Cheapest multimeter ever! - Page 1
Forum section: electronics / general

author: richardbrouwer1
author_rank: Newbie
timestamp: April 06, 2014, 05:15:40 pm
content: Hi guys! Found this on eBay, can't believe they produce it for this price and ship it for free!http://pages.ebay.com/link/?nav=item.view&id=161248077469

author: mrflibble
author_rank: Super Contributor
timestamp: April 06, 2014, 05:29:05 pm
content: What? $5? That's highway robbery! They usually go for less than that.One random example:http://www.ebay.com/itm/New-LCD-Digital-Voltmeter-Ammeter-Ohm-Multimeter-DT830-/400579128145?pt=US_Battery_Testers&hash=item5d44606b51

author: nanofrog
author_rank: Super Contributor
timestamp: April 06, 2014, 06:01:22 pm
content: Seen companies here in the US, namely Harbor Freight, give them away for free (i.e. perk for spending X amount of money in their store).

author: Neilm
author_rank: Super Contributor
timestamp: April 06, 2014, 06:21:48 pm
content: Interesting - I couldn't make out the rating so I did a quick search. The user guide I found says it was designed for 600V CAT I. I note that there are warnings in the User guide I found not to connect to mains. A quick glance through the manual, it might actually comply with IEC61010. <gasp>

author: Jarrod Roberson
author_rank: Regular Contributor
timestamp: April 06, 2014, 06:51:51 pm
content: transistor tester is a dead give away! glorified battery tester at best!

author: mrflibble
author_rank: Super Contributor
timestamp: April 06, 2014, 07:34:28 pm
content: I have one of those. Still a pretty old one with a dip chippie instead of the die with goop. And it's actually sortof decent for generic low voltage use and simple stuff. I wouldn't dream of using it on mains power though... Quick check of resistor values and DC power rails, yes. Precision, no. CAT rating, best ignore what's written on the box.

author: 128er
author_rank: Regular Contributor
timestamp: April 06, 2014, 07:53:22 pm
content: And here is the teardown of this famous DMM. First class build quality, with serial number and all what you can imagine. The flux capacitor of course is optionalNote the leads. Finest 0,25 mm² (or less) to handle 10A for current measurement.Datecode "4596", yeah - vintage. But still a decent meter

author: richardbrouwer1
author_rank: Newbie
timestamp: April 06, 2014, 09:27:39 pm
content: These are just the worst, had a sneek peek in a 10$ one and I was scared. Absolutly tiny and thin input rails. Guess they use them as a fuseIt had the most cruddy screen but it did work!(for a while)

author: 128er
author_rank: Regular Contributor
timestamp: April 06, 2014, 09:52:20 pm
content: So crappy the meter from my pictures is. The screen is not as bad, as the meter itself. It has a wide viewangle. Direct Sunlight isnt a problem also.But, hmm, i used this thing many years, till i got my agilent DMM. And once you have a good one, you will never use something like this. So - dont turn it on, toss it away

author: GabYoung92
author_rank: Regular Contributor
timestamp: April 06, 2014, 10:29:36 pm
content: what about $4.95 retail?...http://www.jaycar.com.au/productView.asp?ID=QM1502

author: wraper
author_rank: Unknown
timestamp: April 09, 2014, 04:45:28 pm
content: Quote from: 128er on April 06, 2014, 09:52:20 pmYour multimeter is old good variant of 830. New ones have two times smaller PCB which just barely covers switch and LCD zebra strip. Like on this picture (I have seen worse). They even make PCB out of two parts to skimp costs.

author: ablacon64
author_rank: Frequent Contributor
timestamp: April 09, 2014, 04:55:22 pm
content: I have one! Under a different brand called Minipa, Model ET-1001, it cost me 19 Reais (about 7 US dollars) 12 years ago (and it still uses the same probes!).

author: retiredcaps
author_rank: Super Contributor
timestamp: April 09, 2014, 05:15:24 pm
content: Quote from: wraper on April 09, 2014, 04:45:28 pmIt looks like the input jacks pcb is cut out from the main pcb (just under the pot) and then held together by 3 blobs of solder.

