Am I using my light meter correctly?

just got it today, and it is quite exciting to be able to do my own measurements.

it is a cheapie meter, but my intention is more for comparison, than overall accuracy.

it has a dial which goes through the ranges: off--200--2000--20000--50000. it can read both lux and foot-candles.

i placed the meter in a very dark area (basement), the sensor mounted on the wall. then i set up a vice to hold the lights. i took the measurements with the lens of the lights at 1 meter from the sensor. i allowed the flashlight to run for ~5 minutes before taking a reading, as i noticed the reading would drift down a bit (is there a surface charge on the battery which is relieved in the first few minutes?), and then stabilize. i placed the center of the beam on the sensor.

the sensor was set on "200 lux", except for 2 of my samples, which required changing to "2000 lux".

my results are a bit surprising, and perhaps inaccurate:

CMG infinity ultra-------21 lux.

PT impact II------------110

PT Attitude--------------51

PT Aurora----------------32

Franken-beam------------478

PT-40-------------------745

the Ultra was on lithium. the rest on alkies.

the aurora has roughly 12 hours of use--on low beam for reading at night.

"Franken-beam" is my first mod: twin LS/O 1w mounted in a 3-d $ag lite, direct drive with 3-d cells! there is over 2 hours on the batteries (i ran it for 2 hours straight to test the heatsink). i need to post some beamshots of this thing--it is so much fun!

the rest have less than 1 hour on them.

later,
Bob

Bob,
Yes, the battery voltage drifts downwards and also, in the case of the LED lights, they become less efficient as the LEDs heat up.

thanks for the comments--this has become a very steep learning curve for me.

there is a LOT of knowledge here!

hopefully i will be able to post my mod soon--but honestly, i have been reluctant.
it is nice, but not nearly as exciting as electrolumens' stuff.

what is fun about it is the facial experssion of people that see the incredible amount and QUALITY of light it produces. it is like a flouro with throw. no rings or irregularity.

i fire it up in a dark room, and the whole place is lit up evenly, like someone just opened the blinds on a bright morning. the look on my fiance's face was priceless!

now she wants one in a smaller package, so i think i will do the same with a 2d mag and 3 c cells.

what is interesting is that i noticed in testing that there was quite a big difference in brightness going from 1 to 2 LS, which made it well worth the effort to build it with 2.

Bob

i forgot to mention that i replaced the halogen bulb from the PT 40 with a rayovac kpr113 krypton, because the original beam was poor.

this probably resulted in less lux, (i dont see a difference), but the beam is slightly broader and much smoother.

and the bulb should last well.

Bob

Originally posted by pedalinbob:
thanks for the comments--this has become a very steep learning curve for me.

what is interesting is that i noticed in testing that there was quite a big difference in brightness going from 1 to 2 LS, which made it well worth the effort to build it with 2.

Bob

Click to expand...

<font size="2" face="Verdana, Arial">Bob, well you are learning fast! There is a lot of merit to using multiple luxeons instead of just driving one harder.