BM869S not reading correct voltage - Page 1
Forum section: electronics / testgear

author: LDDM
author_rank: Contributor
timestamp: July 11, 2024, 12:50:53 pm
content: Hi Everyone,First post here. Some time ago, I bought a BM869s after watching some videos of EEVblog on YouTube. The first one I received had a leaking battery, so I was sent a second one and was never given a return label for the first one.Long story short, I repaired the first one and had 2 brand new BM869s. Both of them were working perfectly for 1.5 years of really light use (for hobby project). However, the last time I used them, for some reason, both gave me incorrect voltages AC and DC.At first, it was with AC voltages from mains power (230V). I measured between Live and Neutral and only got around 156V (now it is 0V). I did the same with another multimeter (Major Tech brand) and I had the expected voltage (230V to 240V). Then, I tested with my power supply (RD6006P) a DC voltage and had the same issue: I got lower voltage than expected (please see pictures below).Has anyone had this issue? Can it be resolved, or is the multimeter fried (both have a similar issue)?Please also see video here:https://youtube.com/shorts/29_wXrWJ6-4?feature=share

author: Fungus
author_rank: Super Contributor
timestamp: July 11, 2024, 01:49:55 pm
content: It seems impossible that both would fail simultaneously. These areveryrobust meters.There must be some information missing.

author: LDDM
author_rank: Contributor
timestamp: July 11, 2024, 04:27:47 pm
content: Maybe I did something wrong by accident, but these are not the first meters I've used, and I've never managed to break a meter before. Additionally, I did not do anything unusual with them, only measured battery voltages, voltage in small circuits (ESP32, Arduino, and similar), and very few times mains voltage.What could cause this sort of issue?(Note: The first meter with a leaky battery also had an issue with the amp jack sensor, which I fixed.)

author: LDDM
author_rank: Contributor
timestamp: July 11, 2024, 04:35:12 pm
content: I just found someone with a similar issue, it seems:https://www.eevblog.com/forum/testgear/brymen-bm869s-no-longer-reading-ac-voltage/msg5529979/#msg5529979Update: Also find this (I'm having this issue as well)

author: joeqsmith
author_rank: Super Contributor
timestamp: July 11, 2024, 10:43:20 pm
content: I bought my first one in 2016. Even after all of my abuse, both meters continue to work fine. For two to fail, there's more to the story.Switch point hunting is a common problem. Agree, it should never happen but it's not something that has ever caused me a problem outside of the reviews. The BM789 should be solid in this regard.

author: Martin72
author_rank: Super Contributor
timestamp: July 11, 2024, 11:26:01 pm
content: A few questions for the OP:-Batteries in the devices are OK ?-Test leads OK?-Have you tried a different voltage source, e.g. a battery?-Tested other measuring ranges, current, resistance, capacitance, frequency?-What are the environmental conditions where the meters are usually located, i.e. average temperature and especially humidity?It is very unlikely that both have broken, unless both have suffered the same fate.

author: TheDefpom
author_rank: Frequent Contributor
timestamp: July 11, 2024, 11:26:58 pm
content: Maybe try a different set of test leads, if you are using the same pair of leads that could be the problem instead.

author: radiolistener
author_rank: Super Contributor
timestamp: July 12, 2024, 04:42:22 am
content: Quote from: LDDM on July 11, 2024, 04:35:12 pmI know Brymen brand by their faulty gold-plated probes.The one pair that I got with my new Brymen BM867S is going to 5-10 Ω resistance just after 2-4 years of very rare and light usage (just as a home dmm for diy projects). I contacted with Brymen about it and they said the following:QuoteIn reality there is some issue with contacts inside probes banana plugs, if you push and pull the wire back and forth it can solve issue for some time, but it again going worse and worse with time. So there is no way to fix it with no probe disassemble. And if you disassemble it you can just put it into garbage bin because it has not repairable design.So, first try to replace original Brymen gold-plated probes with some new one from another brand, even cheap Chinese 2 USD probes should work better.