author: BravoV
author_rank: Super Contributor
timestamp: April 09, 2014, 05:19:29 pm
content: This 830 variant like these only cost about US$ 3 at street price here, and that even came with the 9V battery.

author: Refrigerator
author_rank: Super Contributor
timestamp: April 09, 2014, 05:51:21 pm
content: Talking about cheap meters, there is one called UT-136b, some say it's the best bang for buck meter out there.

author: Dajgoro
author_rank: Frequent Contributor
timestamp: April 09, 2014, 06:30:08 pm
content: What about this:http://www.ebay.com/itm/New-Electric-AC-DC-OHM-Voltmeter-Ammeter-Multimeter-Multi-Tester-MF-110A-/261375882881?pt=LH_DefaultDomain_0&hash=item3cdb377681I ordered it for a friend, but it never arrived...

author: 128er
author_rank: Regular Contributor
timestamp: April 09, 2014, 07:33:07 pm
content: Quote from: Dajgoro on April 09, 2014, 06:30:08 pmHm, is that good or bad?I totaly forgot this one from my crapcollection. 50x95x25 mm. Even with functiongenerator (squarewave), whoohooRuns from a 12V, A23 battery.PCB quality? There are far worse things on the market...

author: retiredcaps
author_rank: Super Contributor
timestamp: April 09, 2014, 07:58:56 pm
content: Quote from: 128er on April 09, 2014, 07:33:07 pmRebranded Uni-Thttp://www.uni-trend.com/UT20B.html

author: Suffer1981de
author_rank: Contributor
timestamp: April 09, 2014, 08:55:26 pm
content: I've got the same multimeter as the TO. Stylish yellow.Mine has even a shielding! The Fuse says F0,2A. And the sticker on the back says "Proven Safety" in german. Got it out of an High School here in Germany. Actually got 2 of them ;-)

author: ablacon64
author_rank: Frequent Contributor
timestamp: April 09, 2014, 09:48:41 pm
content: I can't resist, gotta show you this beauty! BTW I don't want to sell the probes, don't bother to ask!

author: wraper
author_rank: Unknown
timestamp: April 09, 2014, 10:32:45 pm
content: Here is my Mastech M830B. Won it on electronics contest when I was 13. Date code on the pcb says june 97, Got it somewhere on spring 98. Didn't get rid of it because of a nostalgic feelings. Forgot to take picture of the back cover, it even has shielding over almost the whole PCB. Just noticed that it even has a guard trace around the integrator parts, wow.

author: electronics man
author_rank: Frequent Contributor
timestamp: April 19, 2014, 10:02:11 pm
content: I can't believe the amazing quality of that thing they put a fuse in it

author: G0HZU
author_rank: Super Contributor
timestamp: April 19, 2014, 11:46:45 pm
content: The cheapest 'new' meter I bought was this factory reject meter. It cost me £1. It was one in a huge box of identical meters at an electronics trade fair many years ago. They had all failed QA and someone must have got hold of them (made in Korea?) and put them up for sale.This one had a dicky display and I took it apart and cleaned it and it's worked ever since... Because it was a 'QA reject' and is also a cheapo brand I only use it on low voltage stuff and it's actually quite nice to use.

author: Stonent
author_rank: Super Contributor
timestamp: April 20, 2014, 01:30:42 am
content: Quote from: Refrigerator on April 09, 2014, 05:51:21 pm

author: Siehbi
author_rank: Contributor
timestamp: April 20, 2014, 06:02:20 pm
content: I have one of these cheapy multimeter... the wires going to the leads detached themselves internally from the probes.Had to electrical tape the wire back to the probe. Mine is the DT830B, No CE marking no CAT rating nothing.Screen has detached slightly from the PCB which has left me with 1 and a half digits..Would not trust these cheap DMM's. Getting an extech ex430 now.Nicholas

author: 128er
author_rank: Regular Contributor
timestamp: April 20, 2014, 06:44:06 pm
content: Quote from: Siehbi on April 20, 2014, 06:02:20 pmThe same happened to my probes. Cheap crap . . .

