# Good cheap multimeter?



## Tommygun45 (Oct 24, 2011)

I have spent far too much on this hobby the past year. I already have the Pila charger and I know my batteries are fine but I am just sometimes curious as to what their charges are. Nothing too serious. What do I need to be able to read their voltage? Is it called a multimeter? Is there a good cheap one out there? I have shopped around but its just a bit confusing when im not 100% sure what I am looking for.

I have a bunch of AW 18650's, 17670s, rcr's, and a set of callies customs 3100mahs.

Thanks guys.

-Tom


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## Lynx_Arc (Oct 25, 2011)

http://www.candlepowerforums.com/vb/showthread.php?283653-Cheap-Multimeter
The harbor freight ones on sale are decent. As far as knowing the charge using the voltage as a reference is not typically an accurate way to do so unless you are very familiar with the charge left at the resting voltage of the particular battery. Meters cannot measure capacity left without draining a battery to do so.


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## Mr Happy (Oct 25, 2011)

Do you live anywhere near a Harbor Freight Tools? If so, I suggest you pick up one or two of these:

http://www.harborfreight.com/7-function-digital-multimeter-90899.html

Now, you are not going to get deluxe quality or durability for $4.99, but it will be a perfectly serviceable tool to learn what a multimeter is and how to use it. I have a few of them and they are quite accurate and functional. 

But just in case you are tempted, don't go anywhere near mains circuits with them, stick to low powered batteries. They don't have any safety standards at that price point.


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## Mr Happy (Oct 25, 2011)

Just to give you a quick heads-up: you measure lithium ion voltages with the DC volts setting on the meter, for example the 20 V scale on the Harbor Freight one. If the cell reads 3.7 V or less it needs recharging. When freshly charged it should read between 4.1 V and 4.2 V. If it reads less than 4.1 V when freshly charged it is showing signs of wear.


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## Moriarty (Oct 25, 2011)

Is a cheap multimeter all that is needed ?

I have a cheap one but is something like a ZTS Multi Meter going to be an advantage or is knowing the voltage enough ?

I have an Ansmann battery tester but sadly it does not work with the more exotic battery types such as 18650 etc.


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## march.brown (Oct 25, 2011)

Tommygun45 said:


> I already have the Pila charger and I know my batteries are fine


 You cannot possibly know that your Li-Ion batteries are fine without an accurate means of measuring the open-circuit battery voltage ... The state of charge of a Li-Ion can be easily checked by simply measuring its rested voltage ... There are tables available on CPF that will give you the Percentage Charge in the battery ... Obviously a reasonably accurate DMM is required , or a precision reference with which to check your meter.

No-one should put their faith implicitly on the charger alone ... That is irrespective of the make of the charger and its apparently good reviews ...

I use cheap meters but I know they are very accurate as I check them against a known high accuracy voltage reference device ... I check all my meters regularly and if one is not the same as the others , it is usually because the battery in the meter needs replacing ... If (or when) a meter is out of my limits , it is either thrown away or given to someone who doesn't need this degree of accuracy ... So far , I have only given away one cheap meter ... 

My meters are all identical to the Harbor Freight cheapies and bought here in the UK for less than £5 each.
.


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## samgab (Oct 25, 2011)

I've had a few really cheap DMM's over the years. They've all been pretty crappy, and I don't know how dependable the readings have been...
I recently got a Fluke 17B from China, for <$100.
I'm very impressed and completely satisfied with it, and expect it to last reliably and dependably for many years to come.
If you're looking for something at around the USD$80-100 price point, I highly recommend the Fluke 17B.
Cheaper than that, and while you'll get readings, you have to make sacrifices in terms of quality and reliability; in my experience.


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## cland72 (Oct 25, 2011)

Mr Happy said:


> Do you live anywhere near a Harbor Freight Tools? If so, I suggest you pick up one or two of these:
> 
> http://www.harborfreight.com/7-function-digital-multimeter-90899.html
> 
> ...



I can vouch for the HF multimeter -- I've had mine for about a year an used it on my rechargeables and my car with pretty good results. Nothing to complain about for $5.