author: Antonio90
author_rank: Frequent Contributor
timestamp: July 12, 2024, 06:04:58 am
content: As@radiolistenersaid, try different probes or a cable with banana plugs. I have a set of brymen leads with intermittent connection problems. Drove me crazy for a while too.

author: LDDM
author_rank: Contributor
timestamp: July 12, 2024, 07:16:11 am
content: Thank you for your replies. If I did something wrong, I genuinely do not know what, but I would happily take the "blame" and learn from it!How can something like this happen? What would it take to break a meter like this?(Note: No blown fuses, no burned components in the meter.)Moreover, I replaced both 9V batteries this morning and tested the test leads / used banana test leads from my PSU with no luck.So I did a few tests to see, please see the table below:

author: J-R
author_rank: Super Contributor
timestamp: July 12, 2024, 09:27:38 am
content: The selector switch on the BM869s has multiple pieces with wipers in specific locations. Any chance you disassembled that and didn't reassemble it 100% correctly?

author: Fungus
author_rank: Super Contributor
timestamp: July 12, 2024, 10:32:35 am
content: Quote from: LDDM on July 12, 2024, 07:16:11 amWithout disassembling it? Alot.Two of them breaking simultaneously is very suspicious.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 12, 2024, 10:56:11 am
content: yep strange issue ... 2 of them ?i would have said high voltages spikes, blown fuses, battery ... the usuals suspects ??if probes are ok not loose ... dismantling associated problems ... sure its hardware related ... movs tvs ... bad dial contacts or broken onesprobing inside them .... ask brymen for a schematic under non disclosure if they would help in some waysyou do need to read the internal dividers in manual mode and keep the same impedance for many ranges ... ?you have many schematics with the meter chipset who could help you follow voltages paths ...

author: Fungus
author_rank: Super Contributor
timestamp: July 12, 2024, 11:22:31 am
content: How were they stored? Could they have been exposed to weird vapors or liquids?Could anybody have "borrowed" them without you knowing?

author: LDDM
author_rank: Contributor
timestamp: July 12, 2024, 11:31:15 am
content: Yes, so I disassembled the first meter to replace the 9V battery connector after the provided battery leaked and seeing the seller did not want to get it back (it was replaced under warranty). Afterwards, the meter turned back on but was stuck with "InErr" (jack beep). I managed to find the issue: the two sides of the amp jack were connected together due to a soldering issue, causing the meter to think the lead was in the amp jack. After that repair, the meter went back in the box, so I never really used it (except one time where I had to measure the temperature in my fridge) so maybe it had other problems that i did not see at the time.Yesterday, I disassembled the rotary switch of this meter for the first time (to check if it could be the cause of my problem). I marked with a Sharpie the position of the switch before taking it apart and took the following pictures (please ignore the position of the lead, was testing the jack beep feature).For the second meter, I never disassembled the switch, i only check if i could have blown a fuse (none were blown).The strange thing is that the last time I used my main meter (the second one) several months ago, it was working normally and has been sitting unused on my desk until now. o my knowledge, no one has used it besides me.I live in a tropical climate with temperatures around 25-35°C and humidity over 80%.I will try to clean the board of the first one with some electronic cleaner and see if it makes any difference.Update: Forgot one picture

author: joeqsmith
author_rank: Super Contributor
timestamp: July 12, 2024, 12:04:06 pm
content: You work on electronics without proper ESD protection?I see three photos of one side of the switch, none of the other.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 12, 2024, 12:14:17 pm
content: ? is the dial has being flipped by mistake or a contact has flown into spaceyou have 3 pairs of pcb traces and i see only 2 contacts = 2 pairsyou seem to miss the one near the center holem or more than 3 since you have some level shifting in the pcb tracessearch for teardown videosthis site has photos who does show 2 contactshttps://lygte-info.dk/review/DMMBrymen%20BM869s%20UK.html

author: Fungus
author_rank: Super Contributor
timestamp: July 12, 2024, 12:19:50 pm
content: You're definitely missing some switch contacts here...(I think there should be four of the gold spring things on the dial)

author: Martin72
author_rank: Super Contributor
timestamp: July 12, 2024, 12:20:33 pm
content: QuotePhew, that's right on the edge.For such regions, we install dedicated "tropicalized" measuring devices in our system, for example.

