New eevblog multimeter? - Page 1
Forum section: electronics / testgear

author: iceteavanill
author_rank: Newbie
timestamp: August 12, 2020, 05:22:19 pm
content: From the EEVblog #1328 -> 3:28 I saw a 121GW Multimeter. Or at least I thought it was one until I took a closer look. Is it already announced or is something else known about that meter. I Marked all the differences I could spot in the Image below.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 13, 2020, 01:09:59 am
content: Wow, that's a nice find! It sure does appear to be a whole new design.

author: Mr.B
author_rank: Unknown
timestamp: August 13, 2020, 01:14:39 am
content: Ok Dave, tell us a story...

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 13, 2020, 02:40:18 am
content: Dave has been working on a $150 DMM. I thought the case looks a little different but this may be it. Autohold was definitely mentioned.

author: EEVblog
author_rank: Unknown
timestamp: August 13, 2020, 04:06:45 am
content: Quote from: Mr.B on August 13, 2020, 01:14:39 amFiction or non-fiction?

author: Brumby
author_rank: Unknown
timestamp: August 13, 2020, 04:07:47 am
content: I'll vote for non-fiction....

author: EEVblog
author_rank: Unknown
timestamp: August 13, 2020, 04:09:26 am
content: Quote from: Mr. Scram on August 13, 2020, 02:40:18 amIt does

author: Brumby
author_rank: Unknown
timestamp: August 13, 2020, 04:15:26 am
content: You're enjoying the tease, aren't you?

author: EEVblog
author_rank: Unknown
timestamp: August 13, 2020, 09:19:01 am
content: Quote from: Brumby on August 13, 2020, 04:15:26 amI have no idea what you are talking about.

author: iceteavanill
author_rank: Newbie
timestamp: August 13, 2020, 09:27:29 am
content: Are we gonna have to wait until 2022 for this one or is it gonna be released soon? As much as I have seen I would definitely buy that one, rather than the 121 GW.

author: BU508A
author_rank: Super Contributor
timestamp: August 13, 2020, 11:52:17 am
content: Quote from: iceteavanill on August 13, 2020, 09:27:29 amWhat do you dislike at the 121 GW?I have bought one via Kickstarter and I like it. Beside my EEVBlog BM235 it is the DMM which I'm using most on my bench.Ok, there is one thing I really do not like at the 121 GW and that's the display. Compared with the BM235 it is blurring.

author: Ranayna
author_rank: Super Contributor
timestamp: August 13, 2020, 02:09:52 pm
content: I wonder if that meter (was it talked about in the Supporters Section? I would assume so), sparked that recent discussion about the actual differences of CAT III and CAT IV ratings.Also, i can somewhat understand that people will want to abstain from buiyng the 121GW at the moment, now that a new one is apparently in the works. This one looks essentially the same, has better security ratings, and one would assume similar performance ratings.And since the history of the 121GW appeared somewhat "shaky", i can understand the wish to wait for an improved "Mark II" of the 121GW. Assuming similar or better performance, of course.And, at least on the first glance, that meter looks almost exactly like the 121GW.Looking closer though, shows that it is likely longer, there is more space between the two rows of buttons, between the buttons and the selection switch, and between the switch and the probe connectors. Additional space required for CAT IV? Also more space at the top, for the non contact tester.Regarding the second picture: The blue one is very likely the BM235. At least i can't find a contradiction, compared to mine.Don't original Bymens have a red holster? So a new, Brymen made, follow up on the BM235? But i can't find a model that would fit the silouette, since it is clearly visible in the picture that the plastic area is wider down next to the contacts and maybe also in the display area. So actually something new?Great tease

author: iceteavanill
author_rank: Newbie
timestamp: August 13, 2020, 04:01:15 pm
content: QuoteThere is nothing really that I would dislike. I just saw the new meter and the updated specs and the thinner case which I would prefer. Also for some stuff I do I need a meter with CAT4 rating(or at least I should use one).

