 198 thermocouples (a lot) and with a 1Kg Al heat sink thermal greased to the back and their graphite based thermal absorber on the front I am going to try this with my Fluke D. PM ( resolution, 100uV).

I'm going to solve this damn conundrum!

[steve-o]

I built one of those a while back, spray-painted the tec front with krylon flat black and have had good luck with it. 2 watts of 445 wont even burn it. I used a datel 0-2000mV LCD meter. Not quite as pretty as the LED meters, but easier on the battery. Also just needs one 9V batt; no split power supply, no external circuitry.

[lasersbee]

I built one of those a while back, spray-painted the tec front with krylon flat black and have had good luck with it. 2 watts of 445 wont even burn it. I used a datel 0-2000mV LCD meter. Not quite as pretty as the LED meters, but easier on the battery. Also just needs one 9V batt; no split power supply, no external circuitry.

You could probably go higher in power by simply defocusing your Laser's
beam and covering more of the active area of your sensor..


Jerry

[planters]

I am amazed! Like the engineer at the TEC supplier said, these things are incredibly sensitive. With a voltmeter capable of 100uV resolution these will respond to the IR radiation from a single finger placed 60mmm away from the front surface. Really! I now see how a micro-bolometer imagining array could actually work. Of course this would be a pretty big pixel!

Between 0.5 and 1W on the front surface and 100 to 200 mV output. Obviously, not calibrated and probably not precisely linear, but because it measures heat flow the slow temp rise ( 1-2C) of the heat sink as it sits on the optical table makes no noticeable difference and so this meter is very stable. With its precision, rapid response and stability, I actually like it better than my expensive Ophir meter for PO during alignment.