author: coromonadalix
author_rank: Super Contributor
timestamp: July 12, 2024, 12:23:18 pm
content: yeah but see my link on my post we see only 2 contactshttps://lygte-info.dk/review/DMMBrymen%20BM869s%20UK.htmla simple dial miss-alignment in functions

author: LDDM
author_rank: Contributor
timestamp: July 12, 2024, 12:26:23 pm
content: Sorryi forgot one picture (please see update to my previous post, Meter_16)

author: Fungus
author_rank: Super Contributor
timestamp: July 12, 2024, 12:32:18 pm
content: Quote from: coromonadalix on July 12, 2024, 12:23:18 pmHere, too...https://www.eevblog.com/forum/testgear/brymen-bm-867-teardown-pictures/msg156229/#msg156229But that makes no sense to me.

author: LDDM
author_rank: Contributor
timestamp: July 12, 2024, 01:59:56 pm
content: I just found this post from 2022 of someone having (I think) the same issue.https://www.eevblog.com/forum/testgear/brymen-bm869s-suddenly-weird-behaviour/Similar thing here. It seems to be more common than I thought...https://www.eevblog.com/forum/testgear/brymen-bm869s-stopped-measuring-ac-volts/25/Port from 2018 with similar problems:https://www.eevblog.com/forum/repair/brymen-bm869s-ol-problem-with-ac-measument/msg1918175/#msg1918175

author: joeqsmith
author_rank: Super Contributor
timestamp: July 12, 2024, 05:00:45 pm
content: Sadly as you have seen, seldom people who post about their problems ever provide a conclusion.I live near fresh water and it's not a problem like other parts of the USA. I've never had to consider conformal coating. Do you have to store your electronics in special containers or is not a problem where you live? Is the humidity always high enough that ESD isn't a concern?

author: J-R
author_rank: Super Contributor
timestamp: July 12, 2024, 06:52:25 pm
content: The BM869s is actually pretty well sealed. There are gaskets/o-rings around the battery cover and the banana jacks, even the screw heads. So I don't think humidity would impact it.But you could still fully inspect the PCB under a microscope looking for any solder issues or corrosion, clean selector switch and jack contacts.A side note is that each jack's BeepJack feature does not function if their respective fuse is blown, so double-check those.What 9V batteries are you using?

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 12, 2024, 07:23:17 pm
content: Can you send it to manufacturer for repair at reasonable cost?

author: robert.rozee
author_rank: Frequent Contributor
timestamp: July 13, 2024, 01:51:24 am
content: Quote from: LDDM on July 12, 2024, 07:16:11 amhave you checked the meter leads using a known-good multimeter? this meter may be even the cheapest "dm830" giveaway from harbour freight.from your results i'm rather suspicious that all your leads have been 'stretched'; when a multistranded cable is stretched it is possible foreverystrand to be broken, but each in a different location down the length of the cable. the result is that while the cable may appear to have end-to-end continuity at first, over time as oxidization occurs due to moisture ingress the cable becomes highly unreliable. it could well be that the sheathing Bryman uses happens to be particularly susceptible to moisture ingress in high humidity environments.the risk of stretching cables is why meter leads shouldneverbe wrapped tightly around the instrument, or in any other way subjected to force along their length. good leads are made of multiple very fine strands to provide for flexibility, and those fine strands are more susceptible to breakage than heaver ones.cheers,rob :-)

author: J-R
author_rank: Super Contributor
timestamp: July 13, 2024, 02:36:08 am
content: He did say he tried different leads:https://www.eevblog.com/forum/testgear/bm869s-not-reading-correct-voltage/msg5570587/#msg5570587

