Fluke 114 DMM, accurate enough for Lith-ions?

[lrp]

Thanks!! If it is, this will be the DMM I'll order!

 

[HKJ]

Thanks!! If it is, this will be the DMM I'll order!

More than enough, at 4.2 volt the error will be below +/- 0.023 volt.

But it does not have current ranges.

 

[Justin Case]

I disagree. True that the usual charging termination spec is 4.20V +/-0.05V, so that an error of 0.023V is within that range. But if you are more conservative than that and want to keep the charge voltage at 4.20V max, then the Fluke 114 accuracy is not sufficient to determine that. You don't know if a reading of 4.200V is 4.223V or 4.177V.

At that price, why not look into the Protek D620 at Circuit Specialists.

 

[alpg88]

Range/Resolution: 6.000 V / 0.001 V
Range/Resolution: 60.00 V / 0.01 V
Range/Resolution: 600.00 V / 0.1 V
Accuracy: ± ([% of reading] + [counts]): 0.5% + 2
http://us.fluke.com/usen/Products/F...=FlukeUnitedStates&Category=HMA(FlukeProducts)

 

[MorePower]

I disagree. True that the usual charging termination spec is 4.20V +/-0.05V, so that an error of 0.023V is within that range. But if you are more conservative than that and want to keep the charge voltage at 4.20V max, then the Fluke 114 accuracy is not sufficient to determine that. You don't know if a reading of 4.200V is 4.223V or 4.177V.

At that price, why not look into the Protek D620 at Circuit Specialists.

I, however, agree with HKJ that it's good enough. The difference in lifespan of a lithium ion cell charged to 4.200V vs 4.223V is small enough that you'd never notice it in normal flashlight use. Also, unless you're monitoring cell voltage with your DMM during charging to make sure you stop at exactly 4.200V, you're at the mercy of the cutoff of the charger as to when charging stops.

@ lrp: See, that's why the internet is so great. You can get two diametrically opposed answers from complete strangers in a matter of hours. :twothumbs

 

[soulrider]

Thanks!! If it is, this will be the DMM I'll order!

I have to ask. Is this something you need for your job or some other serious use or is it just something you'll be getting to casually check voltages on your rechargeable batteries? Please forgive me as I'm very new to flashlights and don't mean to offend. Also, I understand everyone places different value on items and what is expensive to one person is not that expensive to another. With that said, I'm also looking for a cheap (to me) multimeter for simple, casual hobby use and checking voltages on rechargeable batteries in the future. For the life of me I can't get my mind around spending $100+ on a DMM for casual use. If I was using it for my job, etc then it wouldn't be an issue. But for casual use I just have a hard time with it but maybe that's just me. Does one really need to spend this kind of money on a DMM for casual use to get an acceptable level of accuracy?

As for the issue regarding the accuracy, if I'm looking for 4.2 volts on a battery and the reading could be 4.177 or 4.223 because of the margin of error, is this not accurate enough?? If the voltage is really 4.177 are you going to put it back on the charger to eek out that 3 hundredths of a volt? Again, I don't mean to offend anyone. I'm still learning and want to understand the 'why' on some of this stuff.

 

[Justin Case]

If the voltage is really 4.177V, I probably wouldn't bother putting it back on the charger. But if I got 4.223V hot off the charger, then I personally would get a different charger. One doesn't have to monitor voltage during charging to identify what I would consider an unsat charger that goes above 4.20V.

My point, which was missed, is that the Fluke 114 might be good enough. I cannot agree that it is good enough. I didn't say that the Fluke was categorically not good enough. It depends on your requirements for things like cycle life, capacity, and even perhaps how capacity changes with charge cycles.

See this reference, for example:

http://powerelectronics.com/portabl...y_charger_ics/804PET22li-ion-battery-life.pdf

Also, let's say you are willing to tolerate 4.223V terminating voltage. Well, what is the true voltage? Is it as low as 4.200V or as high as 4.246V? Now the upper limit is getting to a non-trivial overvoltage IMO.

 

[MrGman]

Its not good enough because at some point in time you really want to measure the current through the battery into your load and you have no ammeter with that unit at all. Measuring current through the batteries into the load with a fresh charge on it typically tells you more about the battery and of course how well your item being run by the battery is working. In the case of LED flashlights, you will get to the point where you want to know the turn on current and current draw when the battery are fresh or are mostly discharged. A voltmeter is not enough. You want a good multimeter that can also measure current up to 10A scale accurately. So pretty soon you will be wishing you had a completely different meter anyway.