author: Stonent
author_rank: Super Contributor
timestamp: April 20, 2014, 08:21:53 pm
content: Just worth mentioning, the ones that Harbor Freight sell (the Centech brand) have a battery tester position, so I think they drop one of the higher voltage ranges to make room.

author: dannyf
author_rank: Super Contributor
timestamp: April 20, 2014, 08:37:07 pm
content: I have used those meters since the 1980s (DT830). They rock in terms of accuracy, as well as value. I still have one with me, with a half detached back cover. This thing gives me no excuse to throw it away.

author: Stonent
author_rank: Super Contributor
timestamp: April 20, 2014, 08:44:05 pm
content: Quote from: dannyf on April 20, 2014, 08:37:07 pmI've had a couple that just seem to wander aimlessly on the ohms range.

author: MatCat
author_rank: Frequent Contributor
timestamp: April 20, 2014, 08:59:20 pm
content: I have a handful of the harbor freight freebies, they do actually work well for basic spot checking voltages and such, never tried measuring 10A through it, I think that would be a bit pushing it, but for a second / third / fourth meter just checking logic voltages, it works just fine.

author: dannyf
author_rank: Super Contributor
timestamp: April 20, 2014, 09:22:06 pm
content: I just checked my tool box and I got actually two of them, one DT830B and DM301 (Made in Korea). On a few 2.5v Vref I have (REF3325, LM4040, and two others), the DT830B reads 2.50v spot on, and the DM301 2.48v.Pretty respective for a meter from the 1980s.QuoteThe leads on my DM301 have a resistance of over 1ohm, and super-flexible,. The DT830B leads on the other hand are well made.

author: dannyf
author_rank: Super Contributor
timestamp: April 20, 2014, 09:26:39 pm
content: 7106 (and 7107) are those chips that totally revolutionized an industry and left in its wake lots of dead analog meters.Think about what those $5 meters could do, vs. analog meters 10x or 100x of their prices. Not to mention the consistency of those $5 meters: it is tough to mess them up,

author: dannyf
author_rank: Super Contributor
timestamp: April 20, 2014, 09:59:09 pm
content: Here is one example of alternative uses of those $5 meters: a digital milliohm meter.7106 works by converting input voltage to 1000 count proportional to its Vref (100mv). So if you use a reference resistor in serial with your DUT and the Vref is tied to the voltage drop off the reference resistor, you have gotten yourself a resistance meter. If the reference resistor is a precision 1ohm resistor -> a cheap and accurate milliohm meter is yours, for $5 + some soldering.

author: facumedica
author_rank: Contributor
timestamp: April 23, 2014, 01:04:28 am
content: That multimeter was my first one! It was rebranded and costed me about $30 (argentinean pesos) like 3 or 4 years ago.I changed it for a ExTech Ex-330

author: AlphZeta
author_rank: Regular Contributor
timestamp: April 27, 2014, 11:27:07 pm
content: Well, I have two of those. One was bought 15 years ago while I was in China, the other one I got from Harbor Freight a couple of years ago. While PCB design changed quite a bit, they are both variant of the good old DT-830 (Mastech/Centech etc). The accuracy of these meters are pretty awful right out-of-box, but can be adjusted (via a trimpot) to be reasonably decent.For less than $5, they are actually surprisingly forgiving. I think I mentioned it in a thread somewhere on this forum (a while back) that once I was trying to measure mains voltage but forgot that I had left the lead in 10A.... there was a huge spark and a loud bang.... but when everything was said and done, the only thing that went was the fuse, the meter survived and everything is functional till this day. Because it's cheap, I tend to be quite rough with it... And after 15 years, it's still working!

author: dannyf
author_rank: Super Contributor
timestamp: April 27, 2014, 11:56:10 pm
content: QuoteBecause those meters usually have a 1Mohm serial resistor on the input.QuoteThey are the best value out there, bar none.Most of the issues come from crappy Vref generator - sometimes they are simply a pot to the battery. A LM385 or even a TL431 would fix that.