author: mqsaharan
author_rank: Regular Contributor
timestamp: July 13, 2024, 05:01:01 am
content: Quote from: LDDM on July 12, 2024, 07:16:11 amIf all else is all right, I mean, if there is no problem with the support circuitry of the processor(s), it could be (analog front end) processor die rot. As Dave once said and I quote "One of the failure modes seem to be related to some sort of processor die rot."https://www.eevblog.com/forum/testgear/brymen-bm789-360289/msg5042728/#msg5042728And in his next message (in the same thread,) he said that Brymen uses well known brand but he cannot disclose because of NDA.I think it is Fortune Semiconductors. For some of their meters, they might be using custom chips but I doubt it will be the case with all their products.I don't own any Brymen meters. I might have tried to trace the circuitry to figure out the chip they are using.

author: LDDM
author_rank: Contributor
timestamp: July 13, 2024, 07:10:27 am
content: Quote from: joeqsmith on July 12, 2024, 05:00:45 pmYes, I also noticed that there is no conclusion, but I found a post on Reddit, and the author responded to my comment. He had the exact same issue I have, so he sent it to Brimen, and they could not figure out the issue. They advised sending it to Taiwan (which was too expensive), so he just bought a Fluke.See his post here:https://www.reddit.com/r/AskElectronics/comments/lcembb/comment/lcu67bw/?context=3If I remember correctly, at the start I also only had issues with AC voltage but did not investigate as I did not have time. But now, as stated, nothing works except continuity and small resistor tests (but I don't know for how long...).Regarding ESD, to be totally honest, I'm relatively new to "advanced electronics" (although I've been tinkering for quite some time now and designing really simple PCBs for hobby projects), and I do not have the right gear. I need to invest in some mats and a static wrist strap, I think.Where I live, the average humidity in winter (dry season) is 80% to 86%, and it regularly reaches 92% during the day.Usually, I do not have issues with electronics. No issues with 3D printer main boards, computer parts, Raspberry Pis (although the Wi-Fi chip metal shield always rusts...), or anything else.

author: LDDM
author_rank: Contributor
timestamp: July 13, 2024, 07:27:16 am
content: Quote from: J-R on July 12, 2024, 06:52:25 pmYes, like you said, it is very well sealed, with o-rings at the jack, battery, and all around the shell as well. I would love to check it with a microscope, but I need to buy one.I will order one and see if I can find something, but by looking at the board closely, I did not notice anything unusual. By the way, any recommendations for a cheap USB or HDMI microscope?Yes, I have checked the fuses on both meters, and they are all okay.I was using a Duracell Plus (6LR61) in the first meter and a Varta (6LP3146, long life Alkaline) in the second meter. Yesterday, I bought a cheap brand (PKCell 6LR61 long life "Ultra" alkaline) to try and see if it makes any difference.Unfortunately, no difference at all.

author: LDDM
author_rank: Contributor
timestamp: July 13, 2024, 07:44:47 am
content: Quote from: BeBuLamar on July 12, 2024, 07:23:17 pmI did not check what it would cost yet, i have to ask local post, DHL and Fedex.Quote from: robert.rozee on July 13, 2024, 01:51:24 amI only tested resistance of the lead with the multimeter itself (which seems good), they were my only multimeters seens i bought them, so i have to buy a new one / borrow to check. However, is tested with my PSU lead witch are good.

author: J-R
author_rank: Super Contributor
timestamp: July 13, 2024, 08:04:20 am
content: For sure an odd situation, still feels like we're missing something...But maybe Brymen got a bad batch of a component. You could e-mail them with the serial numbers and see if they come back with any help.Some other random thoughts:- enter calibration mode and note the display in different switch positions, but don't actually calibrate it (https://www.jackenhack.com/calibrating-brymen-bm-series-multimeter/)(on my BM869s, I get 2.50000 for VFD and VAC, 0.00000 for VDC, 000.000 for mVDC, 250.000 for mVAC, 0000.0C for T1/T2, 000.00 for capacitance, 250.000 for resistance, 50.0000 for A/mA and 500.000 for uA.)- connect maybe around 1VDC to the input and using another DMM, follow that 1V input as far as you can on the PCB to see where it goes- also with the same 1VDC, bypass the obvious parts of the COM & V input protection and see if there is a difference- power the DMM with a DC supply (carefully!!!) and note the power draw, or, are the 9V batteries still full after using them with the DMM for a bit?