author: Bud
author_rank: Super Contributor
timestamp: August 13, 2020, 04:01:44 pm
content: Quote from: Ranayna on August 13, 2020, 02:09:52 pmPerfect time never comes. One shall not delay to obtain a mortgage, become married, getting a child and buying a multimeter.

author: wolfy007
author_rank: Frequent Contributor
timestamp: August 13, 2020, 06:30:28 pm
content: Quote from: EEVblog on August 13, 2020, 09:19:01 amto quote short round "you cheat, you cheat Dr Jones, you" have new meter

author: TheSteve
author_rank: Unknown
timestamp: August 13, 2020, 08:09:31 pm
content: It seems it will have some magic "digital energy" inside.

author: EEVblog
author_rank: Unknown
timestamp: August 13, 2020, 11:54:21 pm
content: Quote from: Ranayna on August 13, 2020, 02:09:52 pmNope. There is no follow up to the BM235 in the works.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2020, 12:07:36 am
content: Damn could it be the 150$ meterniice if it is ? drooolllEditDamn loll

author: EEVblog
author_rank: Unknown
timestamp: August 14, 2020, 12:28:52 am
content: Quote from: coromonadalix on August 14, 2020, 12:07:36 amNope.

author: wolfy007
author_rank: Frequent Contributor
timestamp: August 14, 2020, 12:59:56 am
content: $100 meter....

author: J-R
author_rank: Super Contributor
timestamp: August 14, 2020, 03:39:58 am
content: From the carefully placed piece of tape, this is clearly a teaser.Dual display makes an appearance at 7:04.Display speed has improved, but at the expense of the bar graph. Hopefully it can be fixed or give the user some options?The red paint was smudged, not blurred in post?Separate ACV/DCV positions are nice; the frequency position seems sparse.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2020, 06:55:30 am
content: As Dave said : Nope ??

author: BU508A
author_rank: Super Contributor
timestamp: August 14, 2020, 06:56:24 am
content: will the display be better readable than on the 121GW?

author: EEVblog
author_rank: Unknown
timestamp: August 14, 2020, 07:34:40 am
content: Quote from: BU508A on August 14, 2020, 06:56:24 amI'd say yes. Digits are slightly thicker, slightly different reflective look and contrast.

author: MiroS
author_rank: Regular Contributor
timestamp: August 14, 2020, 07:59:01 am
content: Quote from: joeqsmith on August 13, 2020, 01:09:59 amThis looks like Dave did it intentionaly, otherwise model name wold not be masked. Anyway after all this horrible errors with 121GW I will not touch it until it will get stamp 'Approved by Joe' . I cannot get why some users are happy if multimeter have problem with current and voltage measerment, and why to trust that one will do any better?

author: BU508A
author_rank: Super Contributor
timestamp: August 14, 2020, 08:05:02 am
content: Quote from: MiroS on August 14, 2020, 07:59:01 amDo you have any examples for those horrible errors? I couldn't spot them in this 50-pages thread.

author: EEVblog
author_rank: Unknown
timestamp: August 14, 2020, 08:21:17 am
content: Quote from: MiroS on August 14, 2020, 07:59:01 amNope. I actually had no knowledge of or input to this design at all. It "just appeared" and will be sold under their brand. They made this branded special for me to evaluate to see if I was interested. The 121GW is not being discontinued, unless I decide to do so of course.It is a physically bigger design, higher CAT rating, better specs, true energy measurement chip, and doesn't appear to be backward compatible with my BT app.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2020, 08:55:58 am
content: Is it an 121gw evolution ? based on the same dmm chipset but added features ... and all or most of the 121gw quircks resolved ?Feels like a Brymen ??

author: MiroS
author_rank: Regular Contributor
timestamp: August 14, 2020, 10:23:44 am
content: curren measurment issue -https://youtu.be/csANYnvL32kvoltage issue - please check Joe YT chanelI am not tracing this since Joe review, maybe problems are fixed now? I wonder if this new is also having the same problems?

author: gnavigator1007
author_rank: Unknown
timestamp: August 14, 2020, 10:30:32 am
content: Quote from: coromonadalix on August 14, 2020, 08:55:58 amRange switch says no

author: Fungus
author_rank: Super Contributor
timestamp: August 14, 2020, 11:23:45 am
content: Quote from: BU508A on August 14, 2020, 08:05:02 amHow about the special shim they came up with so that the range switch actually made contact with the PCB?

