Uni-T UT181A - Board revisions, ESD robustness? - Page 1
Forum section: electronics / testgear

author: lodkolven
author_rank: Contributor
timestamp: November 15, 2019, 08:10:26 am
content: HiUni-T UT181AI've been following Joe Smiths review of the ut181a, just to sadly see him ESD-kill it with the grillstarter.Found out that the meter he is testing is using PCB board revision -5 and that there are at least one newer board revision out in the wild.The second video below shows a review of the ut181a with a newer board revision, -6 this time and there are some significant changes made, mainly some slotting near the smaller fuse and some routing changes as well near the terminals and the fuse.This makes me wonder if the new design might be ready for Joe's magic abuse equipments???Uni-T have tried and failed many times before, maybe they made it this time...Joe what do you think about the borard changes made, do they in any way correlate to the changes you did to your meter?See details in these videos:12:08 into this video (Joe Smith 2016)Compared to19:51 into this video (Darren Walker 2019)

author: joeqsmith
author_rank: Super Contributor
timestamp: November 15, 2019, 01:07:44 pm
content: Quote from: lodkolven on November 15, 2019, 08:10:26 amSorry, but I can't sit through his videos. I tried once and the lack of substance wasn't enough to offset the childish sound effects.I am not sure why you would feel that any changes around the fuse area would have any effect on the meter's ability to survive that do nothing grill starter.I suggest you ask the person posting the video to test it. Theymay need to sort through a few starters to find one similar to mine, but they are cheap. Worst that will happen is they will be clueless. This seemed to be the case when they were going to debunk my life cycle test where I had cracked all four prongs on a Keysight meter. The video was them going on and on about how reliable they thought the meter was.As for the slot, I assume that the open fuse test got them. Someone was telling my how UNI-T had the meter certified. If that cert was legit, there is no way they wouldn't have red flagged this early on.

author: lodkolven
author_rank: Contributor
timestamp: November 17, 2019, 07:29:24 pm
content: Regarding the mods you made to your ut181a, what was the main problem that caused it to fail the grillstarter test?Was it mainly a PCB layout problem or did you have to alter the input circuit in any way to make it survive?Perhaps a video on the mods upcoming?I really like the concept on the ut181a, many things are done right just so sad to see it fail on the ESD testing.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 17, 2019, 08:54:01 pm
content: Quote from: lodkolven on November 17, 2019, 07:29:24 pmHard to say really, not working for them. I would say lack of experienced designers, lack of testing, lack of funds, rush to market... If you want to understand more about solving problems like this, I suggest you watch the couple of videos I made for the UT61E.Quote from: lodkolven on November 17, 2019, 07:29:24 pmIf you work with RF at all and watched the videos, the transient that the meter was exposed to have a sub ns rise time. At these frequencies, the PCB layout IS part of the circuit! Changing the circuit board can have a dramatic effect as was demonstrated.The DMM is a safety device and making any modifications to one is just being stupid. I have no intention of trying to give a play be play for beginners to follow. If you need a robust meter, buy one.The meters I modify for these videos get marked and will eventually be destroyed. These are modified purely for education.Quote from: lodkolven on November 17, 2019, 07:29:24 pmIf you really feel this way, I am not sure why you would be asking me about how to modify it. I've been pretty clear from the start that those wanting to see it improved should be writing letters to UNI-T requesting what you would like to see. This is how you get something changed. Not be being stupid and cutting up a safety device.

