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Measure mW without a meter?

lamborgini8

lamborgini8

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I heard some time ago you can measure the current and you can work out how much mW your laser is giving or something.

I don't have a meter to test it and they are stupendously expensive for something I will only use once or twice every few months so how exactly can I measure the mW without one?

I will be having my red open can running at 300mA (once its finally finished that is), how much power would that be putting out?
 





B

BluRay

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you can pick up a cheap multimeter anywhere. you dont need the best ones. just some cheap china brand ones. In Oz they sell them for $5 onwards.
You might not use it much, but when you need it, it would be handy to have it ;D




Tommy
 
lamborgini8

lamborgini8

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BluRay said:
you can pick up a cheap multimeter anywhere. you dont need the best ones. just some cheap china brand ones. In Oz they sell them for $5 onwards.
You might not use it much, but when you need it, it would be handy to have it  ;D




Tommy
Click to expand...

I have seen cheap ones about but they only measure up to something like 150mW which I am expecting more...
 
lamborgini8

lamborgini8

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I think we all got a little confused here.

It's not a multimeter I need, its a laser power meter.
 
B

BluRay

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Oh, well thats different. LOL

Another suggestion would be if you really want to test it, is to have a trusted member with a power meter check it out for you and send you the laser back.



Tommy
 
Bionic-Badger

Bionic-Badger

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Not accurately... but you could measure the input mA, and compare against the various graphs that have been made for the different diode types. It won't be super accurate, but will give you a ballpark figure.

Otherwise, you really can't without spending decent money. There are photodiodes and photovoltaic panels, but they have to be calibrated, and if you can get them calibrated, you'd probably have access to a meter anyway.
 
Tw15t3r

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I think.... this could be possible, although most likely very inaccurate.

Measure max mW output possible:
1. Voltage of diode x current used
2. multiply by 50% (I assume that no diode's more than 50% efficient?)

Measure min mW possible:
1. 100ml of water
2. throw in a piece of black paper
3. shine laser into the water on to the black paper for 30secs
4. measure temperature rise in water
5. power = 4.18 x 0.1 x (temp rise) / 30

That should give the margin i suppose.
 
electron

electron

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John_Lawson,
Did you have any luck with it? I have one of those too and it's not even worth the postage let alone the time to ship it back.

If the OP simply wants to know if the laser is putting out decent power, just try and burn some matches, your skin, or pop some balloons.

You could also get a thermopile and hook it up to a dmm and that would work cheaply too. Otherwise you might just want to ask someone to measure it for you.
 
lasersbee

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Hey electron...
I've already mentioned and will repeat... if you or anyone here on
the forum has one of the first versions of the LPM Module (it is only 30mW rated)
that has the metal encased Sensor... Just send it back to us and we will replace it
FREE with the newest (non metallic encased) Version that is rated at 120mW.

You or anyone are invited to PM me for our Address.

Jerry
 
electron

electron

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That's cool, I'd have to go back and dig it up; bought it, tried it; dumped it into the useless pile somewhere.

Hey would that be transferable? as I won't mind giving it to someone that can use it, so could they then trade it in?

I've got too many meters now I'm no longer using.
 
lasersbee

lasersbee

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electron said:
That's cool, I'd have to go back and dig it up; bought it, tried it; dumped it into the useless pile somewhere.

Hey would that be transferable? as I won't mind giving it to someone that can use it, so could they then trade it in?

I've got too many meters now I'm no longer using.
Click to expand...


Sorry... the original owner must send it back for the FREE replacement.
And it must be in undamaged working condition....

You can always give it to someone after wards.
 
electron

electron

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OK then, anybody want to pay the shipping on this and what ever else may/may not be required?
I would guess since I really have no other info on this, you'll have to pay shipping to Canada and maybe return shipping back to the States? IF anybody wants to do this, the unit is yours Gratis; you pay whatever shipping/terms he wants, when the replacement unit arrives back to me, provided your located in the CON USA, I'll ship it back out to you un-opened; Gratis. PM if interested.
 
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