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## xul (Oct 25, 2011)

Mr Happy said:


> don't go anywhere near mains circuits with them


Ditto. Arc-flash danger.


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## shao.fu.tzer (Oct 25, 2011)

My favorite cheap DMM is my Equus Innova 3320... I'm more inclined to take it out of the house since it only cost me $20 and has taken many harsh falls without breaking... I also have a JLY A830L that I got from one of "those" sites for something like $9 shipped that has gone through several battery changes without dying on me.


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## Mr Happy (Oct 25, 2011)

shao.fu.tzer said:


> My favorite cheap DMM is my Equus Innova 3320


Yes, I like that one too. Nice quality feel, big digits on the display, very small, wrist strap for working in confined spaces (wear it like a wrist watch), good robust case. Can find it in WalMart.

However, since it is sold and intended for automotive applications it is probably best not to use it on mains circuits just like the Harbor Freight one.


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## HKJ (Oct 25, 2011)

One "cheap" meter I thinks look good is the Vichy VC99, some of the good points are:



Display can show 6000, i.e. with LiIon batteries you get an extra digit (Like 4.123 volt, most meters will only show 4.12 volt).
No shared volt/current terminal.
It has fuses on both current terminals.
It has a nice selection of ranges.
Precision looks good
Has a yellow rubber protection around the meter.
But I have not used it enough to say how it stands up to daily use (I nearly always uses my expensive meters).







Only problem I have seen with the meter is the blue lettering, it is difficult to see.


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## Sci Fii (Oct 25, 2011)

I'm going to disagree about the Harbor Freight suggestion. I went and bought one of these on a similar suggestion. Lasted all of about 20 minutes until one of the plugs broke. Went to Walmart and bought the Innova Equus 3300. About $11. The HF unit was so cheap I swear it weighed about a third of the Innova unit. Spend the 6 bucks extra. I checked it against my uncle's Fluke and it's good enough for me. BTW, like you, I only use it for battery testing. I'm sure it's good enough to learn on if you want to do more.


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## CincyDawg (Oct 25, 2011)

shao.fu.tzer said:


> My favorite cheap DMM is my Equus Innova 3320... I'm more inclined to take it out of the house since it only cost me $20 and has taken many harsh falls without breaking... I also have a JLY A830L that I got from one of "those" sites for something like $9 shipped that has gone through several battery changes without dying on me.


 
+1 on the Equus 3320. Picked up one recently and have been pleased. Think Amazon has for about $16


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## Mr Happy (Oct 25, 2011)

Sci Fii said:


> I'm going to disagree about the Harbor Freight suggestion. I went and bought one of these on a similar suggestion. Lasted all of about 20 minutes until one of the plugs broke.


Yeah, that happened to one of mine too. But I bought four of them on sale at $2.99 each, so I was not too concerned. They are basically disposable at that price, and if you get the odd failure you just take the rough with the smooth.


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## moderator007 (Oct 25, 2011)

I have had one of the HF multi's for about two years. I have mistreated it becuse it was so cheap and i bought more than one. The thing still works great and is my general purpose go to multimeter. I dont have to worry about losing it or tearing it up. I do agree that spending a little more may buy you a better multimeter. But there is always lemons in everthing you buy.
The ideal setup would be one or two cheap meters and one accurate dependable meter.


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## Sci Fii (Oct 25, 2011)

It's not just that Mr Happy. The dollar amount here is not the important thing. There's something about using such low quality stuff that's it's almost demeaning to the user. Some low dollar stuff is OK or even quite acceptable. This is not one of those cases.


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## Mr Happy (Oct 25, 2011)

Sci Fii said:


> It's not just that Mr Happy. The dollar amount here is not the important thing. There's something about using such low quality stuff that's it's almost demeaning to the user. Some low dollar stuff is OK or even quite acceptable. This is not one of those cases.


OK, but I don't have the same experience. I broke the plug on mine because I was heavy handed and forced it. Apart from that the quality seems fine. It works, it's accurate, and the display is very readable with good contrast.


