# Tool to Measure Light Brightness



## PocketLights.com (Sep 12, 2002)

Could anyone tell what kind of tools are out there to measure the brightness in lumens of a flashlight?


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## Doug S (Sep 12, 2002)

Brightness [intensity] is not measured in lumens. If you want to measure brightness [intensity] there are some inexpensive photometers around for $100 or so. A number of CPF members have LM631s I believe. If you really do want to measure lumens, you need an integrating sphere. Plan on spending $1000s.


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## shipinretech (Sep 12, 2002)

http://www.extech.com/WhatsNew/PDF_datasheet/Datasheets_English/401036.pdf
InReTech uses the Extech 401036 Datalogging Lightmeter with PC Interface. It cost us about $250 with shipping, and it was worth every penny. The only quibble I have is that it doesn't have an external power source option. Due to the endurance of our adapters, we have to stop testing after only 50 hours because the lightmeter 9V battery will die.


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## rlhess (Sep 12, 2002)

www.web-tronics.com has the LM631 Meterman lightmeter ($90ish) and a $50 PC-compatible Digital Multimeter (which came today). You can hook the two together and get a PC-logger.

Both Roy and Lambda are doing it.

Cheers,

Richard


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## Slick (Sep 12, 2002)

> Originally posted by shipinretech:
> *The only quibble I have is that it doesn't have an external power source option. Due to the endurance of our adapters, we have to stop testing after only 50 hours because the lightmeter 9V battery will die.*


<font size="2" face="Verdana, Arial">No sweat... You simply need to build your OWN external power supply. For example - new CD BoomBoxes don't have 12V cigarette lighter adapters anymore. I built my own out of piece of sprinkler pipe & a couple of endcaps to make a dummy battery pack. Round head screws & nuts make up the "battery posts" and are soldered onto a cig-socket extension cord... You get the picture.

Your conversion will be easy since all you have to do is go to Radio Shack and get a 9V battery hookup to get your conversion hooked up. You could then wire that to a 9V DC powersource that plugs directly into the wall.

One word of caution in doing this, is to pay close attention to the polarity when you use this connector because it will hook up the polarity opposite of what the red & black wires would normally indicate.

The simply solution is to check it w/your DVOM before plugging in that precious light meter...

..Then you go buy better beer with the $ you save on all those 9V batteries that you're not using any more






Now go bring us the FULL runtime stats on those adaptors.





BTW - are your red-orange AA adaptors Luxeon's? If so, is that price right?


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## [email protected] (Sep 13, 2002)

> Originally posted by shipinretech:
> *The only quibble I have is that it doesn't have an external power source option. Due to the endurance of our adapters, we have to stop testing after only 50 hours because the lightmeter 9V battery will die.*


<font size="2" face="Verdana, Arial">In addition to Slick's comments...How about just putting a couple of 9V batts parallel?

(of course the 'buy more beers' option is better...)


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## e=mc² (Sep 13, 2002)

Hey, check this one out. If you already have a PC capable DVM like the one Roy and I now have, you can always buy one of these $60 adaptors by Extech:

DVM Light Adaptor 

Notice one model is for LUX and the other model is for Foot-Candles. Too bad they can't have both units of measure on one unit, but for $60, hey.

e-


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## INRETECH (Sep 13, 2002)

Yes, we are going to replace the battery with an external power source to allow longer than 50hrs of testing


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## shipinretech (Sep 13, 2002)

Then the problem will be "When do we stop testing?" 

I said it was a quibble, and it was more about the design choices that Extech made. One of the application choices they designed for was clean room operation, and more holes in the unit probably gave them more potential locations contaminants could cling to.


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