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

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

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.