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2020, 12:25:01 pm
content: Quote from: EEVblog on August 14, 2020, 08:21:17 amSo to be clear, when it becomes available it isn't sold under the EEVBLOG brand like the one shown in the video? Or did you sell the the rights to use the brand for any new products they come up with?Will your store be offering this meter or haven't you decided?

author: pascal_sweden
author_rank: Super Contributor
timestamp: August 14, 2020, 01:05:02 pm
content: Branded special, but there is no indication that it is an evolution of the 121GW or just a parallel side product of the manufacturer that has been developed completely independent!Quote from: EEVblog on August 14, 2020, 08:21:17 am

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2020, 01:08:31 pm
content: Quote from: BU508A on August 14, 2020, 08:05:02 amQuote from: MiroS on August 14, 2020, 10:23:44 amAfter Dave's comment about use of the thread, I had removed several of my comments as I understood them to be causing a lot of confusion and also clutter.To be fair, I haven't touched the meters since making the last set of videos and maybe by now they have it all sorted out. Also, at the time I had purchased the two meters from Dave's store, I was not aware he was selling old stock. Maybe the new meters improve some of the problems.Let's ignore that it appears less electrically robust now, that the mechanics can't handle the 50K cycle test and were ground to dust and that methanol strips the lettering. Let's also ignore the whole leakage, linearity problems.VA mode is still a problem but could have been addressed in the manual easy enough.The switch continues to be a problem. One of the two meters I bought had problems right out of the box with the switch. Watching the design evolve we had both double and single dimple contacts, shims, shimless, flipped shims, different plating. I don't think it was a surprise to anyone but Dave:https://www.eevblog.com/forum/testgear/new-eevblog-branded-multimeter-coming/msg1405038/#msg1405038It seems after several attempts to get the meter to reliably log to the card, it's still a problem.Autorange can cause meter not to display correctly with potential lethal levels applied.50/60hz rejection is poor. It appeared they were continuing to adjust the filters to improve the response times but the settling times suffer.Spring contacts for battery do not fit correctly.Plastic connectors seem to be failing at a high rate. Someone had just asked me again about that a couple of months back. Hopefully they are still offering replacements.The way they align the meter for capacitance is wrong. This is really odd as it was correct at one point. Once aligned it does a decent job with lower values.I don't have time to test the countless firmware updates in hopes they will stumble onto a better design. After a few years in production and still seeing many of the same problems shown with the preproduction unit, I can't see a reason to invest more time. I've looked at a fair number of meters ranging in cost and quality, they normally have all the basics sorted out.

author: HKJ
author_rank: Super Contributor
timestamp: August 14, 2020, 01:44:24 pm
content: Quote from: joeqsmith on August 14, 2020, 01:08:31 pmIf you are used to multimeter you know that everything is referenced to the common terminal. People expecting that the meter suddenly uses the current input as voltage reference are rather naive.

author: EEVblog
author_rank: Unknown
timestamp: August 14, 2020, 02:19:28 pm
content: Quote from: joeqsmith on August 14, 2020, 12:25:01 pmIt will be available under other brands as the manufacturer sees fit. It's a complement to an existing line of products.QuoteNo.QuoteI haven't decided.

author: Fungus
author_rank: Super Contributor
timestamp: August 14, 2020, 02:26:19 pm
content: Quote from: pascal_sweden on August 14, 2020, 01:05:02 pmWho says it's even the same manufacturer?

author: BU508A
author_rank: Super Contributor
timestamp: August 14, 2020, 02:34:21 pm
content: Does it have the 15V testing mode for diodes?