author: LDDM
author_rank: Contributor
timestamp: July 13, 2024, 08:07:29 am
content: Quote from: mqsaharan on July 13, 2024, 05:01:01 amSo, if the failure I'm seeing is related to this, there is little to zero chance that it could be fixed, right? Unless I can get a working processor and the matching firmware.I would love to send one of them to Dave if he wants to have a look at it. I even have a family member going to Australia next week, so it would be cheap to get it there.I will investigate and see if I can find the issue, but I have to buy a new meter first!

author: LDDM
author_rank: Contributor
timestamp: July 13, 2024, 08:39:11 am
content: Quote from: J-R on July 13, 2024, 08:04:20 amJust checked the serial numbers, and they could be from the same batch: MFR.#: xxxxxx240 and xxxxxx185 (all "x" are the same).Regarding the values in calibration mode, I also have the same on both meters (VFD: 2.50000, VAC: 2.50000, VDC: 0.00000, mVDC: 000.000, mVAC: 250.000, T1/T2: 000.0C, Diode/Cap: 000.00nF, Resistance: 250.000, A/mA: 50.0000, and uA: 500.000).I powered the meter with my RD6006P at 9.1V, and it drew 0.0038A with a peak at 0.0051A, depending on the mode.For the other tests, I will buy a multimeter locally (might be a Uni-T for now) and revert back.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 13, 2024, 11:09:38 am
content: I don't think it's bad leads. Bad leads generally cause bad reading in resistance but not voltage.

author: Fungus
author_rank: Super Contributor
timestamp: July 13, 2024, 03:06:44 pm
content: I think it's time for Dave to dig out his original Brymens and give them a workout.He's been threatening to do it for ages...

author: Fungus
author_rank: Super Contributor
timestamp: July 13, 2024, 03:07:47 pm
content: Quote from: LDDM on July 11, 2024, 12:50:53 pmHow long ago, exactly?

author: LDDM
author_rank: Contributor
timestamp: July 14, 2024, 07:11:42 am
content: Quote from: Fungus on July 13, 2024, 03:07:47 pmSo I received the first one (with the leaking battery) in the first week of May 2021, and the replacement meter sometime later. I don't really remember if it was in May or two months later, as I was not in the country and received the first one just before leaving.

author: Fungus
author_rank: Super Contributor
timestamp: July 14, 2024, 10:43:45 am
content: Quote from: LDDM on July 14, 2024, 07:11:42 amSo only 3 years old.

author: floobydust
author_rank: Super Contributor
timestamp: July 14, 2024, 08:40:54 pm
content: Does Brymen even issue RMA's for off-warranty goods? I'm not sure they do repairs.OP, the high cost to ship it back to Taiwan, customs paperwork, insurance, your time - just toss these in the garbage and buy something new.With no schematic or IC datasheets, troubleshooting is difficult, and there are known quality issues, as with any product.There is a safety issue with a multimeter that "fails to give an accurate voltage reading, resulting in the operator falsely believing the electrical power is off or low. This poses an electrocution hazard."If this malfunction is due to a Brymen defect then a product recall would be in order and the 61010 certificate would get revoked for the models affected.

author: BeBuLamar
author_rank: Super Contributor
timestamp: July 14, 2024, 09:56:44 pm
content: Quote from: floobydust on July 14, 2024, 08:40:54 pmSo you meant if you live outside of Taiwan which I believe most of us do then after the warranty period there is no service for the Brymen?

author: Fungus
author_rank: Super Contributor
timestamp: July 14, 2024, 10:30:23 pm
content: Quote from: BeBuLamar on July 14, 2024, 09:56:44 pmBrymen works through resellers so it probably depends on where you live.Brymen Europe has a service option listed on their web site but I don't know the pricing for diagnosing/repairing/calibrating a non-working BM869s. It might not be economical, these aren't Fluke price levels or profit margins.

author: floobydust
author_rank: Super Contributor
timestamp: July 14, 2024, 10:51:30 pm
content: Quote from: BeBuLamar on July 14, 2024, 09:56:44 pmNorth America - yes, they are locked out. OP's Mauritius I have no idea.There is no mention on any website of dealers, distributors, repair/cal centers which adds to the mess. As soon as you need to ship it anywhere, major expense.They should be sent to Brymen TW for an autopsy, see if they need to issue a recall.

author: LDDM
author_rank: Contributor
timestamp: July 17, 2024, 04:53:30 am
content: Sent an email to the only email i could find on Brymen.com (info@brymen.com)Check everywhere could not find any support email. If someone know the support email for Brymen Taiwan, would greatly appreciate if you could share it.I will update this post if i get any reply.

author: joeqsmith
author_rank: Super Contributor
timestamp: July 17, 2024, 05:10:53 am
content: That's all I ever used.

author: radiolistener
author_rank: Super Contributor
timestamp: July 17, 2024, 07:11:43 am
content: Quote from: robert.rozee on July 13, 2024, 01:51:24 amIn my case the leads was never stretched and it was stored in ideal home conditions (about 20-25°C and and dry air, no moistures and chemicals in the room), I used them very carefully and wiped the gold needles with cotton wool and 95% ethyl alcohol.But my new golden plated Brymen leads, just out of the box, was about 0.09Ω which is twice worse thanthese Chinese leadswhich is about 0.04Ω. And my Brymen gold plated leads going worse and worse with time despite the rare and careful usage.Now they are lying with no usage in the box, because I use Chinese leads. Periodically, just out of curiosity, I check the Brymen leads and they show a stable high resistance degradation over time. Their current resistance is about 10Ω...I'm almost sure these leads was developed with some hi-technology which allows to get so bad resistance degradation over time, because I never seen such effect on any kind of leads. So, I think they using some kind of nano-technology materials which allows to get so high and quick resistance degradation, probably in order to make leads unusable after 1 year, so the user will go to shop to buy a new replacement... Why I think that they using some kind of hi-tech nano-technology? Just because I can’t even imagine how it’s possible to deliberately make probes with such degradation over time effect...But thanks to Chinese guys, they make cheap leads which has a little worse initial resistance, but their resistance is very stable and don't change over time...Regarding to the Brymen DMM itself, it works. But it has high sensitivity to a static electricity, there was some strange effect when I peel the protection film from the display - when I put my hand near display, it leads to DC voltage spike and LCD segments flashing. This effect was very high when I tried to put a plastic pencil near display. LCD segments was flashing even when DMM was powered off. Probably some issue with shielding and plastic material properties. After years, it still has static electricity effect, but now it is a little bit less visible (maybe because I'm used to it).

author: radiolistener
author_rank: Super Contributor
timestamp: July 17, 2024, 07:27:44 am
content: Quote from: LDDM on July 17, 2024, 04:53:30 amI contacted with Brymen using info@brymen.com, but they can't help with leads issue, they propose to ask help from seller, so if you bought it on internet shop which don't have after sale warranty, then there is no warranty at all...

author: floobydust
author_rank: Super Contributor
timestamp: July 17, 2024, 08:10:18 pm
content: Quote from: radiolistener on July 17, 2024, 07:11:43 amWhat are you talking about, 80% humidity tropical environment has pretty much nothing for ESD. Activating LCD segments with static charge takes a very high level electric field and the multimeter must be connected to something big, not just sitting there by itself.Your bench might have a problem. Laminate flooring is the worst or that composite wood benchtop in the pic.It's normal the DCV jumps around when handling any multimeter. "Segments flashing" I have no idea what that looks like, is that the bar graph? They can only flicker due to being floating i.e. driver IC output is not working, as in the multimeter is powered off or maybe a firmware error does not properly turn off annunciators/segments but that's something that can be tested.High humidity causes oxidation and corrosion, I would suspect the rotary switch or interconnects (headers).I think a question at hand is if Brymen TW offer any support - repair, cal, parts etc. after warranty.

author: radiolistener
author_rank: Super Contributor
timestamp: July 18, 2024, 12:46:42 pm
content: Quote from: floobydust on July 17, 2024, 08:10:18 pmThis is not bench, this is Brymen DMM issue. It very sensitive to static electricity, due to properties of DMM case plastic materials. It works like electric machine, producing static electricity when you touch transparent plastic window over Brymen DMM display... You can touch it with finger, in that case you can even feel static electricity on transparent plastic window surface and its discharge to finger leads to LCD segments flashing. Other equipment don't have such effect, only Brymen DMM. And it has this electrostatic effect in different rooms and different environment conditions. Just touch DMM display and you can see it's DC measurement spikes...I think this issue is present only on BM867 model, because it don't have shielding as BM869

author: radiolistener
author_rank: Super Contributor
timestamp: July 18, 2024, 12:52:36 pm
content: Quote from: floobydust on July 17, 2024, 08:10:18 pmNo, mostly 7-segment element at the bottom left corner of transparent display window, where this issue can be reproduced.The segment flashing with high contrast black color and then smoothly fading off.But I notice this issue with LCD flashing was more high when DMM was new, just out of the box.Later, when display plastic is contaminated with dust, it going to almost not noticeable, but still present...I think there is some kind of flaw DMM design, coincidence of the case design, the properties of the case material and insufficient shielding of the electronics. It leads to some induction of static electricity on the inner side of plastic window and as result it leads to some electrostatic effects on LCD and measurement part.I think the plastic transparent window of DMM works like capactior, where outer surface is one capactor terminal and inner window surface works like second terminal of capacitor. It allows to induce high electric charge on inner window surface by touching outer window surface. Or something like that.

author: LDDM
author_rank: Contributor
timestamp: July 22, 2024, 07:51:40 am
content: Small update, i've contacted Brymen via the email mentioned previously, and still waiting for a reply.I'm a bit disappointed by Brymen multimeters and how a DMM can fail like that.Regarding the test leads, i have tested other leads i have and got the same result in my test so the brymen leads are not at fault here. Moreover they have not been stretch or anything else.I bought a new multimeter and will try do diagnose my two BM869s when i receive it. It would be nice to have a Schematics but could not find one online.

author: sonpul
author_rank: Regular Contributor
timestamp: July 22, 2024, 08:29:21 am
content: I once encountered a Brumen multimeter that did not measure AC correctly. I only recently remembered this experience. I came to the conclusion that this behavior is due to the failure of the AD737 True RMS converter. The model was BM521. If I'm not mistaken, in the case of BM869s the AD636 converter is used.

author: J-R
author_rank: Super Contributor
timestamp: July 22, 2024, 09:54:00 am
content: Maybe this is a flash memory issue and some calibration points were lost. Once you get another DMM and start poking around, you could try calibrating a specific function/range to see if it makes any difference.Ian is looking for faulty test gear.Although if any BTC IC is faulty, he may not be able to repair it.Could sell them for parts. If someone has blown a hole in their PCB or cracked the display for example.

author: Fungus
author_rank: Super Contributor
timestamp: July 22, 2024, 01:20:17 pm
content: Quote from: J-R on July 22, 2024, 09:54:00 amOn two meters simultaneously?

author: joeqsmith
author_rank: Super Contributor
timestamp: July 22, 2024, 01:29:57 pm
content: Quote from: Fungus on July 22, 2024, 01:20:17 pmPossible, once details about the alignment were made public, it does seem the kiddies like to try and run through them using what ever they have laying around as a standard. And we have seen people who feel they need to have two meters reading identical to the last place.

author: J-R
author_rank: Super Contributor
timestamp: July 23, 2024, 04:13:35 am
content: The BM869s and other Brymen DMMs obviously have a small amount of flash of some kind for the calibration data as well as the mode memory. If there was a manufacturing defect of some sort the data stored there could degrade over time.