author: lodkolven
author_rank: Contributor
timestamp: November 18, 2019, 11:46:08 am
content: Quote from: joeqsmith on November 17, 2019, 08:54:01 pmOk, i've been watching your videos on the UT61E, very interesting indeed, your knowledge and passion for this is quite unique and the fact that you decided to share it with us is just fantastic!It would be hard to find a person with more experience and knowledge in this area than you. Finding one that also is willing to share it's knowledge like you is next to impossible i would say.Quote from: joeqsmith on November 17, 2019, 08:54:01 pmYes i understand, it's a mix of groundloop problems, EM-radiation, energy ending up in the wrong places etc.My thinking was that since it was a 3.3v supply IC that was damaged and not the input circuit on the ADC or other components in the signal path from the terminal to ADC, the main problem might have been caused by either arching between traces/components or being EM/inductively transferred over to the power circuitry and then somehow ended up hurting the 3.3v supply IC. So based on that i was curios how you solved it, from a learning perspective on my part.Quote from: joeqsmith on November 17, 2019, 08:54:01 pmI'll try to reach out to UNI-T and we'll see if we have a fixed UT181B ready for Xmas... :-)I agree with you regarding the safety for sure, in my use case (lab with no HV) i'm also quite pragmatic and see a possible solution here where i could buy the current UT181A doing some mods making it survive it's lab bench life in a sometimes quite dry and ESD unfriendly environment. I think that if i use the modded meter as if it was just rated up to 100V after the mods, but with improved ESD handling capabilities, and use it as such it's OK.It won't be the multimeter that kills me, the real hazard is outside the meter in the DUT itself, you don't need a multimeter to hurt you when the circuit could do it all by it self... :-)

author: joeqsmith
author_rank: Super Contributor
timestamp: November 18, 2019, 12:57:56 pm
content: Quote from: lodkolven on November 18, 2019, 11:46:08 amIf someone asked to borrow your meter after you had made modifications to it and they are injured as a result of your negligence, you may find the cost of a good meter was actually cheap. I mark the meters I have modified not for my own safety but in case they end up in someone else's hands. Seeing the grim reaper or a skull and cross bones, along with a note that states not to use may prevent an injury.Looking forward to seeing that B model.

author: Fungus
author_rank: Super Contributor
timestamp: November 18, 2019, 01:07:01 pm
content: Quote from: lodkolven on November 18, 2019, 11:46:08 amYouhaveseen the meters jumping around inside joe's little box, right? That's with a fairly small amount of energy, nowhere near what AC mains can provide.

author: lodkolven
author_rank: Contributor
timestamp: November 18, 2019, 01:59:57 pm
content: I've been building projects that are AC mains attached for 30+ years, with your reasoning that would totally be out of the question then, or what?I have a strong feeling that the majority of the forum members has built similar projects as well, otherwise they wouldn't be here...I'll for sure continue with my projects, and won't hesitate making them AC mains attached...Maybe i should ditch the UT181 and get a Brymen 869 instead, or hm... maybe get me self a HV-probe and dig out some ignition coils and do my own research... we'll see..Below you can see my latest project, doing some final isolation tests... ;-)

author: Fungus
author_rank: Super Contributor
timestamp: November 18, 2019, 02:33:29 pm
content: Quote from: lodkolven on November 18, 2019, 01:59:57 pmThat why we're suggesting something not made by Uni-T. Uni-T don't make safe meters.Quote from: lodkolven on November 18, 2019, 01:59:57 pmThat's more like it.Does the Uni-T have a compelling feature that you need?

author: totalnoob
author_rank: Regular Contributor
timestamp: November 18, 2019, 03:22:59 pm
content: Quote from: lodkolven on November 18, 2019, 01:59:57 pmI agree with you. however, one problem is that you are putting people in the untenable place of arguingagainsttaking as many safety precautions as you can. I agree that, at least US household voltage, likely will not pose a problem to the majority of these cheap Chinese meters that are out there (otherwise I am sure most of them would be off the market, there'd be lots of class action lawsuits, etc.) especially since I am sure most of those are sold are to "Harry the homeowner" who doesn't know better. I have had a class on NFPA 70E since I work in a commercial facilities environment and the gist of the class was that at about 240V and below (although the class was discussing commercial/industrial 3 phase systems, this is the same voltage that household power comes in at), the biggest danger is electrocution and not arc flash. That's not to say that arc flash cannot happen in the lower voltage systems (i.e. 240V and below) but that it is less likely to be lethal than an electric shock. Therefore, you may get injured if there's an arc flash in your meter, at household voltage, but it should be a survivable event (of course each case is different and I am sure that people have died from arc flash at 240V and below, but the NFPA found that vast majority of people exposed to this voltage and below survive).So, I do agree with you that there is a bit of an overreaction of what is likely to happen with these cheap meters. However, I don't blame anyone for pushing to be more safe and only recommend those meters that actually meet their CAT ratings for household voltages and even I would not use anything but a meter that meets its CAT rating (and is appropriately CAT rated) for industrial/commercial work where voltages can go up to the high end of NFPA's "low voltage" spectrum (i.e. 600V).