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## Lynx_Arc (Oct 26, 2011)

I have a half dozen harbor freight Dmms. I bought 3 and inherited 3 and all of them seem to work fine. I think they are on the cheapest side of the "good" multimeter. I have a craftsman DMM that has broken once needing repaired already that cost more than the 6 harbor freight meters. If you only need one meter you may consider investing in a $20 one instead of a cheap one. I prefer to have a good meter and a cheap one I can toss a cheap one in my car, keep two in the garage, 2 in the house and loan one out and still not have to worry about my $20 meter.


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## qwertyydude (Oct 26, 2011)

I have to also recommend the Innova 3320 from Walmart. It's accurate, and the only thing you gotta do is change out the leads to heavier gauge shorter wire if you're planning to do current measurements.


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## march.brown (Oct 26, 2011)

Sci Fii said:


> The dollar amount here is not the important thing. There's something about using such low quality stuff that's it's almost demeaning to the user. Some low dollar stuff is OK or even quite acceptable.


I guess that is the reason why some people buy expensive torches ... It is demeaning to be actually seen with a cheap torch ... I don't mind being demeaned (?) ... I don't have any expensive torches but I still have my immaculate (but very old) Avo Model 8 meter which still works perfectly ... I could even use it on my Li-Ions if I wanted to as the mirror scale makes it easy to read very accurately ... Checked against my five volt reference device , it is spot-on ... However it is so much easier to read my digital cheapie meters that the Avo is just left sitting on display in the study in its nice polished leather case ... The Avo 8 was a very expensive meter when it was bought for me about 37 years ago ... As I was working on electronics , I also had some Flukes for a few years ... The three Flukes all died and yet the old Avo 8 has carried on working as good as ever ... The Flukes were deemed to be beyond economic repair when in-fact it was only their display that had failed ... They had frequency measurement on them which was useful , but as I also carried a TMS and an SLMS with me that feature wasn't absolutely essential ... Luckily I wasn't paying for the Flukes ... 

My ultra cheap Harbor-Freight lookalikes are absolutely spot on in their readings of my reference and that is all I need for my Li-Ion voltage readings ... If a meter starts reading low , I check its battery and if that is not the problem I will dispose of the meter ... So far , I have given away only one meter that was 30mV out on the 20V range when measuring the 5V reference ... It was given away to my Son-in-Law 'cos it was still OK for him to check bulbs , fuses and NiMh batteries with.

So, cheap meters are OK as long as you can trust their readings ... All meters , even the most expensive should be checked against a reference that is at least ten times better (preferably more) ... Nowadays , you can have your reference checked annually for just a few dollars plus postage if you really need the ultimate accuracy.
.


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## Jakpro (Oct 26, 2011)

You can find cheap Fluke 12's and 113's on the auction site.


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## SemiMan (Oct 27, 2011)

march.brown said:


> You cannot possibly know that your Li-Ion batteries are fine without an accurate means of measuring the open-circuit battery voltage ... The state of charge of a Li-Ion can be easily checked by simply measuring its rested voltage ... There are tables available on CPF that will give you the Percentage Charge in the battery ... Obviously a reasonably accurate DMM is required , or a precision reference with which to check your meter.
> 
> No-one should put their faith implicitly on the charger alone ... That is irrespective of the make of the charger and its apparently good reviews ...
> 
> ...


 
Just because you can get an accurate voltage reading on one scale does not indicate that you can get accurate readings on all scales and all things you are reading. This has been my issue with cheap meters ... cheap switches and dials and flaky readings. I would certainly feel more comfortable with a cheap autoreading meter as there is less to go wrong.

Semiman


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## TigerF (Oct 27, 2011)

I have a DT 830B Digital Multimeter, on sale at Fry's Electronics for probably $4.00-5.00 or so, a couple of years ago. It looks almost identical to the Harbor Freight multimeter. I haven't had problems with any leads breaking or anything like that. It's fine for simple measurements. I use it to perform simple diagnostics on my car, as well as check battery voltages. It runs on a single 9V battery. Like others said, set it on the 20V scale to check battery voltages. It's worked for me, so far...


