Accurate Universal Voltage Meter?

[hk dave]

Hey guys... as I'm becoming a flashlight fanatic, and spending countless hours reading up here at CPF, it suddenly dawned on me that it would be pretty cool to have some kind of voltage meter!

Anyone have an suggestions on a decently priced meter?

I mostly run 18650, 14650, cr123, AA, D batteries. I charge the li-ions with an Ultrafire charger.

Are there special functions I should be looking for in a voltage meter? Are they all pretty much the same?

Would appreciate any input. I'm really new to this stuff and hate buying a bunch of things that don't work out.

Thanks!

 

[Bullzeyebill]

Welcome to CPF. Glad you are doing some reading and I can give you some clues how to research voltage meter. Try the Google, cpf only bar at the top of every CPF page and write in voltage meter, or DMM (digital multi meter) and maybe add "good" to voltage meter or DMM. Good DMM. Try some other combo's and you will come up with some results. The reason I say this is because there are many threads with more or less the same title as yours, except maybe the word "Universal". DMM in the heading will draw more hits. I think that there is a current DMM thread going right now. Some of our CPF people will give you some ideas, and you can add that info to what you will find elsewhere here on CPF.

Bill

 

[Flint&Steel]

Hey Dave,

I'm a newbie myself, and I took the advice of everyone here that "you need a DMM if you're going the Li-Ion route", so I went to Sears and bought a Craftsman digital multimeter for $19.99.

Based on my (very) limited experience, the consensus on CPF is that the AW RCR123's should come off the charger at 4.17/4.18, and those are exactly the numbers my DMM gives me, so for 20 bucks it seems to be working fine and enough to give me accurate readings.

From my understanding, the only feature for checking batteries you'll need is a DC setting of 20V.

I'm sure there are cheaper DMM's out there you can buy online and wait a week to get, but it was one day from the time I decided I needed a DMM until my batteries arrived, and I had to have one NOW! (new man toy! new man toy!) And Sears is just 5 mins. from my house

Take the advice of the wiser folks on here, I was just giving you a fellow noob's experience. I'm sure if you're like me and we keep taking advice from the wiser folks, we're gonna go broke (my next three lights are already chosen, pending funds).

Whatever you do, definitely get one!

Flint

 

[VidPro]

Are there special functions I should be looking for in a voltage meter? Are they all pretty much the same?

!

one thing i always prefer to have in a meter , is the 10Amp Ammeter/current ability, if it has that and is reasonably accurate then it'll work. if you only need voltage you can often get them for cheaper, and RS has a cool pocket meter that is acurate enough. but when you really get down to Using it for lotsa stuff, being able to check 1-9.9amps inline with something becomes very usefull to tell consumption currents.

 

[march.brown]

.
If you are really looking for an accurate meter, get a really cheap digital meter for a few $ or £ plus a "Precision Voltage Reference Source, 5.000 volts, 0.02% accuracy" ... I have just sent for one of these at a cost of $14-55 (£9-44) plus postage to the UK (off Ebay) ... All you need to do is check what your cheap meter reads for the reference voltage and that will show you how far off your meter is at five volts ... This means that you can accurately correct the 4.2 volt cell reading to within 0.02% or better ... I use a Maplins £4 or £5 meter which has an accuracy of 0.8% on the 20 volt range (0.5% on the one volt range) ... So this device is at least 40 times more accurate than the meter ... You won't get better accuracy anywhere for this price.

The 5.00 volt Reference will work on any meter ... I will check my meter every month or so just to be certain that the cheap meter is still OK ... This is still a more accurate method than relying on a mega-expensive meter alone ... You might have friends in electronics who could build you one cheaper ... I considered that, but this one comes with a statement of how far it is away from 5.000 volts, so it can give you an absolute value better than 0.02% ... That is good enough for most people.
.

 

[TranceAddict]

nothing beats FLUKE :thumbsup:

 

[hk dave]

Thanks for the input guys...

So DMM is what i need. That was my first issue, didn't know what it's called. haha

What do you guys think of the Fluke 77 IV Digital Multimeter? Can be had for $20 or so.

I wonder if it will give me a reading on Alkalines, Lithium Ion as well as cr123 primaries?

 

[hk dave]

LOL... nevermind... the link i found for $20 was incorrect. This thing costs like $250...

Time to look for something cheaper. :P

 

[space-time]

Umm.... electrical engineer here. :D Don't forget the load when you are testing battery voltages (pulling an amount of current out of the battery roughly equal to the expected usage current). Testing open-circuit (no load) is good for finding completely shorted batteries, and seeing what the maximum (static) charge level is at after charging rechargables, but what you really want for a go/no-go test is the battery voltage when under full load.

The same goes for car batteries or any other type of battery. To truely check a car battery you need to test it under full cold-cranking amps load, 400-600 amps, and do it for roughly the length of time you will be cranking the car, like 30 seconds. FWIW, Wal-Mart auto centers has an automated tester that will do exactly that these days and printout the results.

