Lumens measuring contraption... (or just a pipe dream?)

I put the PVC LMD into action with my latest review:
http://www.youtube.com/embed/VR1Aeqe1A24

With this, I am now able to provide real time lumens measurements with my runtime testing so that for non-regulated lights, it allows one to get an true idea of real expected output for the duration of the run.

Cheers,
Tim

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Thx guys!!

@moT & RC - this is why I LOVE this forum. Classic replies!

I use a $75 dollar DS0201 pocket oscilloscope for my measurements.

Hi rennsman, welcome to BLF!

You're using an oscilloscope to measure lumens? If so, would you mind sharing how that works?

To the best of my understanding, that's mainly useful for detecting PWM but if it can be engineered to measure lumens, I'd love to know how.

Thx!

No, it's only for measuring PWM, just thought I'd mention it due to your plan's mentioned in the OP.

Hi rennsman, sorry for late reply, my alerts keep randomly getting changed for some reason I didn't notice your reply 'til just now. That looks to be a very interesting oscilloscope.

Just two q's for you:

1. Would you happen to have any samples of graphs output from it

2. Is it enough to cover the entire frequency one might expect to be generated from flashlights using PWM?

Thx!,
Tim

Reviving old thread (in process of restoring pics). Wanted to get feedback from those using this setup:

  1. How well has this worked (not interested in "accuracy" per se but rather repeatable consistency)
  2. Is your set up "set and forget" or can you calibrate (please share methods for calibration)
  3. What changes have you implemented?
  4. What is your reference light and have you been able to use a known calibrated light for comparative measurement.

Thx!,
Tim

Hi Tim. I notice you did not use the reducers. Are you shining the light through a piece of perspex with a hole cut in it and is the sensor just positioned in the open end of the tube? Thanks.

Correct, I decided not to use the reducers as I found given the temp swings in my room, I have to constantly calibrate ahead of each measurement so I use clamps to hold the sensor. The lights rest on a sheet of glass with paper templates so as not to give large bezel lights an advantage (since more light is reflected back in).

You can see it in action here (not sure if it'll keep the specified time but if not, jump to 25:58):

The black cloth on the sensor side is to block it from measuring ambient light (and the giant C-clamp is just a weight ballast, never did get to bolting this down to a base... )

1 Thank

Thanks.

I’ve been using the PVC trap box for a while now and really enjoy having repeatable results to go by in building lights. Seeing results from the build makes it so much more fun and interesting. I’ve gotten criticism as I seem to manage to build lights that are over the top, but I believe it’s due to some of my tricks eliminating resistance as well as accurate amperage measurements.

manxbuggy1 and rdrfronty built my box for me. They have one that was calibrated with a LOT of lights! They used their base lights to calibrate mine and I’ve built lights for both of them that are tested in my box before leaving here and again in their box and we are getting very close readings, consistently.

We use a foam surround to block out ambient light, with 3 main opening diameters that fit almost all lights. The meter end is closed with a hole cut for the meter and a velcro strap holds it in place. Easy repeatable results. My box has a multiplier of .345, Tom E uses .350 I think, and Richard also has one, not sure of his multiplier.

The interior is painted white, the glass shelf is glued in with clear silicone. Love it!

The light sit on the glass shelf?

Thx for the feedback Dale! How do you feel temp impacts the readings?

I had previously measured RDR's O-Light SR90 and was in the same ballpark so it's certainly consistent. I'd like to get a few different lights calibrated at different outputs though since my Extech HD450's reading deviates by about 7% or so when jumping between the 400 to 4K range (does that apply to you as well?).

@MRsDNF - yup, sits right on top of the glass and I usually have a USB fan on lowest setting blowing on the head during max output runtime testing.

Yes, the light sits on the glass shelf and the foam centers it and blocks outside light. I need to make a brace for the curved piece under the light, some of the big lights make you hold it or prop it with something.

The Olight SR-90 Intimidator is one of those! Measuring some 1600 lumens in the box with the de-domed XM-L2 U2 1A it does 610Kcd on the meter at 5M. I’ve seen it hit 622 before with fresh cells, but the proprietary battery pack is getting old and I only have a car charger to charge it with. Need to rebuild it…

rdrfronty had me rebuild his Olight SR-90, then he gave it to me! It’s a prized possession to be certain!

Daggum…that is alot of data! awesomeness!

There are flashlight hobbiest…then there are you guys :stuck_out_tongue:
(I still say photon phreaks is applicable here) :smiley:

Keep up the great work!

I have pretty much the same setup, with 3 90 degree fittings & an end-cap with hole cut to attach the sensor head.

Can you elaborate a little on the equation you are using to get your final lumen numbers?

Ie; setting/range used on the meter * multiplier , etc.

Cheers :beer: