Brand new Bm869s calibration  - Page 1
Forum section: electronics / testgear

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 03:04:04 am
content: Hi,I've decided that I need to upgrade the twenty year old maplin dmm I bought as a student. It's starting to get a bit flakey and I'm also fairly sure it's quite inaccurate. This has generally not been too much of a problem. Mostly relative measurement have been good enough. I'm now needing to be able to measure various parameters to a decent accuracy as well as better precision.I'll probably get my self a decent lcr meter too.Im pretty much set on a Bm869s. This seems to be a good all round meter and should be leagues better than my current one.I've been searching round the forum about the 869s and it seems there's quite a few comments about these being far off calibration out the box.I've also read a few posts about people doing a quick calibration. I would have thought a fairly sophisticated pice of kit is needed to calibrate a meter properly beyond checking against a 5v source or whatever.Do I need to get a calibrated one, to what level, or should I get one stock and put that money towards an ltz1000 reference.Im mainly needing voltage and frequency to be super duper out of this thing. I expect to get really good capacitance (tightly matching pf caps) or resistance measurements I want an lcr meter. Probably a de 5000.I think a high end bench meter is a bit beyond budget and probably overkill for what I need so just a good solid dmm should be just the ticket.

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2021, 07:49:42 am
content: Quote from: mrdave45 on February 19, 2021, 03:04:04 amIt has a warranty...Buy it from a decent supplier, send it back for a replacement if it's out of spec on arrival.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 12:16:49 pm
content: Maybe that's answered my question. I'm not going to know of it put of spec unless it's calibrated.

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2021, 12:33:51 pm
content: Quote from: mrdave45 on February 19, 2021, 12:16:49 pmI guess if you have nothing to compare it with then you can't know. Do you know anybody else with a decent mater?Welectron will sell you one with ISO calibration certificate for 70 Euros more.https://www.welectron.com/Brymen-BM869s-Multimeter_1That won't tell you if it's gone out of spec after 6 months though, or after an "incident". For that you need to learn about building voltage references and stuff.Another option is to get yourself a second meter to compare it against. eg. TheAneng 870has good accuracy specs for the basic measurements and would be a good sanity check that costs half as much as that calibration certificate. Getgold leadstoo, they're worth it.(Plus you get a second meter, which youneed)

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 12:41:07 pm
content: I still have my maplin wg020 as a second meter.I guess I need the calibration and if I build a reference at least I can tell if the things drifting over time. Although that will presumably only tell me about voltage (maybe current) but won't say anything about frequency.

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2021, 12:51:10 pm
content: Quote from: mrdave45 on February 19, 2021, 12:41:07 pmOk,thirdmeter.Now you'l only be one meter short of being able to measure the efficiency of a voltage converter.Quote from: mrdave45 on February 19, 2021, 12:41:07 pmYou can also measure a few resistors the day it arrives then keep them in a safe place.The advantage of another meter is that it tells you about voltage, current, resistance, frequency, capacitance, everything.AFAICT by measuring on various meters, my 0.05% 5V reference is somewhere between 5.001V and 5.002V. My meters show this:

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 12:53:30 pm
content: https://www.welectron.com/DMMCheck-Plus-Multimeter-Calibration-ReferenceWhat about plumping for one of these instead.That's already calibrated. I'm guessing that the certificate for that is similar to the one I would get for the dmm but I do have something to double check against throughout the year and check all my other devices with, and presumably I could then send the refenece off every now and then the get calibrated.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 19, 2021, 01:03:03 pm
content: Quote from: mrdave45 on February 19, 2021, 03:04:04 amSeems? Please post the the links. I would like to read them for myself.Quote from: mrdave45 on February 19, 2021, 03:04:04 amIt's certainly possible that some people would have access to the level of equipment required to verify the meter. I assume this is what you are suggesting, not that they are actually aligning them.Quote from: mrdave45 on February 19, 2021, 03:04:04 amOnly you know what your needs are. I recently saved an old bench meter from salvage but it required repairs and alignment. I'm not one of the people you mention who has such equipment to calibrate, let alone align one so it's a bit of an unknown. Still, for the limited functions it has, that meter will out perform any handheld meter I have looked at. Most of my equipment is used, required repairs and over 20 years old. Doesn't hurt to look around. Maybe check some local swap meets or salvage yards.https://www.eevblog.com/forum/testgear/some-old-school-instruments-showing-how-its-done-(hp-3325a-and-fluke-8506a)/

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 01:56:54 pm
content: Quote from: joeqsmith on February 19, 2021, 01:03:03 pmhttps://www.eevblog.com/forum/testgear/aim-tti-1908-5-12-digit-benchtop-multimeter-(preview)/msg3215950/#msg3215950Maybe Ive just stumbled on the one post from the one person whos complaining about this thing.Only you know what your needs are. I recently saved an old bench meter from salvage but it required repairs and alignment. I'm not one of the people you mention who has such equipment to calibrate, let alone align one so it's a bit of an unknown. Still, for the limited functions it has, that meter will out perform any handheld meter I have looked at. Most of my equipment is used, required repairs and over 20 years old. Doesn't hurt to look around. Maybe check some local swap meets or salvage yards.https://www.eevblog.com/forum/testgear/some-old-school-instruments-showing-how-its-done-(hp-3325a-and-fluke-8506a)/Well, at the moment theres definitely no swap meets going on.I do scan ebay from time to time for bench meters but they always seem quite expensive. Unless they're in the states, then theres loads, quite cheap, but high postage plus imports plus major hassle if they turn out to be duff.If someone knows a good source in the uk for such items that would be appreciated.WHats the general consensus on something like that dmm check plus reference?https://www.welectron.com/DMMCheck-Plus-Multimeter-Calibration-ReferenceBut that would be getting one of those over the getting the calibration cert for the bm869s

author: joeqsmith
author_rank: Super Contributor
timestamp: February 19, 2021, 03:16:03 pm
content: Quote from: mrdave45 on February 19, 2021, 01:56:54 pmOnly you know what your needs are. I recently saved an old bench meter from salvage but it required repairs and alignment. I'm not one of the people you mention who has such equipment to calibrate, let alone align one so it's a bit of an unknown. Still, for the limited functions it has, that meter will out perform any handheld meter I have looked at. Most of my equipment is used, required repairs and over 20 years old. Doesn't hurt to look around. Maybe check some local swap meets or salvage yards.https://www.eevblog.com/forum/testgear/some-old-school-instruments-showing-how-its-done-(hp-3325a-and-fluke-8506a)/Quote from: mrdave45 on February 19, 2021, 01:56:54 pmWhen someone tells me "quite a few", I am expecting more than one example. But as I age, other phases like "it works" have taken on new meaning. For example, if I see "refurbished", I know it was maybe cleaned. "Tested" means it was plugged in. "Works" means no smoke came out. Now "quite a few" means one.In the context of that thread, they are talking about the 500,000 count mode. I've mentioned "quite a few" times how I have used this mode to make relative measurements. The meter is stable enough to be useful for me. For absolute measurements, I normally use the old HP. In your case, you may be trying to make absolute measurements with this sort of resolution. My advice is make sure you understand your requirements before you buy anything! The best handheld meter I have bought that was somewhat close to what I can achieve with my old HP is the Gossen Ultra. About $1000 USD. Still it was unusable out of the box. It may have been improved but you would need to look into it.I have a box that's something like the DMMCheck you are asking about. I have an APEX reference inside along with several foil resistors. There are also a few mica, Polystyrene and Wet tant capacitors. For AC, I have a simple quarts oscillator that I divide down and have direct or AC coupled. I use that box to detect is a meter is starting to fail, not as a means to calibrate them. Again, more of a relative comparison. Still, if you checked that thread I linked on the old 80's Fluke I am working on, you get an idea on the price of these resistors and how tight they are.Depending on your own requirements, something like the DMMCheck may be a good sanity test. I've never played with one.

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2021, 03:20:31 pm
content: Quote from: mrdave45 on February 19, 2021, 01:56:54 pmThose meters aren't "far off calibration", they're within spec, they're just outliers near the ends of the bell curve on the production line.They'll be few and far between but if you're unlucky enough to receive one of those then a calibration certificate or fancy DMM check will only make you unhappy. Best not to get either of those.

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2021, 03:30:23 pm
content: Quote from: joeqsmith on February 19, 2021, 03:16:03 pmI bought aused10k resistor for $7 on eBay. It can read a bit low on a cold day like today (see pic).Quote from: joeqsmith on February 19, 2021, 03:16:03 pmYep. It's fun when a meter/resistor/whatever appears to be perfect but it's really a bonus, not a garantee.The big problem is ambient temperature. Meters with lots of digits needs an internal heater for their references so they can be calibrated for a known temperature. You simply can't have that in a handheld (do you want a hot meter that chews through batteries?).

author: joeqsmith
author_rank: Super Contributor
timestamp: February 19, 2021, 04:31:21 pm
content: Quote from: Fungus on February 19, 2021, 03:30:23 pmI had started logging some temperature data while looking at the drift. I think I figured about 3deg C change in the office but it's been a bit tighter than that over several hours. I used my HP34401A as a reference to align the Fluke after repairs. So again, absolute accuracy it a bit of an unknown but I would say in the ballpark. I ran a 10K ohm on the 40 year old Fluke for about a half day. You can find the datasheet for that resistor along with the data here:https://www.eevblog.com/forum/testgear/some-old-school-instruments-showing-how-its-done-(hp-3325a-and-fluke-8506a)/msg3462878/#msg3462878

author: IanB
author_rank: Super Contributor
timestamp: February 19, 2021, 04:49:42 pm
content: Quote from: mrdave45 on February 19, 2021, 03:04:04 amIt may vary from sample to sample, but I was pretty happy with the one I received. See below:https://www.eevblog.com/forum/metrology/i-received-my-dmmcheck-plus-a-quick-test/msg1972838/#msg1972838

author: IanB
author_rank: Super Contributor
timestamp: February 19, 2021, 04:57:46 pm
content: I can't guarantee you will get the same results, but here are a couple of pictures I captured in the past:

author: radiolistener
author_rank: Super Contributor
timestamp: February 19, 2021, 05:19:36 pm
content: I don't have voltage standard, but I haveADR290E2.048 V ± 2 mV reference.And my BM867S measure it as 2.04828 V just out of the box.Now, after 3 years it is measured as 2.04826 V.I didn't performed calibration.

author: bdunham7
author_rank: Super Contributor
timestamp: February 19, 2021, 05:27:31 pm
content: Quote from: mrdave45 on February 19, 2021, 03:04:04 amI doubt that Brymen is shipping out-of-spec meters, but you shouldn't expect a 500K count meter to be exact to the last digit--it doesn't work that way. The few mentions I've seen of meters being 'off' is by people with unfounded expectations of some sort or another.If you need a certain level of precision and accuracy, you need to look at the specs and mathematically understand what is called an 'uncertainty budget'. "Super duper" is not going to cut it. For any given measurement, you need to know how far off the actual value is likely to be. This is actually a statistical issue, but it is commonly boiled down to a single value and a confidence level. So you might conclude (these are just made up numbers) that your 5.00000 volt reading actually tells you that the true value is between 4.99930 and 5.00070 with a 95% certainty. If the confidence level isn't stated, you just have the specs and you can treat those as the limits, but you don't really know how certain you are. I think of it in terms of counts--how many counts represents the limits of the meters specified uncertainty. So when I look at a Fluke 8846A displaying 10.00000 volts, I know that the specified uncertainty is +/- 29 counts with a 99% confidence level, as long as I'm within the 1 year calibration period and between 18C and 28C ambient temperature.A calibration certificate is just paper, so unless you need paperwork, I doubt it will get you a more accurate meter.As for self-calibration, you can check and verify it yourself in a limited fashion with a DMMCheck or random 'standards' like that, but this really only tells you when and if your meter is broken. The actual calibration isn't difficult if you have the standards, but in most cases I think you would just make it worse. I definitely wouldn't go trying to tweak it so that it reads exactly 5.00000 volts just because it makes you happy--that is a fools errand that will simply leave you thinking you have something that you don't.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 05:28:53 pm
content: That's brilliant, thanks all! That looks like its plenty good enough for what I need.I think Ill just order one. Still need to get an lcr meter and a logic analyser. But i guess thats for another topic.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 05:40:47 pm
content: I just wanted to be sure that I could get a meter that I could be reasonably sure that would be accurate to the mV and it looks like this will be without having to resort to the calibration cert.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 19, 2021, 06:17:50 pm
content: Personally, I would hold off until you have a better understanding of what you actually need. You would be amazed how many people write that they bought the wrong product and then want to modify it.Quote from: mrdave45 on February 19, 2021, 05:40:47 pmI too would like to have a meter that could read accurate to 1mV on a 1000V signal.Something a little more realistic, my Fluke standard attached to three meters. Note the mV reads 0.2, 1.1 and 3.4. For me, this is good enough. For you, maybe not.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 06:22:54 pm
content: sorry, i should have specified mV accuracy from 0 to 4.096V range, preferably up to 10VI would have no need to mV at 1000v range. Usually dealing with tube b+ if its not blown something up then 5% is probably good enough.

author: bdunham7
author_rank: Super Contributor
timestamp: February 19, 2021, 06:32:25 pm
content: Quote from: mrdave45 on February 19, 2021, 06:22:54 pmSo look at the example above and consider the uncertainty budget. The specs for the 869s on the 50V range are 0.03% of reading + 2 counts, so that comes out to 32 counts if I've mathed rightly. That's +/- 3.2mV, so it won't be quite 'accurate to the mV'. And in real life, the meters here are 23 counts apart, a disagreement of 2.3mV, let alone what the absolute error might be. You should calculate this for yourself on the 5V range and see if that is good enough for you.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 19, 2021, 06:37:44 pm
content: Looking at a 1V signal off the Fluke standard. Details are important.Also, just a side comment that may not pertain to you personally. I will get comments from people that will buy the BM869s as their first meter. I think the last one, the person was sending their meter back because when they picked it up with no leads attached the meter would display a voltage. ***They were comparing this where I was showing the Gossen shifting with the input terminated to 50ohms or shorted. *** This wasn't the first beginner who has sent me such a post. I tried it with mind (being winter and dry) and I was able to throw up some numbers that were far worse. I suggested I should perhaps return mine as well.I like the meter for type of electronics I play with but it may not be the best choice for a beginner. I started out learning the basics with a cheap analog meter which I used for several years. My taste for better equipment came from my hobby evolving. Had someone given me the BM869s when I started out, it would have been a complete waste. You may actually have a need for such a meter.Video showing my first meter compared with a free one.

author: joeqsmith
author_rank: Super Contributor
timestamp: February 19, 2021, 06:53:46 pm
content: Fluke standard attached to my old HP, which was used to align the Fluke meter. As I would expect, four meters yields four different answers. I also have no idea what that standard is even good for.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 07:13:24 pm
content: Ok, it looks as though, if i were to measure a 2.048v level, i would get between 2.0473 and 2.0486. Thats going to be much better than my current meter. Which is only 2000 count, much lower accuracy, and only 2 decimal places in the 20v range. Just looked at the specs, thats 1.5% +4d, I could expect to read between 1.97 and 2.12 or there abouts. In any case, a serious upgrade.Im not (quite) a beginner. I did a degree in computer systems engineering 20 years ago. Although i followed a career in music, since leaving university I got into building hifi and analogue synthesisers.Im currently developing a digital control system for an analogue poly synth and Im just finding myself needing to get a better idea of what value the components and voltages Im cobbling together actually is.Id like a better scope, but that's on hold at the moment. But being able to read voltage and frequency in particular, reasonably accurately will go a long way to help me fine tune and figure whats what. Itll be using substantially less than 1v/oct internally, probably nearer 0.4v/oct which in tern means 33mV per semitone. My current scope and meter just aren't really up to this. I want this to work reasonably well before software correction.I just haven't bought decent test equipment before and wanted some advice over getting one of these devices stock or whether i should get them calibrated. But having seen the photos of several of these next to higher end bench measurements, I fairly sure this will meet my needs.

author: bdunham7
author_rank: Super Contributor
timestamp: February 19, 2021, 07:16:10 pm
content: Quote from: joeqsmith on February 19, 2021, 06:37:44 pmThe standard was a transfer standard for obtaining a standard 10V from a Weston cell, of course. Its from the pre-JJA days when its 2ppm transfer accuracy was as good as could reasonably be expected. I find mine to still be occasionally useful, but as you are demonstrating with the 1V signal, only the 10V output works with anything other than high-impedance meters. Mine is at least as accurate as any 6.5 digit meter if you watch the tempco.

author: bdunham7
author_rank: Super Contributor
timestamp: February 19, 2021, 07:19:56 pm
content: Quote from: mrdave45 on February 19, 2021, 07:13:24 pmYou're going to use a DAC to control a VCO? That seems like the hard way...

author: J-R
author_rank: Super Contributor
timestamp: February 19, 2021, 07:25:36 pm
content: After buying both an HP34401A and a Fluke 287 with fresh calibration and data printouts and then buying Ian's excellent PDVS2mini, I did venture down the volt-nut path a small amount. I also sent out my DMMCheck Plus and a few of Doug's references from voltagestandard.com to get everything as up to date as possible and then ran through all my test equipment.With all of that in mind, it is true that the BM869s is not quite stable enough to leverage the 500,000 count mode for absolute measurements unless you make allowances for temperature drift specifically. But also the 50,000 count mode can drift a bit as well.If I calibrate the BM869s at 5V at 73F after letting it sit for 30m or so, and then the next morning turn it on at 65F, it is 6 counts low in 50,000 count mode (about 55 counts low in 500,000 count mode), while the Fluke 287 is bang on to the very last digit under the same conditions (50,000 counts). This result from the Brymen is in line with what can be seen in the thread I linked to:https://www.eevblog.com/forum/testgear/brymen-bm869-and-bm867-batch-calibration-check/Given the price difference and other aspects of those two DMMs, this is completely acceptable as long as you are aware of it.The 5V calibration point is easy to keep tabs on and if you calibrate it under the current operating conditions, the 500,000 count mode is honestly very good and completely usable in that scenario.I also did calibrate the 50V setpoint but it wasn't very far off in my case (2 counts maybe at the worst).So my suggestion is get the BM869s and compliment it with a good 5V reference that you can ship out every so often for calibration.I found DCmV to be nearly perfect, far better than spec.AC stuff is tricky. A few seconds with a function generator and you can get pretty much any DMM to read garbage, so I think that is what a scope is for?As you said, for resistance and capacitance something like the DE-5000 is a good companion.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 07:36:45 pm
content: Quote from: bdunham7 on February 19, 2021, 07:19:56 pmYes, Itll have 8 voices, so 16 vcos, plus filter cutoff and resonance, plus all the usual goodies like pwm and a stack load of vcas.How else would you control something like that? You can only use a resistor ladder off a keyboard for mono synths, and maybe a duophonic synth if youre really clever. I never really looked into that. Midi is also digital, so thatll need converting.Plus, how would you control everything else and make it patchable. The cs80 i think had duplicate rows of pots I think, but thats a very expensive way of storing patches when you can get a handful of dacs and multiplex the heck out of them.Plus you can get much more creative with digital modulation sources which really dont need to be analogue.

author: Fungus
author_rank: Super Contributor
timestamp: February 19, 2021, 08:32:19 pm
content: Quote from: mrdave45 on February 19, 2021, 07:13:24 pmI'd bet money that it willeasilybeat the paper specification of 0.03%.

author: mrdave45
author_rank: Contributor
timestamp: February 19, 2021, 08:38:59 pm
content: Thanks again, I've ordered one along with a de 5000.Just need a logic analyser now. I suspect it'll be a cheapo la2016, but will have a look at a msos but I think the one I'll really want will be far too much.

author: bdunham7
author_rank: Super Contributor
timestamp: February 20, 2021, 03:10:58 am
content: Quote from: mrdave45 on February 19, 2021, 07:36:45 pmFor an analog hybrid like you're doing, I guess I can't really think of anything. But you'll have to tune each note like a piano, right? Or is is worse, where you have to tune the equivalent of 8 pianos? I'm still trying to make a mental image of how that all maps out...

author: mrdave45
author_rank: Contributor
timestamp: February 20, 2021, 10:26:59 am
content: The hybrid nature of the instrument doesn't affect how its tubed. Pretty much all analogue vco polysynths use dacs.Youll need to setup each oscilator for correct scaling and initial pitch at a given voltage. That will mean the dacs will be pretty close. For a monosynth, that would be enough. However, with multiple osc, you will need some calibration routines. But tuning every note and making note off offset would be an automated once in a blue moon procedure. Generally, check a few specific pitches on each vco would be enough.If you look at the service manuals, all those patchable synths essentially use one dac which is multiplexed and sampled and held where it scans round 20 to 40 parameters or so.

author: mrdave45
author_rank: Contributor
timestamp: February 20, 2021, 03:21:37 pm
content: I dont suppose if any one knows whether you can log frequency against voltage with the data logger? It looks like the meter will read freq and output with VFD function but was wondering if i could graph output voltage (ac rms, preferably on a db scale, but i can always export to excel and process that) in freq domain rather than time domain to create a freq response bode plot. Just wondering whether i should have ordered the data logger after all.Thanks

author: IanB
author_rank: Super Contributor
timestamp: February 20, 2021, 07:18:46 pm
content: The meter (like almost all logging DMMs) can sample what is shown on the display at regular time intervals and record these measurements to a log (in the case of the BM869s this log is stored on a computer connected over the interface cable). Since the 869s has a dual display it can log two displayed values in each record. This would allow you to import the data log into Excel or something and then plot voltage against frequency.

author: mrdave45
author_rank: Contributor
timestamp: February 20, 2021, 08:02:30 pm
content: Amazing.That's unbelievably useful and a lot cheaper than an mso with the bode plot function enabled. And as it turns out, perfectly adequate for what I need it for.Woooooooo.I'd better order one of those interfaces too.

author: HKJ
author_rank: Super Contributor
timestamp: February 20, 2021, 09:09:46 pm
content: You may want to check TestControllerhttps://www.eevblog.com/forum/testgear/program-that-can-log-from-many-multimeters/, it is some very flexible software that can log from BM869s and a lot of other devices. The result can then be shown in charts (Log scales are possible) and/or saved as csv files.

author: Martin72
author_rank: Super Contributor
timestamp: February 20, 2021, 11:35:08 pm
content: Quote from: mrdave45 on February 19, 2021, 03:04:04 amOne of the first thing I´ve done after buying the 869 was to calibrate it external, according to ISO standard.Had cost me 79€ plus shipping and didn´t regret it so far.A dedicated calibration lab have unlike better references to calibrate like hobbyists got.

author: mrdave45
author_rank: Contributor
timestamp: February 21, 2021, 02:09:37 am
content: Thanks for the test software link, that looks like it'll be just the ticket.As I've already ordered the meter and the spec is an extra 2 decimal places at 0.02%+2d over 1.5%+4d, I'll worry about the calibration a bit later. 2000 count to 50,000 (500,000 at a push) It'll do for the time being (more than do).I knew my old meter wasn't much cop, but I hadn't realised quite how bad it was. Even though when I bought it it was one of the betters ones they had.

author: mrdave45
author_rank: Contributor
timestamp: February 24, 2021, 11:14:32 pm
content: Meter arrived today, and so far it's so much better than my old one it's not even funny. It begs one of 2 questions.1. How can meters be made this good (I know there are plenty better).2. Being as they can be made to be this good, how can they be made as badly as my old one. Which was still a lot better than many others I've used over the years.Thanks for everyone's help and input. I feel sure I've got the right tool for me at this time.I'll post some pictures once I've compared the meters on the output of my dacs.

author: larsdenmark
author_rank: Regular Contributor
timestamp: February 25, 2021, 03:46:34 pm
content: I bought my BM869s 5 years ago and the DMMChecker 3 years ago and today I get the reading in the image. I'm quite happy!

author: J-R
author_rank: Super Contributor
timestamp: February 25, 2021, 05:31:36 pm
content: Quote from: larsdenmark on February 25, 2021, 03:46:34 pmBut have either been checked against something with a current calibration? My DMMCheck Plus drifted quite a bit within the first year but has been much better since then.

author: larsdenmark
author_rank: Regular Contributor
timestamp: February 25, 2021, 09:06:22 pm
content: Quote from: J-R on February 25, 2021, 05:31:36 pmNo. Neither have been checked since purchase. I guess both could have been drifting since I got them.

author: miro123
author_rank: Frequent Contributor
timestamp: October 12, 2022, 12:16:46 pm
content: Quote from: joeqsmith on February 19, 2021, 01:03:03 pmHi Joe,see attached picture of my BM869s - 2 years old , before calibration + adjustment @ 50V range.In general my BM869s is extremally linear . The voltage reference seems to be the weakest point in terms of TC and mid-long term stability.He was off directly by the purchase but it get worst to the point that I adjusted it.I'm rising question why youtube reviewers check 50,000/500,000 meters at 20% of full scale - 1v,10,100v?