new candidate for world's worst DMM - Page 1
Forum section: electronics / testgear

author: Pfriemler
author_rank: Regular Contributor
timestamp: September 08, 2023, 02:12:23 pm
content: ongoing from this old thread:https://www.eevblog.com/forum/testgear/world_s-worst-dmm/25/and some other cheapos I think I got a new version. "They" call it DT830B.3 (see pics below).Unlike Fungus, I did nothave to buy three at once, just grabbed it for 4,49 Euros from the local dutch "ACTION" market (and will return it, maybe).They sell it as "VARO VAR10076/23". Do not look and search on the web site, the photes are not up to date.So, here's another famous DT830 clone:First: it has a seperate power switch. Battery is included, so it works out of the box.Connected to my AD584, readings are 2.49, 4.98, 7.47 and 9.97 volts. Not that bad.What it lacks on the voltage side, it gives up to the currents: 98 mA are read as 100.x. OK...Resistor measurements are usable. Tips together, I get 0.3 ohms.hfe ...... well, it works, compared to my GM328.and now ... drums please ... the 5A socket: 1 A becomes 1,51 A. WTF? ... 5 amps are read as 7,56. 50% error.Time to get inside:This is almost aknown view inside. The very poor sockets, the ridiculous insulation spaces between them.Unlike other versions, we have fuses! SMD fuses, melted to the pcb, rendering the device useless in case they are blown up.The 5A shunt is a 0.01 smd one, the second footprint is not populated. No idea why we have the 50% error, but here's an opportunity to fix it.But now, Ladies and Gentlemen, we get to the best: The battery checker.See the printing on the front side. 4 mA @ 1.5 volts, 20 mA @9 volts. Looks like a 360 ohms load inside, and it is. Should be vice versa - some mA with 9 V blocks and 20 mA with 1.5V cells, but hoiw to get it without separate switch positions? But if you expect a voltage reading here from the loaded battery - NO, IT'S THE CURRENT!

author: wraper
author_rank: Unknown
timestamp: September 08, 2023, 02:37:58 pm
content: It actually has fuses inside. So in no way it beats usual 830 type clones.

author: antenna
author_rank: Frequent Contributor
timestamp: September 08, 2023, 02:43:46 pm
content: Makes a good RF field strength meter

author: Pfriemler
author_rank: Regular Contributor
timestamp: September 08, 2023, 02:44:25 pm
content: Just read that the battery tester is not new: the linked one above has a 42 ohms load and reads current, too.I forgot a detail: open tip voltage in 200 ohms resistor range is 2.95 volts, and a white LED is lit. Applause!The main reason why I got this: I had to examine one before I suggest some people to buy this. A very poor DMM is better than no DMM in some situations. Despites the 5A error and the rather useless battery load current it does the job when telling good from bad batteries, searching for a shortened or broken cable or even check the mains voltage. The leads are cheapos as well, but without any obvious life danger.

author: Fungus
author_rank: Super Contributor
timestamp: September 08, 2023, 02:45:37 pm
content: Quote from: Pfriemler on September 08, 2023, 02:12:23 pmSo... you got a broken one?Quote from: Pfriemler on September 08, 2023, 02:12:23 pmTesting batteries under a small load is the correct way to do it. OK, they did it a bit strangely (firmware space isverylimited in those chips) but if the instructions are printed on the case then I don't see a problem.

author: Fungus
author_rank: Super Contributor
timestamp: September 08, 2023, 02:50:28 pm
content: Quote from: Pfriemler on September 08, 2023, 02:44:25 pmI'm still happy with my "Big Clive" meters. They'resmalland cute and do the job.Most readings done with them are 5V and continuity at Arduino club. I can fit one of thoseanda Zeeweii oscilloscope in the same space as a "real" meter in my case.

author: tszaboo
author_rank: Super Contributor
timestamp: September 08, 2023, 02:59:14 pm
content: Quote from: wraper on September 08, 2023, 02:37:58 pmI was going to say this. Plus it has a SMD shunt instead of a (probably) a piece of nail bent and soldered into the board.Having the on/off witch is strange though.

author: Pfriemler
author_rank: Regular Contributor
timestamp: September 08, 2023, 03:06:22 pm
content: Quote from: antenna on September 08, 2023, 02:43:46 pmOMG ... looks like a similar DMM! Where did you get that? I searched a while for a similar, but found none.Quote from: Fungus on September 08, 2023, 02:45:37 pmNo affort to get back to the store and replace it. Maybe I should do that.QuoteOnce you got it, you only have to remember to good and poor current values... Of course a load is needed to get reasonable readings with batteries, but most other DMM combine the load with the voltage reading. They had to clone not the 20 mA, but the 20 V range in the firmware. Maybe only a typoQuote from: Fungus on September 08, 2023, 02:50:28 pmeven more space on the bench:

author: Fungus
author_rank: Super Contributor
timestamp: September 08, 2023, 03:13:41 pm
content: Quote from: Pfriemler on September 08, 2023, 03:06:22 pmI've got one of those somewhere. They're smaller but I really hate the leads (non-replaceable and they fill like they are going to break every time I stow them) and the non-standard 12v battery.

author: Veteran68
author_rank: Frequent Contributor
timestamp: September 08, 2023, 04:25:39 pm
content: The$7 Harbor Freight DT830 DMM(that they used to give away for free) has the same on/off switch and battery tester. I've had a few of these.I also bought three of Big Clive's trashy meters (the Duratool D03047) which have much better internals than these base DT830 models plus a nifty yellow holster. However no on/off switch nor battery tester.