Just how good or bad can a $1.78 DT-830B multimeter from AliExpress be?

[graybeard]

When I open the AliExpress app on my iPhone it starts by presenting me sale items for $1.99, and sometimes $1.78 with free 15 day shipping and free returns.  So a few weeks ago I opened the app and it offered me this DT-830B multimeter for $1.78.  So I decided to try it out.

This particular model does not have a continuity buzzer.
It uses a 9V battery.  Two tiny self taping screws, which are threaded into plastic bosses, hold the case together.  So I put fully charged 9V battery in and turned it on.
I first decided to measure the input characteristics that are not mentioned in the specifications.

The input resistance on all of the DCV ranges was 1 MegOhm, on the ACV ranges it was 3.9 MegOhms.

The measured resistance on the current ranges was:
200µA    1K
2mA        100 Ohms
20mA      10 Ohms
200mA     1.2 Ohms
10A          0.01 Ohms

The open circuit voltage reading on the diode and 200 Ohms resistance range was ~2.5V.   The remaining resistance ranges all had an open circuit voltage of ~0.26V.

The box claims the accuracy of the DCV readings is 0.5% ±2 digits which I would be happy with.  The pamphlet that cam in the box claims 2% ±3 digits which would be acceptable.  So I decided to check the accuracy with my PDVS2mini which I know once warmed up is accurate to ±10µV since I have check it with fully NIST traceable calibrated meters.   It turns out this kind of accuracy was extreme overkill.   The meter did not come close to meeting the 2% specification.  I checked near full scale and the readings were off be 19%.  This is 💩 accuracy.  You can see some of the measurements in the images below.

Now let's consider this meter's input protection.
The box claims all of the current ranges (except 10A) are protected by a 200mA fuse.  The pamphlet and case both claim a 500mA/250V fuse.  In fact if you looks and the board inside you will see that there is a place reserved for a fuse, but there is no fuse there.  This is 💩.
If you look at board you will see that there are spots for some rudimentary protection, but they are unpopulated, no PTC, no clamping diodes (D2 & D3), no BJT Q1.  Again this is 💩, although I do give them credit for not claiming BS CAT ratings.

The 10 Amp current range shunt resistor is a 0603 0.01 Ohm chip next to the input terminals.  You can see the holes on the board for a larger shunt, but that is not used.  If you assume the 0603 resistor is a quality part (unlikely) then it's maximum rating would be 100mW,  This means the maximum current the resistor should see it 3.1 Amps, not 10 Amps.  It is c.

If you look at the right side of the circuit board.  You can see the leads that go to the 9V battery connector.   There is enough bare lead that they could easily short.

I asked for a refund and AliExpress gave me a $3.86 instant refund for a meter I paid $1.78 for.  The meter is 💩, but I am happy I don't have to pay for it!

Chris

P.S. I love my PDVS2mini.  I use it all the time to check my equipment accuracy.

[NoisyBoy]

It looks exactly like a Harbor Freight DMM I actually paid for about 15 years ago, before they became free with coupons and added a battery test function.

On mine, there is actually a single pot for adjusting DC accuracy, plus a cheap glass fuse. They clearly have managed to further decontent the meter to cut cost. With adjustment, it is barely able to stay within the 2% spec for DC voltage.

I notice the low battery icon is on on your meter, to be fair, low battery can make any DMM produce erroneous reading. You said your battery is a fully charged battery, have you tried a fresh 9V alkaline battery in it to see if the reading is the same?

You should show the probes, if you see the actual wires in it, I don’t see how it can withstand 10A for any period of time.  You can also effortlessly pull the probe off the wires.

While I will never pay for another meter like it, perhaps its price point is enabling a lot of people in less affluent countries to get started in electronics as long as they don’t try to use it on high voltage or current circuits.

[graybeard]

I checked the battery before and after with my ZTS battery tester.  The battery was good!

[J-R]

These have been around for ~25 years at this point.  I have a handful I got from Harbor Freight back in the 90s.  The marketing folks loved them.  Free with coupon, free with every purchase over $50, buy one get one free, whatever.

There were some other permutations, with slightly different feature sets.  I remember having some red, yellow and black ones over the decades. Of course back then they were all through-hole components, none of this surface-mount rubbish.

Even then they were toys, a trinket...

[wraper]

Shunt looks 1206, not 0603.

[robert.rozee]

what amazes me, is why they still include a transistor tester - who on earth is going to make use of that feature these days?! omitting the transistor testing function would also be an obvious way to cut a few cents off the manufacturing cost.

the fact that the 'low battery' warning showed throughout is a sure sign that the meter being tested was either faulty, or the PCB was assembled for use with a 12 volt (A23 size) battery.


cheers,
rob   :-)

[RoGeorge]

The battery indicator says the battery is not good.  If the battery is a new 9V alkaline, then maybe the DMM you are testing is defective, therefore comparing accuracy is irrelevant as long as the low battery sign is there.

I have had one that sits in the car.  Worked very well so far, mostly as a voltmeter, used it only rarely, once in a year or so.  Mine was in specs, I bet probably still is.  It doesn't measure well with a low battery.

For current measuring, I guess the probe themselves will melt at 10A. 
Might survive for a couple of seconds if you measure quick, though, never tried it at 10A.  The DMM doesn't look safe for high voltage/high current measurements.  Not recommended for electricians, but good enough for low voltage/low power, or for a beginner that wants to step into electronics for cheap and will only work with microcontrollers and/or battery powered circuits.

DT-830B can also make a good panel meter, it's cheap enough to embed it definitively together with other projects.

For the price, I'll say it's a great DMM. 

