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