author: Rick Law
author_rank: Super Contributor
timestamp: April 30, 2014, 04:21:35 am
content: There was another post about the DT830 not so long along when another forum member was talking about decoding the LCD to log the data.Did anyone try that yet?I am itching to try, I would mind hearing from someone who tried before.

author: dannyf
author_rank: Super Contributor
timestamp: April 30, 2014, 03:32:24 pm
content: It is doable to decode multi-com lcds but that not easy;Two simpler alternatives:1) use a display adc with pwm output;2) use a display adc with bcd output - 7135 for example is fairly easy to decode with a mcu. The mcu can then transmitt the data out via a uart. You then have a 20,000 count data logger!

author: mariush
author_rank: Super Contributor
timestamp: April 30, 2014, 04:04:20 pm
content: The multiplexing of the lcd segments plus the various levels of voltage would make it hard to actually process and record the segments active on screen.The oldICL7106is cheap in quantity (<2$ in 100+) and has seven segment display driver, so it would make it much easier to tap into it and get the value. But then again, there are others that have built in i2c/spi output for about the same price so why bother (other than a fun spare time project)

author: Rick Law
author_rank: Super Contributor
timestamp: May 04, 2014, 04:19:55 am
content: It is more so for fun. I have enough 1-2% accuracy logger to use for now. If the DT830 is 0.1% accuracy, that would be a different story.I plan to start with a dead calculator. See how that LCD works and see if I can adapt it to some use. (It would likely be cheaper to get a 1602 LCD from eBay than revive an 8 digit calculator LCD, but that wouldn't be much fun)

author: KC0PPH
author_rank: Unknown
timestamp: May 04, 2014, 06:44:00 am
content: My father bought 10 of them from Harbor Flake for around $2 a piece...He was able to adjust them all and they are decent little (low precision) meters. IMO the hobbyist should have a few of them for when you need a) a cheap meter, b) something to keep in the car, c) using 500 meters while building/testing/fixing things. I just would not be measuring mains or anything with them... As i recall the transistor testers worked alright as well... Just make sure you keep other quality meters around...

author: dannyf
author_rank: Super Contributor
timestamp: May 04, 2014, 11:05:18 am
content: QuoteThe 7107 datasheet suggests that it is a static lcd (single com / backplane). So it is fairly simple: on the polarity change of that com, read all the pins and you should be OK. The lcd shouldn't run very fast so it should work - just lots of pins to connect.QuoteYou can start with a new calculator: most of those tool shops or large box retailers sell 8/10 digit calculators for a dollar or so - they have been my preferred source of lcd panels,

author: Rick Law
author_rank: Super Contributor
timestamp: May 04, 2014, 04:11:20 pm
content: Quote from: dannyf on May 04, 2014, 11:05:18 amGreat mind think alike! I just came back from Walmart and got their $1 calculator, and I then saw your note.I thought that was worth a try - at least I can decode what is on the display with the display ON on rather dead....then, after I make that one work (or not), with a bit of experience under my belt, I can try the "red-melon" calculator. (Yeah, is a kid's toy, looks like a red slides of some melon. Coming from kid/baby toy store, it probably costed more than a 20x4 LCDs. Kid/baby store is awful place to find good deals..)

author: Rick Law
author_rank: Super Contributor
timestamp: May 04, 2014, 04:22:09 pm
content: Quote from: KC0PPH on May 04, 2014, 06:44:00 amI have two of them, normally attached to my power supply - one for Voltage and one on a .1ohm shunt for current. They run off individual isolated power brick and a 7809. The AC power adds some inaccuracy, good enough (+- 2 digits max comparing my UT61E running on battery - I am very surprise at how good they are.)

author: dannyf
author_rank: Super Contributor
timestamp: May 05, 2014, 10:24:20 am
content: QuoteAmazing feat of technology,

author: morpheus
author_rank: Newbie
timestamp: May 06, 2014, 05:42:56 am
content: Yah, that's the one i have to use.