 

[DM51]

I'm moving this thread to the Batteries/Electronics section where it belongs.

 

[MorePower]

Also, let's say you are willing to tolerate 4.223V terminating voltage. Well, what is the true voltage? Is it as low as 4.200V or as high as 4.246V? Now the upper limit is getting to a non-trivial overvoltage IMO.

If the Fluke in question read 4.200V, and was off by the specified maximum of +0.023V, then at most you'd be have a 4.223V termination. 4.223V is not too bad in the grand scheme of things for a lithium ion cell.

From the PDF you linked, there's a curve showing cycle life vs float voltage. 4.200V vs 4.250V give 500 cycles and ~400 cycles to 80% initial capacity respectively, with 4.250V having 5% more capacity to start with than 4.200V charging. Would you notice 400 vs 500 cycles? Maybe. Would you notice 5% more capacity per charge? Maybe. Is 4.250V unsafe as a termination voltage? No.

More important is the fact that 4.200V is not an absolute for lithium ion cells. Depending additives and other active components, 4.100V might be the termination voltage needed to reach 500 cycles to 80% capacity, or 4.300V might be okay. There are too many variables to make worrying about 0.023V worthwhile.

The Fluke meter would allow checking of cells to make sure they weren't horribly over charged or over discharged. It seems that's all the OP is looking for.

 

[Justin Case]

IMO, overpriced for the given ccuracy specs. Also, no amps measurement capability to measure things like tail current and driver output current. I think there are better choices.

 

[HKJ]

IMO, overpriced for the given ccuracy specs. Also, no amps measurement capability to measure things like tail current and driver output current. I think there are better choices.

It is a bit like buying SureFire or from DX.

Fluke is not the cheapest or best specified meters, but they are very dependable.

 

[clintb]

I know Fluke meters are great (I have one, among others), but I just don't see the need to outlay the kind of cash it requires to get into the Fluke club when being used for flashaholic related stuff.

Here's a great deal for $139 US, and does just about everything a budding flashaholic could want, or need. As far as I can tell, the Protek is $10 US more than the Fluke, but it does so much more.
http://www.circuitspecialists.com/prod.itml/icOid/9052

 

[Justin Case]

If the Fluke in question read 4.200V, and was off by the specified maximum of +0.023V, then at most you'd be have a 4.223V termination. 4.223V is not too bad in the grand scheme of things for a lithium ion cell.

From the PDF you linked, there's a curve showing cycle life vs float voltage. 4.200V vs 4.250V give 500 cycles and ~400 cycles to 80% initial capacity respectively, with 4.250V having 5% more capacity to start with than 4.200V charging. Would you notice 400 vs 500 cycles? Maybe. Would you notice 5% more capacity per charge? Maybe. Is 4.250V unsafe as a termination voltage? No.

More important is the fact that 4.200V is not an absolute for lithium ion cells. Depending additives and other active components, 4.100V might be the termination voltage needed to reach 500 cycles to 80% capacity, or 4.300V might be okay. There are too many variables to make worrying about 0.023V worthwhile.

The Fluke meter would allow checking of cells to make sure they weren't horribly over charged or over discharged. It seems that's all the OP is looking for.

My point was that if the DMM reads 4.223V, apparently that is still satisfactory for you. But due to the relatively poor 0.5% range accuracy of this Fluke, the reading could be as high as 4.246V.

"Horribly" overcharged is in the eye of the beholder. I am unsatisfied with a charger that goes over 4.20V. For me, it's binary. It's either go or no-go. So I want a meter that can differentiate between 4.20V vs. 4.21V or 4.22V or 4.23V. I don't mind paying the price for a good Fluke like an 87-V, but I also expect accuracy specs better than that for a cheap DMM from Harbor Freight. An 0.5% range error simply doesn't cut it. The saving grace for the 114 is that it has a 6,000 count display. Otherwise, the high range error plus the 2 digits of offset error would really kill it.

The curves in the referenced PDF are notional, since different Li-ion chemistries have different performance. It is precisely because there are so many variables that I would want to eliminate the one variable I can control -- voltage measurement accuracy. And it just so happens that it is an important variable.

Now, you may still get this Fluke 114 and also combine it with a voltage reference such as the one from Malone Electronics. That can then give you a solid idea as to what the measurement error is. But until then, you just don't know. Does that matter? It does to me. It doesn't for others.

 

[Justin Case]

It is a bit like buying SureFire or from DX.