[exe]

Love those, a similar device was my first DMM >20years ago. Back then we were discussing which meter is better: digital or analog? I was into digits (and still is), my friend who was much older was into analog gauges.

[mendip_discovery]

Seen many of these over the years. Some are good, some are rubbish.

Seem them in the Car parts shops etc.

I have one in the shed, it was handy for checking battery voltages and for use as a continuity meter.

I refuse to use it for current or mains voltages due to the the state of the test leads.

You might have bought a meter designed as a knockoff of the ones we normally see. Same meter just with a few parts missing to get the price down.

[Fungus]

I've got one somewhere, doesn't everybody?

They usually measure OK and the displays are really clear. Really easy to zap though and the leads are rubbish (hint: put some hot glue in the top of the probe handle (where the wire goes in) to stop the wire spinning around inside and breaking).

If yours has that much measurement error it's probably a production defect. Don't give up on them. 



PS: At least try and get one with a beeper.

[Gyro]

What on earth happened to that track to the +ve battery connection. It looks as if somebody suddenly forgot how to use the PCB package or resorted to Paint! 

[Miti]

I absolutely refuse to touch those HF type multimeters. As a general purpose multimeter, one in the car just in case, one on each shelf, etc., I’m using Innova 3310. They used to be 9.99$ at Canadian Tire but not anymore. I found some on Kijiji and at garage sales in the past but they are gone. Much better than HF in every aspect. For the new -er auto ranging 3320 model, CT wants an arm and a leg.

[Fungus]

What on earth happened to that track to the +ve battery connection. It looks as if somebody suddenly forgot how to use the PCB package or resorted to Paint! 

At least they put in a PCB slot to prevent arcing between the input terminals:

[robert.rozee]

the manufacturers have certainly applied all their 'skills' to the design   

it would be an interesting exercise for Dave to create a multimeter design similar to the DT-830B, but done right. ie, a bottom-of-the-market budget DMM, very similar in appearance and function to the DT-830B, but using good design practice and with at least a modicum of safety features - that is safe for mains voltages.

are you there Dave?


cheers,
rob   :-)

[mendip_discovery]

If Dave was to do that as a thinking exercise, I am sure that the factories would start churning them out.

Don't just assume the chinese board designers are stupid. They are just doing it as cheap as possible so safety takes a back seat.

[Fungus]

it would be an interesting exercise for Dave to create a multimeter design similar to the DT-830B, but done right.

That meter's PCB already has footprints for clamping diodes, a fuse, etc. 

Don't just assume the chinese board designers are stupid.

Nope.

Designing something as cheap as possible is just as difficult than "doing it right, no expense spared".

The squiggle around the red wire is probably Chinese for "LOL!" or something like that.   

[Zenith]

I suppose those meters are OKish for quick checks on low voltages or for continuity, (shame about the buzzer) all assuming you rarely use a DMM and so don't want to spend much at all on one.

You of course have the sense not to take it anywhere near mains voltages or anything like that.

[RoGeorge]

I doubt anybody can do a better DMM for the final price of $1.78, and for that price the DT-830B is probably the best DMM on this Earth.  Complaining about such a DMM is not withstanding at high voltage or high current looks to me like complaining about why a bicycle doesn't have airbags, or at least a reinforced inside cage for the bicycle pilot, like stunt cars have.

Talking about how this one is not like other DMMs that cost 10...500 times more doesn't make sense.  Try finding something similar to compare against.

Did any of you know any better DMM for less than $2?

[Fungus]

You of course have the sense not to take it anywhere near mains voltages or anything like that.

Millions of people do it and live... 

[NoisyBoy]

Can’t argue with that price point. HF give them away to get people into the store, at this price with free shipping, they ought to lose money even if they get the DMM for free.

For some of the meters I have, I do notice voltage readings would be off if they sit there for months, a disassembly with a cleaning around the selector tracks would clear it up.

[Zenith]

It's the same as a lot of other things such as power tools, say angle grinders.

You could buy them for €14. Not very powerful and they didn't last long, switches broke and gears stripped. But for a one off job, or you wondered what it could do and how much you'd use one, fine. Arguably they were dangerous.

You can buy mid priced ones , €40 plus or minus, which put up with a lot more use and abuse.

You can spend hundreds on top end Makita etc. Lots of power, low vibration, full spares availability and they last for years. I'm not sure it makes sense to buy those, unless you are going to give an angle grinder daily use.

From my experience I wouldn't recommend anyone should buy the very cheapest, although I can see why people buy them.

[Zenith]

You of course have the sense not to take it anywhere near mains voltages or anything like that.

Millions of people do it and live... 

Very few deaths are caused by mains shocks.

It's the bang and the flash when these things arc over internally that some people have found disturbing.

[Fungus]

Did any of you know any better DMM for less than $2?

I'm not sure where I could get one at that price.

On a related note: What's the best DT830?

Maybe this one: https://www.aliexpress.com/item/1005005195899615.html

It has ABS plastic, backlight, buzzer... doesn't say anything about internal fuses though.

Edit: Found a thread, there's no fuses.

what amazes me, is why they still include a transistor tester - who on earth is going to make use of that feature these days?!

That Aneng advert ^ shows a white LED plugged into the transistor tester and lit up. 

[Fungus]

Big Clive's other "trashy meter" with fuses and stuff is actually quite expensive:

https://www.aliexpress.com/item/1005005253798134.html

[factory]

This one on the right (DURATOOL D03047) was bought from CPC/Farnell in the UK in 2019 for £3.28+tax, it has a separate board for the jacks and a 5A fuse for the 5A range, it replaced an old faulty Hilka branded version which had no fuse for the 10A range.



David