Just how good or bad can a $1.78 DT-830B multimeter from AliExpress be? - Page 1
Forum section: electronics / testgear

author: graybeard
author_rank: Frequent Contributor
timestamp: March 05, 2023, 04:59:20 am
content: 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 methis DT-830B multimeterfor $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 1K2mA 100 Ohms20mA 10 Ohms200mA 1.2 Ohms10A 0.01 OhmsThe 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 myPDVS2miniwhich 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!ChrisP.S. I love myPDVS2mini. I use it all the time to check my equipment accuracy.

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: March 05, 2023, 05:39:27 am
content: 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.

author: graybeard
author_rank: Frequent Contributor
timestamp: March 05, 2023, 05:51:44 am
content: I checked the battery before and after with my ZTS battery tester. The battery was good!

author: J-R
author_rank: Super Contributor
timestamp: March 05, 2023, 08:21:32 am
content: 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...

author: wraper
author_rank: Unknown
timestamp: March 05, 2023, 08:29:59 am
content: Shunt looks 1206, not 0603.

author: robert.rozee
author_rank: Frequent Contributor
timestamp: March 05, 2023, 08:40:06 am
content: 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 :-)

author: RoGeorge
author_rank: Super Contributor
timestamp: March 05, 2023, 08:46:47 am
content: 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.

author: exe
author_rank: Unknown
timestamp: March 05, 2023, 08:58:58 am
content: 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.

author: mendip_discovery
author_rank: Super Contributor
timestamp: March 05, 2023, 09:39:45 am
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2023, 10:22:30 am
content: 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.

author: Gyro
author_rank: Super Contributor
timestamp: March 05, 2023, 11:27:04 am
content: 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!

author: Miti
author_rank: Super Contributor
timestamp: March 05, 2023, 12:04:41 pm
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2023, 01:54:50 pm
content: Quote from: Gyro on March 05, 2023, 11:27:04 amAt least they put in a PCB slot to prevent arcing between the input terminals:

author: robert.rozee
author_rank: Frequent Contributor
timestamp: March 05, 2023, 02:08:15 pm
content: the manufacturers have certainly applied all their 'skills' to the designit would be an interesting exercise for Dave to create a multimeter design similar to the DT-830B, but doneright. 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 :-)

author: mendip_discovery
author_rank: Super Contributor
timestamp: March 05, 2023, 02:17:33 pm
content: 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.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2023, 02:37:51 pm
content: Quote from: robert.rozee on March 05, 2023, 02:08:15 pmThat meter's PCB already has footprints for clamping diodes, a fuse, etc.Quote from: mendip_discovery on March 05, 2023, 02:17:33 pmNope.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.

author: Zenith
author_rank: Frequent Contributor
timestamp: March 05, 2023, 02:53:16 pm
content: 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.

author: RoGeorge
author_rank: Super Contributor
timestamp: March 05, 2023, 02:54:06 pm
content: 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?

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2023, 03:44:21 pm
content: Quote from: Zenith on March 05, 2023, 02:53:16 pmMillions of people do it and live...

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: March 05, 2023, 03:50:13 pm
content: 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.

author: Zenith
author_rank: Frequent Contributor
timestamp: March 05, 2023, 03:53:21 pm
content: 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.

author: Zenith
author_rank: Frequent Contributor
timestamp: March 05, 2023, 03:58:23 pm
content: Quote from: Fungus on March 05, 2023, 03:44:21 pmVery 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.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2023, 04:26:16 pm
content: Quote from: RoGeorge on March 05, 2023, 02:54:06 pmI'm not sure where I could get one at that price.On a related note: What's thebestDT830?Maybe this one:https://www.aliexpress.com/item/1005005195899615.htmlIt has ABS plastic, backlight, buzzer... doesn't say anything about internal fuses though.Edit:Found a thread, there's no fuses.Quote from: robert.rozee on March 05, 2023, 08:40:06 amThat Aneng advert ^ shows a white LED plugged into the transistor tester and lit up.

author: Fungus
author_rank: Super Contributor
timestamp: March 05, 2023, 04:49:49 pm
content: Big Clive's other "trashy meter" with fuses and stuff is actually quite expensive:https://www.aliexpress.com/item/1005005253798134.html

author: factory
author_rank: Super Contributor
timestamp: March 05, 2023, 08:09:15 pm
content: 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

author: james_s
author_rank: Super Contributor
timestamp: March 05, 2023, 08:26:53 pm
content: I've kept one of the free Harbor Freight meters in my car for years, it comes in handy every once in a while. They're fine for kids tinkering too, much better than anything I had access to when I was a kid, a digital meter like that probably would have cost $100 in the early 80s.

author: Grandchuck
author_rank: Super Contributor
timestamp: March 05, 2023, 08:34:54 pm
content: Hickok DMM, 1970, $395.00

author: J-R
author_rank: Super Contributor
timestamp: March 05, 2023, 09:26:27 pm
content: Of course these cost more than $1.78 to make and far more than that to ship; there is no free lunch. The money comes from elsewhere.

author: Zenith
author_rank: Frequent Contributor
timestamp: March 05, 2023, 09:27:31 pm
content: Are they any worse than the Japanese 1000 Ohm per volt analogue multimeters sold in the late 60s? I'm sure many of us bought and loved those. I think they did have a proper wafer switch. Mine does but it's a deluxe 30,000 Ohm/V version. It does have a separate 1.2KV input. I've never tried it and never will. Proper people would have had an AVO or Simpson, and wouldn't be seen dead with such a thing.I believe these DMMs do their switch thing by contacting lands on the circuit board. They are value engineered. Copper dust builds up and causes problems, such as BANG!!!. Low voltages, continuity and it's silly to expect much else for the price.