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## march.brown (Oct 27, 2011)

SemiMan said:


> Just because you can get an accurate voltage reading on one scale does not indicate that you can get accurate readings on all scales and all things you are reading. This has been my issue with cheap meters ... cheap switches and dials and flaky readings. I would certainly feel more comfortable with a cheap autoreading meter as there is less to go wrong.
> 
> Semiman


My cheapie meters are normally only used for measurements on my torch batteries ... I use the twenty volt DC range for Li-Ions and the two volt DC range for NiMh cells ... The resistance ranges also get used on fuses , bulbs etc ... I can trust the reading on the twenty volt DC range as it is checked against my five volt reference device.

I am perfectly happy with my meters and should they eventually fail , I will simply buy another ... I can take my five volt reference device to the shop and check the cheapie meter before I buy ... No problem ... The salespersons all seem very keen to see how their products perform.


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## xul (Oct 27, 2011)

It's not obvious but you can use a wall oven and a 4-1/2 digit DVM to measure the short circuit current capability of your residential panel. Mine came in at 10,800A. 

You can probably make any cheapie meter safer for mains work by putting a fuse in series with the meter with an interrupting current rating greater than your particular value. 

The RCA Voltohmyst, a VTVM, used this method. It had two fuses in series which didn't make sense until you looked at the parts list.


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## Flying Turtle (Oct 27, 2011)

I've also been using a Craftsman for a few years. I think I paid less than $20. They are often on sale and there is a large selection. Certainly good enough for voltage checks.

Geoff


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## samgab (Oct 27, 2011)

Here's something interesting:
I just received a DMMCHECK precision 5.000V voltage reference in the mail today.
I tested the Entry level Fluke 17B versus one of the old cheapies I had lying around. 
Here are the results:









So the cheap junkie one is more accurate (At 5 V) than the Fluke that I have been relying on!
Now I want to get a "PentaRef" so I can check the readings at different scales of DC Voltage.

Edit: I've adjusted the 17B now. The precision voltage reference is accurate, for those of eevblog who doubt:


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## xul (Oct 27, 2011)

samgab said:


> So the cheap junkie one is more accurate (At 5 V) than the Fluke that I have been relying on!


On average it shouldn't be but you'd have to check several meters of each kind to see how these two meters compare. 

Does 5.00 +/- 0.04 v pass spec on the Fluke? 
+/- 0.5% of 5v is .025v + 3 LSBs would give 4.98v + 3 LSBs. 
The Fluke might be out of spec by 1 LSB.


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## samgab (Oct 28, 2011)

xul said:


> On average it shouldn't be but you'd have to check several meters of each kind to see how these two meters compare.
> 
> Does 5.00 +/- 0.04 v pass spec on the Fluke?
> +/- 0.5% of 5v is .025v + 3 LSBs would give 4.98v + 3 LSBs.
> The Fluke might be out of spec by 1 LSB.



The rated accuracy spec for the Fluke 17B for DC Volts is .05% +3 counts Least Significant Digits.
So the spec for 5.00V would be (rounded) 4.95-5.06 V. So yes, it's within spec... Just. 
(4.98-3LSD is 4.95.
5.03+3LSD is 5.06.)
See @6m 18S of the video onwards for explanation of the LSD counts...


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## HKJ (Oct 28, 2011)

samgab said:


> The rated accuracy spec for the Fluke 17B for DC Volts is .05% +3 counts Least Significant Digits.
> So the spec for 5.00V would be (rounded) 4.95-5.06 V. So yes, it's within spec... Just.
> (4.98-3LSD is 4.95.
> 5.03+3LSD is 5.06.)



That is the reason to get a DMM with 6000 reading (Like the one I posted before). The + count is 10 times less significant when measuring on LiIon.
The better Fluke meters does also have 6000 count.


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## samgab (Oct 28, 2011)

HKJ said:


> That is the reason to get a DMM with 6000 reading (Like the one I posted before). The + count is 10 times less significant when measuring on LiIon.
> The better Fluke meters does also have 6000 count.



