Is it common to hit a run of bad luck?

I chose 61A simply because it is the cheapest of the 61 series and has all the functions I need.

@ Vectrex: Thanks for that. So basically a cheapo MM is safely accurate for voltage readings when charging L-ions, but no good for, say, tailcap measurements (not that I have the first clue what they are, what they signify or how to do them)..

You know, I honestly think someone should suggest a tutorial or library sub-forum for BLF. It's such a great forum, and there's so much knowledge and info within these archives, but it's so scattered and buried. The search engine is very good, but type in any Q containing the words "Tailcap Reading" and you get over 100 hits, and none that I've found so far explain or take you through it. There are so many clever guys here, BLF could become the best flashlight learning facility on the planet.

true, Lensman. i will have that DMM and not know how to do tailcap readings properly. Especially with small lights (AAA keychain lights, ..) i wouldnt know how to do it. Once everything is connected i could do tailcap readings (amperage) over the capacity lifetime of the battery.. but a Ampere-Time-graph isnt very helpful since it's not the current which is stabilized but the brightness (brightness ~ power (watts) = amperage x voltage). When voltage drops, amperage will raise quite a bit in order to maintain constant LED power.

Without proper tutorials how would we know ..etc.. ?

It "can" be accurate and it's less of an issue compared to current readings. HKJ who is also a member here has made a nice DMM tutorial over at CPF and our very own flashlight wiki by brted is also a great start to get a hang on the most basic terms.

There is one EXCELLENT tutorial done by HKJ here on BLF and CPF.

Thanks Vectrex!!!

(or should i say 'thanks HKJ!' ;) )

No, you shouldn't. Stop over-interpreting my posts. ;-)

HKJ made some worst case scenarios for Voltage readings.

Look for cheap DMM (digital multi-meter) recommendations here or on CPF.

Lensman one general advice... try to post those questions in the according sub-forum(if you can find them)... otherwise Information will be scattered around more than it already is and it gets harder to find.

Yes, Flashlight Wiki is a amazing body of work, and hats off to brted for taking so much time and trouble. But with such a big subject there's a limit to how much specific detail can be covered by one person, or even two or three. E.g., I've tried "how do I take a tailcap reading?" in FW's search box and got no result, even after re-phrasing the question several different ways. Is there a "LED Flashlights For Dummies" book? I'd buy one in an instant..

Meantime, I'll read through HKJ's excellent article again, maybe this time I'll understand it a bit better. Perhaps I'm just thicker than the average apprentice flashaholic, but whereas kreisler might need help getting the hang of his MM (same here, of course), I don't even know what a 'tailcap reading' is. Or, just as important, what it actually means, or why these readings are so necessary. But I won't give up. I have to learn how to mod that torch to send to you. You know the one, no constant output but a choice of ten different blinky modes..

Thanking for the links.. it's just.. i cant post my questions there, i am banned on cpf

If i measure an Eneloop cell, i would get a reading like

"1.1873 V ±(0.1%+2)",

or "4.2108 V ±(0.1%+2)" for a LiIon cell.

Tailcap current would be

"193.78 mA ±(0.5%+10)" on Low mode, and

"0.7463 A ±(1.2%+50)" on High mode.

Since i dont know this kind of notation (and i didnt get the cpf post), is anyone able to write down the calculation (equations) of the four ranges for the 4 cases?

Or maybe i should just give up, cancel the DD order, and go watch 2 movies in the theatre with the saved money.

or maybe watch only 1 movie but ask a Spanish girl to go with me to the cinema :D (Of course i'd have my Romisen, Quark or AAA lights with me hehe).

@ kreisler: ".. it's just.. i cant post my questions there, i am banned on cpf "

I can't understand that. All you did was suggest that Zebralight were Ultrafire clones. Come to think of it, Vectrex encouraged you.. You baaad boys!

He would have found out how CPF works sooner or later by himself and I used enough smilies to show that I was half joking.... a new account is easily made though. Welcome to the club of ass baiters kreisler... I think we need some sort of medal for that.

well, some of the mods (and probably some dealers too) got pi$$ed by my signature (which i adopted for BLF, see my sig) and when i repeatedly mentioned in my posts "i've ordered it too. but from DX. see my sig. .." they saw RED. later i found out that they call it "shilling" :D and that it was one of the main reasons for the ban

i plead not guilty, though.

$56? That's more than I paid for my Fluke...

which Fluke model is it? bought brand new?

Fluke 15B, brand new in shop.

how to get the worst case upper variation =Voltage*(100% + 0.1%) + 2 counters up on the last displayed digit

1.1873 * (1.001) + 0.0002= 1.1886873

how to get the worst case lower variation =Voltage*(100% - 0.1%) - 2 counters down on the last displayed digit

1.1873 * (0.999) - 0.0002= 1.1859127

On my cheapo Voltcraft I "loose" one digit when switching from the -2V range (eg 1.187 V) to the -20V range (eg. 1.19V). From my experience I can say that the variation is "normally" not even close to that maximum tolerance.

But if we take it any further than that... please in one separate DMM thread. I wouldn't pay that kind of money to only measure Voltages (safety) ... for current measurements (recreational bragging rights) it is probably a good investment.

@Lensman: Tailcap reading is nothing you "need" to do , but you "want" to do. Whereas Voltage reading of freshly charged cells is a pure safety measure because you don't trust your $5 charger not to overcharge your LiIons batteries (14500 and 18650)... if you only use NiMH (Eneloops) and high quality chargers you don't "need" a DMM at all. The joy of getting tailcap current readings is in the satisfaction you get, when an XM-L is driven at full 3A or an XP-G is driven at full 1.5A, so that the driver is pushing the maximum allowed current to the emitter, because almost all manufacturer are too cowardly to drive them at full power.

If you find any irony in this post .... you can keep it.


This is finally something which everybody can understand. An example of an equation or calculation. Thanks so much!! (…) So if my DMM displays 1.1873 V, it means that the true voltage lies somewhere in the middle between

1.1859 < 1.1873 < 1.1887

...and dropping another digit it would be correct to say 1.185 < X < 1.189

Hey, i mean, that's pretty accurate!! :D

(...)

Fluke 15B .. on Ebay 65€. Fantastic price you got, congrats!!

Reichelt has also the Uni-T line ....and if you need more selection

ouch.

It's a Wiki and I'm sure brted would love if more people would participate. Make an account and write an article about measuring Voltages/Current and let someone read it. That's how Wikis work... the first draft hasn't to be perfect. If you ask HKJ nicely I'm sure that you are allowed to use some of his stuff to make it more beginner friendly. You are in the perfect position as you still see the subject as a beginner... the pros are already too deep on the sophisticated side and probably use a too complex vocabulary for beginners.