What you will find is a lot of ("dead") batteries "recharge" under no-load (static) conditions to their full rated voltage. But once an operating current load is put on them they quickly (seconds or minutes) go down in voltage below operating parameters. That leads to the situation of people testing a battery with a no-load tester, which shows "good", then putting it in a flashlight or remote control only to find out its dead.

Unfortunately I don't know of any off-the-shelf full load units for NiMH or Lithium to point you too. I just use resistors and do the math.

 

[march.brown]

.
If you are really looking for an accurate meter, get a really cheap digital meter for a few $ or £ plus a "Precision Voltage Reference Source, 5.000 volts, 0.02% accuracy" ... I have just sent for one of these at a cost of $14-55 (£9-44) plus postage to the UK (off Ebay) ... All you need to do is check what your cheap meter reads for the reference voltage and that will show you how far off your meter is at five volts ... This means that you can accurately correct the 4.2 volt cell reading to within 0.02% or better ... I use a Maplins £4 or £5 meter which has an accuracy of 0.8% on the 20 volt range (0.5% on the one volt range) ... So this device is at least 40 times more accurate than the meter ... You won't get better accuracy anywhere for this price.

The 5.00 volt Reference will work on any meter ... I will check my meter every month or so just to be certain that the cheap meter is still OK ... This is still a more accurate method than relying on a mega-expensive meter alone ... You might have friends in electronics who could build you one cheaper ... I considered that, but this one comes with a statement of how far it is away from 5.000 volts, so it can give you an absolute value better than 0.02% ... That is good enough for most people.
.

.
TransAddict ... Are there any Fluke meters (at any price) that can give better than the 0.02% accuracy of the "Reference" device ?

Certainly not for the price of a cheap DMM plus the Reference Device which would be about $25 total ... My last Fluke cost a fortune and was about one tenth of this accuracy, maybe even worse than that, but I didn't need an ultra high accuracy meter then ... It is my personal preference that I want the highest accuracy at the lowest price to check the Li-Ion cells with ... I shudder to think what even a 0.1% Fluke would cost ... I'll just stick with the cheap and more accurate method, rather than the expensive and less accurate one.
.

 

[HKJ]

.
TransAddict ... Are there any Fluke meters (at any price) that can give better than the 0.02% accuracy of the "Reference" device ?

Certainly not for the price of a cheap DMM plus the Reference Device which would be about $25 total ... My last Fluke cost a fortune and was about one tenth of this accuracy, maybe even worse than that, but I didn't need an ultra high accuracy meter then ... It is my personal preference that I want the highest accuracy at the lowest price to check the Li-Ion cells with ... I shudder to think what even a 0.1% Fluke would cost ... I'll just stick with the cheap and more accurate method, rather than the expensive and less accurate one.
.

This is a bit like the discussion about what light you buy, why buy a $500 Surefire, when a $30 DX can do the same.
On a good day with the correct temperature, the cheap solution might have a good precision on DC volts, the expensive meter will have a good precision on all ranges, every day, independent of the weather and will not give wrong results, when the batteries are running out.

For checking LiIon batteries the cheap solution with a reference is very good, but for more serious use I would take the expensive meter every time (I am using a Fluke 189 most of the time).
I did a guide on using DMM's here with both the Fluke and a cheap meter.

 

[march.brown]

This is a bit like the discussion about what light you buy, why buy a $500 Surefire, when a $30 DX can do the same.
On a good day with the correct temperature, the cheap solution might have a good precision on DC volts, the expensive meter will have a good precision on all ranges, every day, independent of the weather and will not give wrong results, when the batteries are running out.

For checking LiIon batteries the cheap solution with a reference is very good, but for more serious use I would take the expensive meter every time (I am using a Fluke 189 most of the time).
I did a guide on using DMM's here with both the Fluke and a cheap meter.

.
I really only needed an accurate digital voltmeter to measure the 18650s and the charger volts, hence my choice of a cheap meter plus the reference device (to check the accuracy at exactly five volts) ... So, it should be great at checking accurately the 4.2 volts reading ... If I want to be really accurate, I can check the cheap meter each time I use it, which would probably be once a week or so ... The reference device is accurate over a good range of temperatures and only uses a few pico-amps so can be left on permanently for stability ... It uses a small nine volt battery.

For current measurements and for non-critical measurements, I tend to use my analogue Avo 8 meter.

I also have a more expensive DMM which cost about £10, so this will have its voltage readings checked in the same way as the cheap one.

Since, at the moment, I only have eight 18650 cells, I didn't want to spend a lot of my pension on a highly expensive meter.

I don't mind spending four or five pounds on a new meter every year or two as and when necessary.
.

 

[HKJ]

.
For current measurements and for non-critical measurements, I tend to use my analogue Avo 8 meter.

Analog meters are not very high accuracy.

I also have a more expensive DMM which cost about £10, so this will have its voltage readings checked in the same way as the cheap one.