Yes... What a shame the chemistry isn't fully charged at 3.95V  I think a 6000 count is the way to go... Not necessarily more accurate, in percentage, but under 6V it has much better resolution.


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## march.brown (Oct 28, 2011)

xul said:


> On average it shouldn't be but you'd have to check several meters of each kind to see how these two meters compare.
> 
> Does 5.00 +/- 0.04 v pass spec on the Fluke?
> +/- 0.5% of 5v is .025v + 3 LSBs would give 4.98v + 3 LSBs.
> The Fluke might be out of spec by 1 LSB.


It would be nice to have an extra digit in the display ... 4.98V could be out by plus or minus five millivolts ... So the actual reading on a better meter display could be anywhere between 4.975V and 4.985V ... I can't justify spending more money just to get that degree of accuracy even though I would like it ... So I make do with being possibly up to five millivolts out as well as the 0.5% and the 3LSBs ... Luckily the Li-Ions have a small ammount of latitude and mine always come off the charger at less than 4.25V.

I also check that my cheapie meters read 5.00V when checked against my five volt reference device ... I've been lucky so far and my meters are reading within five millivolts ... That's great for meters that cost well below £5.
.


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## xul (Oct 28, 2011)

I couldn't do anything right yesterday.
+/- 0.5% of 4.96v is .025v + 3 LSBs is .03 so you'd have 4.96 + .03 + .03 would give 5.02v so this meter is within spec. It also means about 2/3rds of the meters sold would read 4.96 +/- .03.

In the video he, I think, showed +/- 1 mV and +/- 2 counts. This is not the same as +/- [1 mV + 2 counts], which I think is the correct statement. 
In the first statement the LSB or LSD error could cancel out the mV error. I don't think that happens.

I did find it surprising how the meters displayed resolution as the voltage was increased. I've never had an occasion to discover this.

If he heard me speak he'd say I have a thick American accent [because I had a hard time understanding him in some places].


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## Tommygun45 (Oct 28, 2011)

Goodness, thanks for all the replies guys. Again, I was not saying that I 'know' that my batteries are in great shape, but they are all fairly new and I really dont use my lights that much to be honest. They have never been totally drained, and I have never left them on the Pila for extended periods of time, just until the light turns green. 

That being said, this is the only application I have to use a multimeter. I was just kind of curious because of some strange behavior from the Pila. When I have two AW cells on there and one of them shows green, when I take it off the other one will switch to green as well. This happens each time I change cells on either side. If I put that cell that just turned green back on it will charge, sometimes for hours more. But other times its on my 16340's and I know they dont take long to charge, so it can be tricky. Having one of these things would just allow me to confirm that its in the proper voltage range. 

Ill order up one now and see how it goes. Ill try to find the one for ~16 off amazon. Thanks guys


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## samgab (Oct 29, 2011)

Cheap meters can be taken apart and adjusted using the trim pots if you have a precision reference to get source readings from:
It feels great to connect to a 5.000V source and see 5.00 on the display, or connect to a 1.0000 mA source and see 1.00 mA or 1000 μA. Good times.
Pix or it didn't happen:

























To the OP, good on you for ordering a DMM... you will find it invaluable as you get more into li-ion chemistry etc. It's really an essential item.

I think a few things to look for, even in relatively cheap DMMs:
* Ceramic HRC (High Rupture Capacity) fuses - not glass.
* Fused at both Amps and mA.
* Good input overload protection, such as PTC thermistors and MOVs.
* Quality test probes, with quality rated leads.
* Build quality/plastics quality/soldering.
* Good positive dial. Not "mushy".
* Clear readable display, at most angles of view.
* Avoid silly gimmicks like transistor test functions.


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## xul (Oct 29, 2011)

For accuracy, what is the smallest volt difference or percentage difference in batteries that is meaningful? Get a meter that reads 5x better than this.

For trends you only need ratio accuracy, not absolute accuracy.