author: chickenHeadKnob
author_rank: Super Contributor
timestamp: November 19, 2019, 01:58:26 am
content: Quote from: lodkolven on November 18, 2019, 11:46:08 amIt seems to me that you have fallen in love with UT 181B and are looking for rationalizations to justify a purchase. I checked prices on Amazon, its not particularly cheap given its specifications. $400 is into the range of a good used bench meter. I personally prefer a bench meter for in lab prototype development and use a Brymen 869 as a second companion.

author: joeqsmith
author_rank: Super Contributor
timestamp: November 19, 2019, 02:53:34 am
content: Quote from: lodkolven on November 18, 2019, 01:59:57 pmYour home will normally be CAT II which would normally have much lower fault currents than CAT III. Who knows where the meter will be used. I know I don't.I am guessing that your comment about the ignition coil is in regards to trying to simulate an ESD event. If you watched that second part of the 181A, I think I show the waveform from that little grill starter compared with the 61326 standard. I used to get a lot of UNI-T fanboys whining about how harsh my tests are and them not being realistic. I call it a do nothing test because its so low in comparison with the standard.I am not sure if you could get anything close with an ignition coil. When I designed my ESD gun, I spent a fair bit of time trying to sort out the trigger and waveshape network. Somewhere on this site there's a thread about it. No ignition coil was used.Just on this site, I've seen some pretty poor workmanship. The was someone who had bought a UT181A, cut the back battery cover open and cobbled in some batteries. I think they were taking on to some sort of job sites. It was some of the worse workmanship I've seen. Imagine that exposed battery pack getting wet while your working on a 440, even 220 line and holding that thing. No thanks.Peoples skill and education are all over the map. There is no way I would attempt to put some sort of instructions together for the general public to try and follow.Yea, I know, your skilled and been doing .... for x years. I hear it all the time. My view on it then is you should know better than to attempt to modify any safety device. If you do, you have the skills/equipment needed to design and test your changes. Just the fact that you would ask tells me you are not at that level.Of course, people come up with the idea it's my responsibility to teach them. It's not. This is what college is for. I don't mind explaining the basics like I did with that UT61E series but I had people suggesting I should make a kit for the kids to mod their meters! That's not ever going to happen.

author: lodkolven
author_rank: Contributor
timestamp: November 19, 2019, 07:55:07 am
content: Ok Joe, i promise to never ever modify my multimeters, at least not for other than educational reasons.But i can also promise that i will never ever stop searching for knowledge in areas i'm lacking, doing so i'll for sure try to do it by learning from the most effective source of knowledge. In the area of ESD/safety protection of multimeters you Joe are my current top of the line source of knowledge, i'm utterly humble to your passion and experience in the field and wish nothing else than that you find the joy/pleasure in sharing and will keep doing so at the same or higher level in the future.And no it's not your responsibility to teach us, not at all, but having a discussion about a problem and sharing doing so often crafts new knowledge among the participants, even you i believe.I'm in no way the almighty EE, i have areas of expertise and many black holes in my knowledge map that needs to be filled, the aim is to be doing so by trying to share my knowledge with other along the way, that's the spirit i believe in...Everyones driving force is different, my strongest is collecting new knowledge, yours i don't know but something strong is driving you as well otherwise we shouldn't have met here.Since i live in Sweden i'm happily not exposed to the suing madness practice you've been growing for quite some time in the US, i understand that one needs to be ever more cautious in the US than Sweden/Europe.

