I just bought the Extech model 401021 light meter that hooks up to your multimeter. The manual is onlly 2 small pages and dosen't gives very little info.. I have a Radio Shack model 22-163 digital multimeter and a Sperry DSA-400 volt meter and amp meter.How far do you put the light from the sensor ?.Any information would be helpful. It will be used for personal info. for my lights only and dosen't need to be too acurate. In other words how does this thing work?. Thanks for any help or websites that would help.The Extech website only had the manual download. I can contact the company by phone ,but figured I would probably get more useful information here.
Extech 401021 Light Meter Help Needed
- Thread starter CaptainD
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SilverFox
Flashaholic
Hello CaptainD,
Common light readings for flashlights are given in foot candles and Lux. Foot candles can be taken at 1 foot and reported as such, or given that light falls off with the square of distance, you can take your measurement at whatever distance you want to, then you can do the math and normalize your reading for 1 foot.
The same goes for the Lux measurements. With medium power lights, you can usually use the 1 meter distance and get good results. With very dim lights, you may have to move closer, and some lights have a reflector, or lens, that shapes the beam of light. When measuring these more powerful lights, you need to pick a distance where the beam is fully formed.
5 meters usually works for most of these lights, but there are some specialty HID lights that require greater distances. You can "play" around and the inverse square law figure out about where you need to be.
Here is a beginning handbook on measuring light to get you started...
Tom
Common light readings for flashlights are given in foot candles and Lux. Foot candles can be taken at 1 foot and reported as such, or given that light falls off with the square of distance, you can take your measurement at whatever distance you want to, then you can do the math and normalize your reading for 1 foot.
The same goes for the Lux measurements. With medium power lights, you can usually use the 1 meter distance and get good results. With very dim lights, you may have to move closer, and some lights have a reflector, or lens, that shapes the beam of light. When measuring these more powerful lights, you need to pick a distance where the beam is fully formed.
5 meters usually works for most of these lights, but there are some specialty HID lights that require greater distances. You can "play" around and the inverse square law figure out about where you need to be.
Here is a beginning handbook on measuring light to get you started...
Tom
Thanks Silver Fox. It will probably take me a while to absorb all that was on the link you provided.I did find out part of the very small owners manual with the meter was left out.There was another section that gave more info. on setting it up. Maybe I should of gotten one of the Meterman meters to begin with.I'll play with the Extech awhile.I have already learned there are many things that can affect the readings. Thanks again for your help. David
