Small volt meter - how to set value?

unclebob

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Jul 11, 2018
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So I've ordered a bunch of the small volt meter display, what's the best way to make sure it's displaying the correct value? I was thinking of just taking a cell, see what opus says, and then set the meter to show the same on the same cell... But is there a better way? My actual multimeter only shows DC to the nearest volt so no good to set with.
 
"Correct" is a relative term. How do you determine what is correct and what isn't? You need a reference that is treated as the baseline. I use my Fluke 115 multimeter for this purpose and calibrate every other device against it. If calibration is possible that is. If you have no better choice than the Opus then use the Opus.

"Better" as in better way is also relative. The best way would be using a reference with the highest possible accuracy. But if you don't have such a device what are you going to do? You have to work with what you have or what you are prepared to buy for this purpose.

And finally, at the end of the day consistency could be more valuable than accuracy. Doesn't matter if it is 3.51V or 3.52V as long as it is either of them all the time and on all devices. That said it should be accurate down to 10mV or 0.01V at least when dealing with batteries. Most devices will get this right though.
 
Cheers DarkRaven, i suspected as much.

Im waiting for silicon wires for my opus. Once i have them i will set all 5 of my multi meters against a cell measured in that, can then test on a couple of other cells to make sure they read the same, and also set my 5a psu as well.

Until i get a meter which is actually designed to measure low voltage on DC I'm a bit limited... My current one only does 1v on DC. Its a Fluke T5-1000 - seems to be designed more around ac and higher voltage/resistance. No good for low resistance or voltage!
 
unclebob said:
But is there a better way?

Yes, there is!

1. Buy an AD584L-based voltage reference module. The L version is more accurate than J and K ones. They cost about $4.5. You can check and calibrate your multimeters with it and then check with multimeter how much does your Opus lie (or does not).

2. Buy a good multimeter with high accuracy like UNI-T UT61E or, if you look for a cheaper one, ZT102.

And never try to check the voltmeter using the voltage shown on Opus or something like that.
 
If you want to do a really cheap method is calibrating from a Duracell AA cell. They are specifically designed to be 1.619V. This has been verified by many different people doing calibrations and backed with several different Fluke MM's

Here's a quick explanation:

 
thunderheart said:
Cherry67 said:
There are many more voltage reference ICs than the AD584,
Did i say AD584 is the only one?

Cherry67 said:
But the AD is sure a good choice
That's why i recommended it. :D

Touche.... :D
 
I second the recommendation for a UNI-T UT61E

While I have a couple Fluke meters, and other various electrical testers... I love my UNI-T UT61E. For the money, you cant find a better budget meter for low voltage DC electronics projects. Its a 22,000 count meter and the resolution and accuracy is great for what it is.

On top of all that, resistance measurements are solid, PC connecting for logging / testing. The only thing I dont like about it is it has a high burden voltage for higher current measurements, but I could care less because I have a small arsenal of DC clamp meters for that purpose anyways.

While you are at it, pick up a UT210E clamp meter too.

$100 for both its a good investment.
 
Ended up getting a Zotek - ZT102 - did the duracel test and got 1.627V from a brand new cell - Duracell Plus Power - Best before Mar 2027- Box code is 81258634OD.

Also tested one i had sitting around for a few months - 1.624V - Same type of cell, and best before date - Box code is 80038634PN.

Basing on the new cell voltage im reading approx 0.008 V over - but no where inside to calibrate so i guess a sticker on the screen to remind me is as close as i get for now! as long as everything is reading from the same, there's no problems. I can set my PSU and all of my mini voltage display's correctly based on that value, and can double check by putting the voltage display against the duracell directly to see what it reads. Will do for now, while im still processing, will look to get something better once i get closer to building.
 
Well looks like someone bought their first meter... congrats.

Personally I wouldn't go calibrating that meter yourself... unless you own some pretty professional grade calibrated equipment and or some voltage references, I would leave good enough alone. Certainly do not use a battery as a reference.

If you want to start learning more about test equipment, I do like this guys channel... Hes all about that stuff and his reviews are the ones that convinced me to get a UT61E


At least you have something you can use to setup your small volt meters.... it will be good enough, but I think the longer you own that and the longer you use those small volt meters you will eventually see their deficiencies.

Its fine for general monitoring, but don't rely on them for the correct answer, they do drift over time and if you calibrate for 3v, they will often times be off at other voltages the farther away you go from it's set point.
 
Lol its actually my second one - the first one - a fluke cant do dc voltage to less then 1 decimal place... kinda awkward when trying to measure voltage drop!

Re calibration, just wanted to get an idea of how far it was off, meter is too cheap to be able to adjust, but only looking for something to give me an idea of volt drop at the moment, once i've got enough cells (hard to get hold of in the UK!) to do something meaningful with them, i'll invest in a proper meter... at the moment, ive just got a box file of cells i need to charge, test and then put away again :D

the small meters are mainly to show bump charging values between two cells, and as a basic checker - each end connected to a single cell holder so i can quickly put a cell in and get an idea of its current state as i pull them out of packs.. as long as its not out by over a volt, it will be sufficient for me to know if it is a bin, bump charge or straight into TP4056 kinda sort.
 
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