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

Thx ChicagoX, I'll try w/just two elbows. As an update, I've edited post #7 w/pics. For now, just as a POC for myself, I skipped the step down adapters and just placed the sensor at the lip of one end. I placed a piece of glass on the light end to hold the light in place. I noticed that I'm allowed some flexibility w/the placement of the light w/out affecting the reading drastically (the sensor however will read a bit higher once centered in the step down adapter).

Of course there's consideration to be given to the semi-glossy surface of the PVC so I may look to coat it w/IS paint.

Anyways more experimenting to come.

EDIT: Thx Langcjl, let's see... I mean, I don't mind criticisms as truth be told, I'm not even sure this would work but I don't think the forum should be disparaged on my behalf...

More i look at this the more I think a lux meter maybe in my near future. Maybe some pvc pipe as well. good work

I'm impressed with the out of the lightbox thinking involved here on your part .

I wasn't intentionally trying to dump on your idea .

The forum isn't going down the drain .it was a lame attempt at toilet humor .

Don't flush, I'm down in the basement still testing lights.

Thx Boaz! It's all good man, as I said, I don't mind criticisms levied at me/my ideas but just didn't think it would be fair to direct at the forum. Appreciate the clarification! :beer:

Are those LEDs in that toilet? Very appropriate.

wellchosenFoy

Sounds like a good idea to me. Something like a sink trap would completely exclude any direct light. But losses would be high. Would be good for the silly high powered stuff though.

Repeatability is far more important than absolute accuracy for what we're doing.

So here's the deal, I was afraid that this might favor throwers, and perhaps it does to a very light degree and as much as I remain a little skeptical myself, the readings keep telling me that I just might be on to something.

I took a few more measurements of most of my lights and they are all within % of claimed ANSI or mfg claims (and again using the same set up as above as I didn't have time to sand and paint yet).

I think these two test subjects are the clearest example that this might work:

This is the eGear Focus Control headlamp, it can be focused from flood (left pic) to spot (right pic) and in spot mode, it only increased the reading marginally:

This is a LumaPower XR-E R2 w/TurboForce Kit that casts a pencil beam sized hot spot (check my beamshots threads in my sig for beam profile) and if this contraption did favor throwers heavily, then this reading should be much higher but I think it's fairly relative for a XR-E reading:

L: Lux reading | M: stepped down to show beam profile | R: diffused light at other end

I don't have time right now to post the rest of the pics but the full album is here in case you want to take a look. I tried to include most of the light in the pic so you can identify them (EDIT: forgive the bag in the pic, it's acting as a ballast to hold down the pipe).

I'm sure the readings will be different once I sand down and mount the sensor in the center of the pipe but at least this seems encouraging no? More to come!

guardedlyoptimisticTim
(sorry Foy, I needed to just do this at least once during my time on this forum, but please know it's in your honor!) =o)

Tim -

LOL Very nice . . . and I thank you.

And, I also commend you - your pipe dream seems accurate. In fact, I'd like Match to chime in a bit more on this project. Specifically, does he think the light is sufficiently integrated? Your results thus far suggest that it may be. If it is, I'm thinking I would rather build this than a sphere.

needmorematchFoy

OK, so I actually haven't done any further fiddling with it and literally been using it as is w/out the adapter. Where it deviates from my original requirements is that it will be affected by ambient lighting so I need to take measurements in a pitch black room. While I don't have a baffle to deal with, thx to feedback from a member, I found out that ambient temp will affect the readings. So each time before I take readings, I'll first use a Xeno G10v2 (as Xeno uses ANSI values and it immediately runs nearly perfectly regulated on medium) to calibrate the sensor's position to match as close to 158lms as possible. Then I'll check the other levels to see if they're close to 480 and 10 on High and Low respectively.

The PVC (lms) column is what I've measured for each light. The output is measured in lux but wouldn't be far-fetched to call it lumens as the readings are pretty close for most of the lights. As expected in SureFire's case, they are known for underestimating their lumens and my readings corroborate that. Judging by the measurements, Sunwayman is also a little on the conservative side as well. All my measurements are done at 31seconds after turn on but of course it's not known at what time the manufacturers take their readings since it can be done anytime between 30secs - 2min.


As you'll see, it doesn't necessarily favor throwers. Case in point, the T40CS is near~47K lux and the V60C @ ~36K lux but yet the V60C registers 904 lux (lms) vs. 814 for the T40CS.

While I wish there was some engineering formula I could provide to calculate what is happening to the output after three pipe bends to produce these results but in a way it's been great not having to. I'm now able to consistently reproduce comparative WISIWIG (What I See Is What I Get) figures of how one light is faring vs. another.

The real nice surprise aside from the Sunwayman V60C were the ThruNite TN 10 & 11 as those readings were taken on only 1 x 18650 each, I'll post 2 x 18650 config (including step down) when I get around to them.

Anyways this has been a fun experiment for me and useful for comparitive purposes. Anyone else care to give this a spin? Assembly takes all of 5 seconds after you get the 3 x 90 deg. elbows.

TurboBB .. I still like this. waiting for the kit to be offered for sale winks. great job

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

_

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