Before I call a DMM expensive it must be a few 100.

Since, at the moment, I only have eight 18650 cells, I didn't want to spend a lot of my pension on a highly expensive meter.

A cheap meter is much better than no meter and with a reference you have a very good setup (At least for DC voltage), because if either the meter or the reference fails, you will see it.

 

[uk_caver]

.
If you are really looking for an accurate meter, get a really cheap digital meter for a few $ or £ plus a "Precision Voltage Reference Source, 5.000 volts, 0.02% accuracy" ... I have just sent for one of these at a cost of $14-55 (£9-44) plus postage to the UK (off Ebay) ... All you need to do is check what your cheap meter reads for the reference voltage and that will show you how far off your meter is at five volts ... This means that you can accurately correct the 4.2 volt cell reading to within 0.02% or better ... I use a Maplins £4 or £5 meter which has an accuracy of 0.8% on the 20 volt range (0.5% on the one volt range) ... So this device is at least 40 times more accurate than the meter ... You won't get better accuracy anywhere for this price.

The maximum precision of reading for a 0-1999 display meter (or a 0-3999 display meter) for a 5V or 4.2V measurement is only going to be the nearest 0.01V, that is, the nearest 0.24% for a 4.2V measurement.

 

[hk dave]

Wow... i feel like a truly young grasshopper.

What should i get for under $50? :)

 

[march.brown]

Analog meters are not very high accuracy.

But I did say that I didn't need high accuracy other than for volts ... My charging current measurements are not as critical as the measurement of the 4.2 volt reading ... I am not worried about my charging current measurements being super accurate, except for the final "end of charge" check which will be on a milliamps range ... These current checks will only be carried out once or twice just to prove that the chargers are OK ... My Avo 8 is therefore more than adequate for my non-voltage use.

Before I call a DMM expensive it must be a few 100.

You are very lucky to be able to justify this sort of cost ... Some of us unfortunately are not.

A cheap meter is much better than no meter and with a reference you have a very good setup (At least for DC voltage), because if either the meter or the reference fails, you will see it.

Thank you for the commendation ... I am very happy with this low cost option plus I also have a second £10 digital meter as back-up ... It would be very nice to have an expensive Fluke meter again, but on my income I really cannot justify the huge expenditure ... Since being made redundant sixteen years ago, I do the best I can on the available funds.

The same applies to my choice of torches ... Much as I would like to have some expensive torches, for me, my three Solarforces plus other cheapies are more than adequate.
.

 

[march.brown]

The maximum precision of reading for a 0-1999 display meter (or a 0-3999 display meter) for a 5V or 4.2V measurement is only going to be the nearest 0.01V, that is, the nearest 0.24% for a 4.2V measurement.

.
So the reading is to two decimal points ... That means that I can measure to within 5 millivolts (plus or minus) ... Anywhere between 4.195V and 4.205V should show as 4,20 volts ... 4.206 should show as 4.21 V ... That is accurate enough for me ... Even 10 millivolts would be OK.

Both my meters are 0.8% on the 20 volt range, hence the need to check against a known reference (in this case 5V plus or minus 0.02%).

Irrespective of the reading on the display when used to check against the reference, I will have a readout for the five volt reference ... I will apply a correction factor to the 4.2V figure to arrive at a very accurate reading ... Certainly good enough for me.
.

 

[Lynx_Arc]

not knowing where you are at, I would say till you can afford a high quality DMM, the harbor freight DMMs are acceptable for what you want and very inexpensive on sale perhaps $3 each. I use a battery tester on everything but li-ion that has 3 load settings I got from steves wholesale tools where I am at. It has a digital readout cost me under $10 local and is a lot easier than fumbling with test leads and figuring out load resistors to make sure on weak primaries.

 

[march.brown]

not knowing where you are at, I would say till you can afford a high quality DMM, the harbor freight DMMs are acceptable for what you want and very inexpensive on sale perhaps $3 each. I use a battery tester on everything but li-ion that has 3 load settings I got from steves wholesale tools where I am at. It has a digital readout cost me under $10 local and is a lot easier than fumbling with test leads and figuring out load resistors to make sure on weak primaries.

.
At the age of 72, I doubt very much whether I will ever be in the position to afford (or justify) the cost of a very expensive DMM ... There are other much higher priorities unfortunately.

In the UK (£5 at Maplins), they have a meter that looks exactly like the Harbor Freight one ... This is my cheaper one and seems to be very reliable ... I also have a cheap analogue battery tester for non-Li-Ion batteries, though mine only has a single load resistor ... It seems to work reasonably OK on primary AA and AAA batteries ... The one that you have sounds to be a much better designed version and a good price too for a digital readout ... I haven't seen any like that in the UK ... I must have a look on Ebay.
.

 

[poguy]

Go to Harbor Freight ("Tools for Fools") and pickup their $1.99 special, it's better than you think. The one I have agrees with a more expensive meter.

I wouldn't buy a used one. Many will have been abused.