AN8008 US $19, 9999count, 1uV, 0.01uA, 0.01Ohm, 1pF resolution meter

[floobydust]

Hi, 2 questions

Can we access readings in UART?

No. The UART pins are not bonded out on the die. You can look with a scope for signal but people removed the chip glue and no wire connected inside
Be careful - Battery(-) is not multimeter input COM(-) and shorting those will blow the IC.

Can it be powered from li-ion battery 10440, ie 3.7v and a dummy cell?

Operating voltage spec is to 3.6V max. So I would add an LDO with 3.6V output to work with 3.7-4.2V input.
The LCD contrast might go too dark with higher VCC, it can be changed in EEPROM.

[chinhnguyen]

Hi. I just bought this DMM, I just added a few decoupling capacitors to it . But I notice a problem: it seems like this DMM can't measure the continuity of the diode right?
because current always flows from one direction, but I test the diode with the continuity function and it doesn't work in both directions.
if I use the diode function to test its still works. Is that a problem with this dmm or are dmm is the same?

[wasedadoc]

Continuity mode is for checking if the resistance between two points is a low value.  A diode even in forward mode acts like a higher value resistor to the multimeter.  If the diode reads ok in diode mode and the meter shows close to zero when the probes are joined in continuity mode there is nothing to worry about.

[floobydust]

In continuity mode (99.99Ω range), AN8008 test voltage is about 1.0V and test current 0.4mA
Diode 0.6V corresponds to around 1k6Ω so nothing is displayed. Below about 49.9Ω has 19mV across it then the beeper activates. So the meter is working normally.

[Dave Wise]

Apologies if this has been discussed.  Is the continuity test fast like the early Fluke handhelds that did it in hardware, or slow and IMO useless?

[Electro Fan]

Apologies if this has been discussed.  Is the continuity test fast like the early Fluke handhelds that did it in hardware, or slow and IMO useless?

Not super fast, not as sensitive and as fast as a Fluke 179 or a Brymen 789 but fast enough unless continuity is the only thing or the primary thing you are measuring.  What it's good at is supporting basic DMM functions in a small package and measuring reasonably accurately in the millivolt and milliamp range - and even down to hundreds of microamps. It isn't going to compete with a Keysight bench meter but it's surprisingly good for ~$30.  If someone wanted to get started with two meters to simultaneously measure low voltage and low current and didn't need industrial strength durability, it would be hard to find a better way to get this done with better accuracy for $60.  If you want industrial strength or measure high voltage it's not the right meter.  For entry level low voltage electronics it's a good deal.

Edit:  after re-reading my post I was concerned that maybe I overstated the voltage accuracy.  I just did some measurements with an old (not recently calibrated) DMMCheck reference from voltagestandard.com set for 2.0840V.  Nothing was warmed up for more than a few minutes but this is consistent with what I've seen over the years:  Fluke 179 2.047V, Aneng 8008 2.048V, Keysight 34465A 2.04824V.  The Aneng 8008 is pretty neat.

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Edit:  per Fungus' post just below, here is a video showing a DT9205A - looks like a potential dedicated continuity tester 

[Fungus]

Apologies if this has been discussed.  Is the continuity test fast like the early Fluke handhelds that did it in hardware, or slow and IMO useless?

Fast enough to not be in the "slow and useless" category.

If you want fastest possible continuity then an AN9205A is the one to get. Nothing is faster, at any price.
. It also has a really bright LED on the front that lights up for continuity.

For $8 you can afford to own one just for that. :-)

(I've considered pulling the PCB out of one and making a dedicated continuity tester in a 3D printed box but I never get around to it...)