author: lodkolven
author_rank: Contributor
timestamp: November 19, 2019, 09:08:10 am
content: Quote from: chickenHeadKnob on November 19, 2019, 01:58:26 amI've been looking at the Fluke 289 but dropped it, mostly due it's diet of batteries and slow/outdated cpu and screen.The UT181 is in some way a modern 289 with specs(safety/robustness NOT included here) on par or above the 289 at half the cost, too bad it's a UNI-T product and not a Brymen one...Your approach with a proper bench meter and a Brymen 869 as complement is a good combo i believe...

author: lodkolven
author_rank: Contributor
timestamp: November 19, 2019, 09:20:25 am
content: Quote from: joeqsmith on November 19, 2019, 02:53:34 amCoils makes for easy HV generation and triggering is easy as well, but controlling the pulse-shape is another challenge, if possible at all.You could create a pulse-shape that introduces some energy into the DUT and to some extent it would be possible to do some meaningful testing, you wouldn't be 61326 compliant but anyway.Charging a CAP is the way to go i believe, triggering and pulse-shaping is a bit of challenge but doable.Quote from: joeqsmith on November 19, 2019, 02:53:34 amThat one looks like it's been done blindfolded with an anglegrinder, not the ptrettiest by far.

author: evava
author_rank: Regular Contributor
timestamp: November 19, 2019, 11:22:14 am
content: Quote from: lodkolven on November 19, 2019, 09:08:10 amIMHO, I advise you not to long for/not to buy UT181a.I have been owning both meters (F289 and UT181a) for the few years and now I always (between the two) grab F289 (despite that bad display contrast).Display is the only thing which UNI-T excels in, nothing else!Today I regret the purchase of this expensive UNI-T, but then I was like you.Batteries are no problem at F289 (Panasonic Eneloop), only problem is bad contrast.With F289 you have the meter you can rely on, while ut181a is just very expensive UNI-T !Half the cost, no trust - you do not want that!

author: joeqsmith
author_rank: Super Contributor
timestamp: November 19, 2019, 03:04:28 pm
content: The 181 certainly boots faster, can plot data MUCH faster, some improvements in the menus from what I remember.Failed the do nothing grill starter start.Uses non-standard battery.Can not use meter while battery is charging. Just an FYI, I just recharged the battery on mine which required over 24 hours this time to reach 100%.No AC line adapters included with the charger.Lens is easily scratched.Accuracy, temperature drift, speed, all really good.One of the reasons I bought the Brymen BM869s was the two TC inputs. The 181A also has this feature and it works great.One of the best bar graphs I have seen.3dB point is one of the highest.They used some decent components in this meter.They offer a BLE adapter and people have documented the interface for it. You can see it in operation here:https://youtu.be/e_YzwO62feQ?t=1207And of course, there is that display.Personally, I think it was a big step up for UNI-T. The meter just needs a few things addressed and it could be a great meter. Cost wise, I just paid the same amount for the 121GW. If you want to talk about trust, the UNI-T will show HV in the presence of HV. I can't say that about the 121GW in its current state.If give UNI-T a pat on the back for their effort and really hope they produce an improved version of this meter.The only other UNI-T product I like is that UT210E current clamp but we have now had our second switch start to fail. I would gladly pay UNI-T more for a higher quality version of this meter.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 19, 2019, 06:22:26 pm
content: I hope they have taken a good path with their newest looks in the bench meters, UT-8000 series like the 20,000, the 60,000 counts and the 6 1/2 digit tooneed some teardown loll

author: lodkolven
author_rank: Contributor
timestamp: November 25, 2019, 07:06:37 pm
content: Since i know there are quite a few UT181A owners on this forum, I think it would be interesting to see how the internal PCB has evolved through the different revisions.I've seen on the net that there are at least 3 different revisions out there, -3, -5 and -6, most likely higher revisions exist since the -6 dates back a few years at least.If you have a UT181A i think many of us would be interested in seeing images of the PCB, especially if it's a -7 or higher revision.Feel free to post some pictures...