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## march.brown (Oct 30, 2011)

If you can check your meter against a voltage reference device , you will see how far out your meter is reading ... You can then correct any other readings taken on that meter range to get the absolute value ... I had one meter that was reading 40 millivolts high on the 20 volt range when checked against my five volt reference ... If I deducted 40mV on a five volt reading then it became five volts ... For four volt readings , I deducted 32mV to give the corrected reading ... I never thought about taking the back off to adjust the potentiometer ... I must remember that for the future.

As my other cheapie meters were reading spot-on , I gave that meter to my Son-in-Law as he didn't need a high degree of accuracy.

It would be very nice to read Li-Ion voltages with an accuracy of one millivolt , but in all fairness if you can get it within 10mV it is perfectly adequate ... I know that my meters all read my reference as 5.00V ... When I check a Li-Ion at 4.20V , the actual voltage can be up to 10mV out (probably less) ... Because of the number of LCD digits on the meter , mine will only read to ten millivolt divisions ... An extra digit would add quite a bit to the price ... For the cost of these meter , their accuracy is amazing ... I check my meters against the reference quite regularly (just in case) ... It only takes a couple of minutes as the reference is always kept at room temperature.
.


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## moderator007 (Oct 30, 2011)

Since we are discuss adjusting cheap meters. I dont think I remember seeing A pot on my cheap harbor frieght DMM.
So has anybody attempted to try to adjust A HF DMM by changing resistors or installing a pot?
Or maybe even know which resistor affects the voltage reading. I have one out of three thats about .03v off.
I liked to see if I could correct it if possible.


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## xul (Oct 30, 2011)

Post the meter schematic or the numbers off the top of any chips inside. 

The trouble with cheap stuff is that it may drift with time or temperature or humidity even if you manage to get it to read exactly the true value at the moment.

That's another thing I learned from that video; determining your own calibration interval based on measurements over time.


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## samgab (Oct 30, 2011)

moderator007 said:


> Since we are discuss adjusting cheap meters. I dont think I remember seeing A pot on my cheap harbor frieght DMM.
> So has anybody attempted to try to adjust A HF DMM by changing resistors or installing a pot?
> Or maybe even know which resistor affects the voltage reading. I have one out of three thats about .03v off.
> I liked to see if I could correct it if possible.



I have opened up all of my cheap DMMs, and they all have trim pots. I don't have your Harbour Freight one, but I'd say that it almost certainly has at least 1 trim pot. Look very closely at the circuit board, sometimes they are quite small, just a little metal circle with a + cutout... Or post a link to a hi res photo of the circuit board. I'd be suprised if there was no trim pot at all. There should be some way for the factory to calibrate them... The high end meters have a software calibration function, but most low end meters just have potentiometers.


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## xul (Oct 30, 2011)

samgab said:


> I have opened up all of my cheap DMMs, and they all have trim pots. I don't have your Harbour Freight one, but I'd say that it almost certainly has at least 1 trim pot. Look very closely at the circuit board, sometimes they are quite small, just a little metal circle with a + cutout... Or post a link to a hi res photo of the circuit board. I'd be suprised if there was no trim pot at all. There should be some way for the factory to calibrate them... The high end meters have a software calibration function, but most low end meters just have potentiometers.


They might use PC track jumpers which are cut at the factory to get close enough. With cheap labor anything goes.


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## DFiorentino (Oct 30, 2011)

moderator007 said:


> Since we are discuss adjusting cheap meters. I dont think I remember seeing A pot on my cheap harbor frieght DMM.
> So has anybody attempted to try to adjust A HF DMM by changing resistors or installing a pot?
> Or maybe even know which resistor affects the voltage reading. I have one out of three thats about .03v off.
> I liked to see if I could correct it if possible.



My CEN-TECH HF cheapy does indeed have a pot. And I did indeed adjust it by about 5 (or less) degrees to regain 0.01VDC of accuracy. Adjustment seemed linear in the range of voltages I use it to measure with.