Fluke is not the cheapest or best specified meters, but they are very dependable.

Ok, overpriced for the accuracy spec, but at least reliably overpriced and inaccurate. But still sadly limited in functionality since it can't measure current, which is another important measurement in characterizing flashlight performance.

I suggested the same Protek D620 meter from Circuit Specialists that clintb did.

 

[Scott Packard]

> For me, it's binary. It's either go or no-go.

You're measuring a fundamentally chemical reaction. It isn't binary. The reaction is logarithmic.

 

[Tom_123]

As I was on the market for a DMM as well, I dare to share my humbly opinion.

Accuracy:
The advertised specs reminds me somehow to advertising lumens for a flashlight;
you'll never know if they are correct.
For a better accuracy, you want to calibrate your DMM or at least
compare it to a well calibrated meter.

Fluke:
Fluke is nice but incredibly expansive if not to say overpriced.
The 11x series is considered entry-level.
E.g. on a plant/ lab the Fluke 114 would be the meter you would hand out
to a trainee to make sure he don't kill himself while measuring (CAT IV 600V and no current setting)
and that you don't have to buy him a new meter every week.
If you want to go the Fluke way for precise electronic measuerement,
you will have to invest even more. I'd say the Fluke 175 is the entry level for that purpose.

Does it make sense to buy a Fluke to check batteries?
IMHO, not just no, but absolutely no.
These meters are for the pros or die hard electronic geeks.
You will pay for a lot of things that you will never need,
like brand name, compliance and certification for a lot of standards, and the like.
In addition, a high price doesn't necessarily mean higher accuracy here. (see above)
Further, voltage measuring is easy to implement, so every reasonable DMM would do a good job here.

So what would I recommend:
- As no one can rule out the possibility completely, that the meter will be used some day for
high voltage measurements, the DMM should at least comply with CAT III / 600V.
(better save than sorrow)
- The current ports have to be protected by fuses.
- Accuracy for voltage reading should be 0,5% or better.
To compare the accuracy between DMMs according to the specs,
rather look at the current settings.
- Seeing all the nice charts here at CPF, you may get inspired to do some chart yourself,
so maybe consider to get a DMM with a data logger.
- A temperature setting may be useful as well.

If you want a known/respected brand, maybe Amprobe is the better choice for your purpose.
May take a look at the 38XR-A (data logger) or the 37XR-A.

As an alternative to the recommendations above, maybe also take a look at Uni-Trend.

http://www.uni-trend.com/

I can't say much about the quality yet, as I just ordered one. (UT71C)
The specs are promising though.

If you don't need all these bells and whistles, I dare to say, every not too shabby
DMM in the $50-$80 price range will do a good job for checking batteries.

Hope that helps somehow
Thomas

 

[Justin Case]

> For me, it's binary. It's either go or no-go.

You're measuring a fundamentally chemical reaction. It isn't binary. The reaction is logarithmic.

So what. If the charger uses a terminating voltage over 4.20V, I get rid of it. That's my binary decision.

 

[BoarHunter]

When it comes to tools and measuring equipment, get the best you can afford.
It is for life !

Current, Temp, RMS, frequency. Yes if you are serious about the hobby.
Now if it is just to check a battery condition ?

And as said above, when it comes to electric equipment, poorly insulated or poorly protected equipment may lead to your life being short circuit!


And please, do some learning about it. I am amazed how basic things like voltage, intensity etc... seems to be mysterious while every 16 years old should know about !

Isn't it part of basic education anymore ?

 

[koala]

If you are looking for information regarding multimeter accuracy then you better to be prepared spending some cash. Seriously, don't go the cheap route, you will just end up with more meters.

If you are looking at a Fluke, then I suggest not a Fluke 114 because it's just not economical for the 0.5% basic dc accuracy. Spend a little bit more, and get one with 0.1% or lower.

As mention above, Uni-Trend is a very dependable and reliable brand. They are probably the biggest monopoly in the multimeter market. Uni-Trend is a contractor and make many and most rebranded, for example Tenma.

I have a UT71D and it's has a DC volt accuracy of 0.025% which matches my Fluke 187. I haven't found any unacceptable drift over the pass two years since I bought it. This is based on one sample that I have. However, the UT71D is not cheap. I'm not saying you should buy a Uni-Trend here, I find some other measurements a little unstable when there's noise. It takes a while(10-15sec) for the Uni-Trend to settle down when measuring capacitance. The Fluke always give an accurate result and the measurement is repeatable.