author: Fungus
author_rank: Super Contributor
timestamp: November 25, 2019, 09:00:21 pm
content: Quote from: lodkolven on November 25, 2019, 07:06:37 pmMost likely it'sdevolved - to make it cheaper to produce.

author: lodkolven
author_rank: Contributor
timestamp: November 26, 2019, 11:47:13 am
content: I think you're wrong this time, going from rev -5 to -6 they added a few isolation slots in the pcb and made some extra HV-clearance by moving some traces further away from HV-areas, maybe even more changes hard to tell from just looking at Youtube videos.

author: DarrenWalker
author_rank: Newbie
timestamp: December 17, 2019, 01:22:52 am
content: I don't play with Grill starters unless I'm cooking up T-Bones in the summer.UNI-T has made vast improvements to their multimeter lineup and continue to impress.They are by no means perfect but are perfectly priced and usually (though not always) offer a-lot of value.The UT181A is no exception, it has proven to be a very reliable dmm. My biggest gripe is the BT which can be finicky, especially when you need it most!You can watch some folks use and abuse these things until the cows come home but in the real world they usually perform quite admirably and for the average CAT II homeowner/Electronics Hobbyist requirements they are more than adequate.Of course they are constantly improving their PCB's and new revisions are per the norm. Anyone telling you otherwise is completely out to lunch.

author: Fungus
author_rank: Super Contributor
timestamp: December 17, 2019, 08:29:54 am
content: Quote from: DarrenWalker on December 17, 2019, 01:22:52 amOk.Quote from: DarrenWalker on December 17, 2019, 01:22:52 amSo.... it'snotreliable.

author: joeqsmith
author_rank: Super Contributor
timestamp: December 17, 2019, 11:34:30 am
content: It's our buddy who made debunk video where he blabbed on for a half hour about how reliable the Keysight meter was after I showed how all four tangs on the glass filled detent spring broke after a couple thousand cycles. Never even pulled the meter apart to show the detent spring. It did have some sound effects that any two year old child would enjoy. It was the first and last video I have watched of theirs.I can fully understand that a non technical person would see that grill starter as a grill starter, even though I took the time to characterize it and show how lame it is compared with what the IEC standards call for. This is some pretty basic stuff but then again, I though the detent spring was pretty basic too.Yes, that grill starter has damaged several UNI-T products. Recently it took out some older revision of Dave's EEVBLOG 121GW. I'm always amazed when it damages a meter.Welcome to the EEVBLOG site.

author: Fungus
author_rank: Super Contributor
timestamp: December 17, 2019, 01:26:38 pm
content: Quote from: joeqsmith on December 17, 2019, 11:34:30 amI remember it well, I just didn't remember the name.

author: DarrenWalker
author_rank: Newbie
timestamp: December 17, 2019, 10:57:17 pm
content: Unfortunately BT is NOT reliable on the UNI-T UT181AIt's too bad really as it's a huge part of the appeal on this meter.

author: DarrenWalker
author_rank: Newbie
timestamp: December 17, 2019, 11:13:24 pm
content: Joe,My crew have used those same meters for over 5 years and we haven't had one issue.Why keep trying to blow smoke when there's isn't any?Hmmm, I can think of another use for that grill starter.

author: DarrenWalker
author_rank: Newbie
timestamp: December 17, 2019, 11:19:27 pm
content: >>>Welcome to the EEVBLOG siteThankyou, Dave is a trooper. 100% respect to him and this great EEVBLOG Forum.