author: Zenith
author_rank: Frequent Contributor
timestamp: March 05, 2023, 09:32:56 pm
content: Quote from: J-R on March 05, 2023, 09:26:27 pmThe shipping comes from an international postal agreement which has gone on for years and which the Chinese take more than full advantage of. Of course it has to be paid for.

author: Gyro
author_rank: Super Contributor
timestamp: March 05, 2023, 10:09:07 pm
content: Quote from: Zenith on March 05, 2023, 09:27:31 pmMost DMMs do these days, apart from some(?) Flukes.EDIT: Check out some of Joe Smith's DMM robustness tests. The Agilents / Keysights are quite entertaining on switch wear!https://www.youtube.com/channel/UCsK99WXk9VhcghnAauTBsbg/videos

author: David Aurora
author_rank: Frequent Contributor
timestamp: March 05, 2023, 11:06:05 pm
content: I look forward to seeing these in the next Jaycar catalogue for $20 each

author: Fungus
author_rank: Super Contributor
timestamp: March 06, 2023, 04:22:58 am
content: Quote from: Fungus on March 05, 2023, 04:26:16 pmLooking around, it might be this one:Info:https://lygte-info.dk/review/DMMDT-830D%20UK.htmlAliexpress:https://www.aliexpress.com/item/1005005161813621.html

author: NoisyBoy
author_rank: Frequent Contributor
timestamp: March 06, 2023, 05:25:43 am
content: Since the 10A range is unfused with only a shunt, I wonder what would happen if it goes beyond 10A? In the case of the HF meters, I afraid the probe wiring may act as the fuse, which can get ugly.The HF meters in the US is even more capable than the DT-830D+, as it can measure up to 750V AC, and 1000V DC! If one is brave enough to try it with the provided probes.

author: Fungus
author_rank: Super Contributor
timestamp: March 08, 2023, 07:46:19 pm
content: I've been trying to find Big Clive's other trashy meter but it's not easy to get hold of at a reasonable price. If I lived in the UK I could get one but bot here in Spain. :-(Farnell sells them for about $4 but I have to pay 15 Euros shipping. Maybe I could buy a dozen and flip them on eBay for a profit, keep one or two for myself.https://es.farnell.com/duratool/d03047/multimeter-digital/dp/3498310

author: factory
author_rank: Super Contributor
timestamp: March 08, 2023, 08:13:18 pm
content: Quote from: NoisyBoy on March 06, 2023, 05:25:43 amOr just make your own sticker up for it, example below from the TEA thread;Quote from: Brumby on July 23, 2018, 04:23:13 amDavid

author: graybeard
author_rank: Frequent Contributor
timestamp: March 10, 2023, 08:54:15 pm
content: Quote from: J-R on March 05, 2023, 09:26:27 pmIt seems to be some sort of loss leader on the AliExpress iPhone app. I do not see these deals on the web site. You have to choose 3-10 of these "special" items and they claim you get free shipping. Where I live I pay 10.5% sales tax, but Aliexpress adds about 18% for the tax. I suspect some of that "tax" amount goes to cover the shipping.When I bought the meter it was $1.78, but most times the offers are for $1.99, $2.99, or $3.99. If you look at an image from the iPhone app today you can see the meter is $1.99. I bought one of the $1.99 AppleWatch chargers for my wife and it works great.The meter I bought was defective, it shows a low battery all the time. But you may get lucky and get a good one. I have made for of these orders and "returned" three of the items as not described or defective. Each time I am given a refund within a few minutes of requesting it. The refunds are for the full price, bot the "sale price." Look at the refund I got for the meter. I paid approximately $2.14 with "tax" and was refunded $3.86, more than I paid.

author: Paul T
author_rank: Regular Contributor
timestamp: September 02, 2024, 02:33:25 pm
content: The variant of this meter shown in the lead post can be made adjustable for calibration. R8 is a 1K resistor. By replacing it with a resistance network that achieves a range around 1k, you can fine tune it while the leads are attached to a precision DC voltage source. For instance, a 900 ohm resistor in series with a 200 ohm potentiometer. I chose to use a 1.5K (18B) fixed resistor in the R8 spot, and a 5K micro pot in the empty space beside it, because it was handy and produced a professional result. When the pot is around 3K in || with 1.5K, 1K is produced.

author: Paul T
author_rank: Regular Contributor
timestamp: September 02, 2024, 03:18:58 pm
content: I took the time to add calibration so I could be precise with voltage readings for my 4-wire conversion.By adding a powerbank charge board, tested good lithium cell from a e-waste GPS unit, and a LM317 constant current source set to 100mA, I am now able to make quick 4-wire checks on any number of things. I have usb attachments to test cables, prong probes for PCBs and so on. The only feature I disabled was 10A mode. The main unit functions on the 9V battery as usual.The attachment shows checking a precision 100 milliohm resistor. I just have to multiply the mV voltage reading by 10 to determine milliohms.My point is these are not serious devices, but cheap enough to make inexpensive useful tools out of... so they are of some value. All together I may have spent $3 on the meter and consumables, nothing else required a purchase except the test clips to make a 4-wire tester. This meter and many others like it have plenty of room inside for extra circuitry for your application.