-DF


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## Mr Happy (Oct 30, 2011)

moderator007 said:


> Since we are discuss adjusting cheap meters. I dont think I remember seeing A pot on my cheap harbor frieght DMM.
> So has anybody attempted to try to adjust A HF DMM by changing resistors or installing a pot?
> Or maybe even know which resistor affects the voltage reading. I have one out of three thats about .03v off.
> I liked to see if I could correct it if possible.


On the Cen-Tech 90899 meter from Harbor Freight (the "$2.99 special"), the adjustment pot is on the right hand side about 1/3 way down from the top. It is raised off the circuit board on three legs. You can adjust it by making very tiny movements with a small flat blade screwdriver to match any DC voltage references you have. I just adjusted two of mine to align closely with some more accurate references. I only needed to turn the pot by half a gnat's whisker.

Be careful with this meter as the rotary range selection dial can be a bit temperamental. Give it a good few turns back and forth to clean the contacts before you try adjusting the meter. You really don't get gold plated quality with a $2.99 device.


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## moderator007 (Oct 30, 2011)

Thanks for all the replys.
I had the cover off one time for something, But I didn't ever see a trim pot. I wasn't really looking for it though.
I will go back and examine it a little closer tonight. Will post back what i find. Mr happy that is the meter I have the bad reading on.
I do know exactly what a trim pot looks like and does. No flame intended. Thanks again!


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## moderator007 (Oct 31, 2011)

Well, feel kind of silly. Opened it up and there it was as plain as day. Eactly where Mr Happy said it was.
I was expecting a small pot. But this one is quite large for a surface mount pot.
Its location on the board is kind of in the top right hand side. Its kind of stuck there all by itself away from all the main componets on the board. This is probably why I didn't see it the first time.
I did remember why I had the cover off the HF DMM, to change the battery.:thinking:
I did notice that the temperature played a part in what the reading was. I had one out in the cold garage. When I brought it in and started adjusting it would start to drift. So I let them all stabilize in temp then started adjusting.
Got all my HF DMM's tuned up last night. Thanks to all! :thumbsup:


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## pobox1475 (Oct 31, 2011)

Without reading closely through thread, does it mean my Harbor Freight meter will not be accurate enough for the Eneloops and AW's I use ?


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## moderator007 (Oct 31, 2011)

The HF DMM will be fine for those type measurments. Mine was reading .03 volts to low. 
Not that big of deal for batteries.
But it is best to adjust it with a voltage reference or agaisnt a known good meter.


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## Mr Happy (Oct 31, 2011)

All of my HF cheapo meters were reading close enough out of the package and didn't really need adjusting. For example they typically showed 5.01 V against a 5.000 V reference, but there is no guarantee that they will always be that way.

Over the weekend I discovered an interesting cheap voltage reference in a brand new super heavy duty 9 V battery. It was very close to 10.0 V, at one point reading 10.000 V on my accurate meter. I need to try a few other samples to see how common and consistent this is, or whether it was just a one off thing. (To clarify, the battery seems to be somewhere between 9.95 V and 10.05 V, which is not precise by any means but it might a good basis for a rough and ready test.)


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## moderator007 (Oct 31, 2011)

I have three HF DMM's that all were good but the one. The rest were within .01v and sometimes they were dead on. Temps may have played a part in the deference. But that one never read in better than .03v accuracy.

Any way I thought I upload a pic for all to see what and were the adjustable potentiometer is on the HF DMM.
When I google searched I never come across any info on this. So here it is. Clock wise reads more voltage, counter clock wise reads less voltage.


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## Mr Happy (Oct 31, 2011)

Well that's interesting. Apparently they are not all the same inside. This is what one of my meters looks like:






Does your meter have the transistor tester socket?


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## moderator007 (Oct 31, 2011)

Yes it does Mr Happy. Its just to the right of the fuse slighly under the red and black wires. You can make out the pins in the pic above. And on the HF coupon that I believe ran out today for a free one.
They list two different model numbers on the coupon.
I think one is new design and one old design. I do have both but neither look like yours.
One has a blue on and off switch while the other is yellow.
Update : checked the coupon says model# 90899 or 98025. And coupon still good until 11-17-2011.


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