author: DarrenWalker
author_rank: Newbie
timestamp: December 18, 2019, 05:55:06 pm
content: I spoke with a UNI-T engineer last year, they don't have any plans on making the Firmware user upgradeable (at least in the short term), which is really too bad. That could have easily resolved a-lot of the dmm's snafus.Darren

author: mcinque
author_rank: Unknown
timestamp: December 19, 2019, 09:41:53 pm
content: There is a huge difference in components when you purchase any UNI-T from eBay or from a "known" name like Farnell or Distrelec.It seems UNI-T have different markets and only purchasing from reliable distributors you can get the "certified" version (CE in my case).My UT61s from Distrelec have decent input protection with much more MOVs in respect to the ones I saw on YouTube reviews or in teardown images on the web.I'm not saying that UNI-T can challenge Fluke, but those tests aren't decisive; the DUT may come from a chinese eBay reseller in the "cheaper version" with almost no input protection.

author: DarrenWalker
author_rank: Newbie
timestamp: December 20, 2019, 01:20:26 am
content: That's a good point. I realise European standards are usually enforced allowing for a better overall product. However, in all of my reviews the UNI-T multimeters are sourced from regular Ebay/Ali * vendors including the UT181A which was surprisingly well put together. It's very easy to cherry pick a multimeter for a review but its alot more useful to the public in general if the meter is sourced from a regular vendor to gauge the Q/A correctly.

author: spiff72
author_rank: Regular Contributor
timestamp: June 18, 2020, 01:26:35 pm
content: If you have a direct line to an engineer at UNI-T, why wouldn't you inquire about possible board revisions to this to address the ESD concerns about it? Send them a link to Joe's video perhaps?

author: spiff72
author_rank: Regular Contributor
timestamp: June 24, 2020, 11:12:47 pm
content: I know this is an older thread, but I just wanted to chime in and say that I just ordered and received a Triplett 9065, which appears to be exactly the same as this Uni-T UT181A. Just for grins I opened up the back to see the PCB, and it is marked as 20130530-6 UT181A-MAIN on the top of the board. In comparing to the video from joeqsmith, there appears to be a few changes in the lower right (when viewing the back of the board (battery connector side). I see a line of three small vias that were reoriented to be vertical instead of horizontal, and there may be a half-round clearance added around these on the ground plane. I also see the L-slot that was added at the bottom of the smaller fuse, and one thing that I am not sure is a trick of the camera, but there is a trace from the small SMT cap (C112) to the right of the larger fuse that is visible in Joe's video, but is not visible on my board. It may be on the other side of the board, but it is MUCH more visible in Joe's video, so I wonder if that trace was shifted to the other side of the PCB??Anyway, do any of these changes appear to reflect possible changes to resolve the ESD issues that Joe fixed in his meter? Just curious... Photos of my board are attached.If anyone wonders, I ordered this meter from Amazon ($250) but it is also available from TEquipment.net as well. It is a bit cheaper at TEquipment ($223), but I opted for the Amazon purchase for easier returns if it turned out to be different that the Uni-T model (and it was still in transit to TE when I chatted with them prior to ordering).

author: spiff72
author_rank: Regular Contributor
timestamp: June 24, 2020, 11:13:50 pm
content: One more image of my board, and a screen grab from joe's video:

author: oktay50000
author_rank: Newbie
timestamp: July 23, 2020, 07:54:57 am
content: Triplett 9065Is it exactly the same model as 181a or it has better isolation,or any changes inside?Or just a branding game

author: JACKENPACKEN
author_rank: Newbie
timestamp: November 07, 2020, 07:10:48 pm
content: I see the difference. i ques the picture below is your triplett. seems there is cap under the top fuse and metallic cap divider. would love to see joes comparison between these two DMM's

author: djidji
author_rank: Newbie
timestamp: March 19, 2021, 08:40:07 pm
content: just bought it and I'm much more happy with it then with my U1282A.

author: janiorib
author_rank: Newbie
timestamp: May 30, 2021, 01:26:04 am
content: There was a minor revision in the PCB since the sr test. joeqsmith, these changes i think are still not enough for a new test