Light meter getting wildly inaccurate readings - did TomE's Super TN31 break it? - SOLVED

LED Flashlights – General Info
1

Quick update before I go out:

I just picked up my TN31 modded courtesy of TomE from the mailman. The box is surprisingly small. I chucked some NCR18650A (2900) cells in all at 4.20 volts, put another 3 4.20 volt cells in my BTU Shocker. Time to test out the new beast, right?

Well here is where it gets weird.
TomE measured it at 349kcd. I can not for the life of me replicate that number or anything close to it. But consistently, the TN31 gets 3.3x that of the reading my BTU Shocker gets (AR coated glass, 3.8A regulated driver).
From my measurements I’ve made readings of around 130kcd for the BTU Shocker. 130*3.3 = 380kcd. This is the closest I’ve gotten to TomE’s reading.

Anyway so I tried to work it out from 5 meters. At 5 meters I got 11059 lux, (5^2)*11059 is the formula right? Because that gives me 276kcd. But then if I were to go by this, that would mean my BTU Shocker is at 84kcd which I’m POSITIVE is not the case.

So anyway, I’m in need of a new light meter. Any recommendations?

2

I’m not sure what you are trying to say actually, but your math is wrong: 130*3.3 = 429 Maybe thats the problem?

3

Oh right, yes sorry my math was wrong. But my point is that it works out to be way higher than it should be.

Relative to the BTU its 429k
Calculated by reading itself its 276k

When I get home I’ll measure it again. This is seriously doing my head in.

4

Slewflash, perhaps you can use your Nexus 4 to confirm your readings a little further from the sensor.

I think at 10m you should read 3490lux, according to TomE?

5

Haha true Ryan! I’ll try that when I get home and hopefully solve this problem.

6

Great, let us know how this works out! :slight_smile:

7

Hm, I got roughly 3100 (I don’t know how to read exact values on Physics Toolbox Light) @ 10 meters.
Not sure how accurate that is, but that translates to 310kcd.

I’m going to guess that my Nexus 4 is reading a little low, for the Shocker @ 10m I got just above 900, which is just over 90kcd - this is NOT typical of what a BTU should read.

I’m just going to get another light meter… Not sure what happened to my light meter but suddenly it reads crap. I measured at 10 meters for the BTU and got a wacky score of 84kcd. Although it is quite close to what the Nexus 4 read it is not credible as the N4 reading is not consistent with the light meter.
I WILL to get to the bottom of this!

… So any recommendations for a light meter?

Ryan: Does your N4 also read low on some of your lights? Or does yours give readings consistent with other reported numbers?

8

Unfortunately, I don’t have any stock lights that I can use as a reference.

All my lights are tweaked, but I’ll let you know how accurate it is if I get a light meter as well. :slight_smile:

9

It still is a beast, over 1100 lumens on high and shoots over a kilometer. Love the mode spacing too.
With my new light I can now disturb more neighbours than was ever possible!

10

Crazy question, did you try a new battery in the light meter?

11

Hm… I’ll give that a shot and see what happens.

12

Holy crap. FMcamaro that was GENIUS. Why did I not think of that. I'm hitting myself now that I almost bought a new light meter.

Anyway thanks to FMcamaro I can now retest both these lights.

The reading was the same at 5 meters and 10 meters ± 30 lux.

At 30 seconds:

TomE's Super TN31: 370,000cd

BTU Shocker w/ AR coated lens: 133,000cd

I am VERY pleased to see this number. I would agree that TomE's light meter reads a tad low, and mine a tad high. To estimate, I would say it's closer to 365kcd. This far surpasses the 250kcd needed to become a kilometer light. This sits nicely at 1,208 meters, 1321 yards or 3963 feet. Now to get a mile light (1.6km) I need to reach 647kcd. Hm, Maybe when the XPG3 comes out.

Relative to the BTU Shocker though, which I estimated conservatively at 2700 lumens, the ceiling bounce gives me 1441 lumens from the TN31. This is seriously bad ass, and in the 4°C (39°F) I can really feel the neck warming up really fast which is good! This will DEFINITELY help with fishing. I feel so excited. This is such a great light. TomE and XM-L2s really are amazing :)



13

Woot, great job you two!

Batteries are the culprit of wonky measurements, from DMM’s to lux meters.

Can’t believe we have been scratching our heads because of that! :stuck_out_tongue:

So the Nexus is reading a little low?

14

Is TomE’s TN31 a OSTS modded one or did he mod it himself from stock? Either way I’m keen to get one!

15

Yeah, looks like it reads way lower than it should, not sure if it’s my Nexus itself, or they all read low - still good to get a ballpark range though, just up it by about 19-20%. But my light meter I suspect also reads a little high, just a little.

He modded it himself from a stock XML2 TN31, it has a resistor mod (5.6A) and dedomed the stock emitter. OSTS uses an XPG2 and has I think closer to 650 lumens, and 400-440kcd.

16

Thanks for that info. I wonder if this is consistent through out all the Nexus 4’s. :slight_smile:

TomE’s is much more practical I believe. :slight_smile:
Is the stock PCB better than SinkPads?

17

Apparently so - it’s thicker than the SinkPad which is why he chose to use it over the SinkPad.

18

Nice, thanks for your reply.

19

Ahh ok, so the OSTS has a pencil thin beam, where TomE’s is a thicker beam that doesn’t throw as far as the OSTS TN31? Is that right?

20

That would be correct, but keep in mine that the XML2 version (TomE’s version) has 2x the lumens and still illuminates things 1.217 kilometers away (to 0.25 lux, 600 meters to 1 lux). Think about how far 1.2 kilometers is. For what it’s worth, 440kcd (the absolute highest that it will be, 400k being the lowest) throws a beam 1.327 kilometers away (to 0.25 lux).
The XML2 would have a much larger hotspot thus making it more useful for spotting things. Personally I’m using it for fishing so I went for the XML2 route, as following fish with a pencil beam isn’t exactly easy (I tried with a Jacob A60).

Maybe if I was using it for signalling or shooting balls of fire then I’d consider getting the OSTS.