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2020, 04:58:34 pm
content: Quote from: HKJ on August 14, 2020, 01:44:24 pmI didn't write the manual for this meter and am only pointing out the problem with it. When I first noticed it with the draft manual and preproduction meter, I was showing the problem to Dave and I think it went right over his head. Rather than trying to understand what was being shown I just got an ear full about how I had the meter hooked up wrong. Of course the fan boys wanted to jump in on that one. So yeah, I agree many people are indeed rather naive but worse, the manual last I knew still to this day does not help this group by showing the proper way to make the measurement. Even the person who had made that video I linked stumbled into the same problem because they followed the manual. Just something to be aware of.

author: HKJ
author_rank: Super Contributor
timestamp: August 14, 2020, 05:06:53 pm
content: Quote from: joeqsmith on August 14, 2020, 04:58:34 pmI did not read the manual, but I have a couple of multimeters that can measure power and they all work the same way with the common terminal as reference. I would be very surprised if you found one that did not use the common terminal as reference and that meter would need some clear markings on it!

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2020, 05:36:11 pm
content: Quote from: HKJ on August 14, 2020, 05:06:53 pmI imagine many people will take the time to read the manual and use it for a reference when taking measurements. I would imagine in general people are going to trust the manual to have the proper procedures. Consider that not everyone is going to be an expert when it comes to making measurements with their 121GW like you are. Calling them naive is correct but doesn't help matters. Rather we took the approach to try and educate this group on how it works and how to correctly use it.

author: HKJ
author_rank: Super Contributor
timestamp: August 14, 2020, 06:19:19 pm
content: Quote from: joeqsmith on August 14, 2020, 05:36:11 pmSo the issue it not the meter and have never been (It works like any other meter with power measurement), but the manual is not good enough.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 14, 2020, 07:02:40 pm
content: Quote from: HKJ on August 14, 2020, 06:19:19 pmThe issue is if someone without your expert level of knowledge follows the users manual to make VA measurements, it will not yield accurate results. It's not my design and I did not write the manual. They certainly could design the meter to work as the manual suggests or they could just change the manual. Again when I brought it up and suggested changing how it should be wired, I was told that I had the meter incorrectly connected (in other words the manual was the intended way to wire it). IMO, I would have just changed the manual but here we are, what, three years later and it's still a problem. I hadn't thought about it until KainkaLabs had posted that video where they were following the manual and coming up with incorrect results.https://www.eevblog.com/forum/testgear/eevblog-121gw-discussion-thread/msg2191287/#msg2191287The meter I use doesn't have a common reference but its designed to measure the mains.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 14, 2020, 09:52:20 pm
content: this thread should be merged with the 150$ meter thread?

author: EEVblog
author_rank: Unknown
timestamp: August 14, 2020, 11:04:53 pm
content: Quote from: coromonadalix on August 14, 2020, 09:52:20 pmNo. This is NOT the $150 meter I've been talking about for some time.

author: EEVblog
author_rank: Unknown
timestamp: August 14, 2020, 11:25:05 pm
content: Quote from: MiroS on August 14, 2020, 10:23:44 amFirst time I have seen that video.Just tried to replicate it with the same AC currents and couldn't. Although I was using a low voltage source instead of mains. So

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 15, 2020, 06:17:21 am
content: This issue could be with a particular firmware version , anyway it is far from finished ... and never will be

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 15, 2020, 07:41:23 am
content: Quote from: EEVblog on August 14, 2020, 11:25:05 pmThat's a very strange setup. His explanations are practically incomprehensible,so I assume it's a sort of dimmer module and a LED bulb containing an SMPU in series, probably creating a very irregular ac-current waveform with a high crest factor / high DC superposition.The hardware / software of the GW121 has definitely big weaknesses with superimposed DC on AC signals, which seems to be the case here, again.Therefore, in such situations, an overrange condition is not detected properly, and then a clipping occurs in too a low range, exactly what this guy demonstrates when he uses a fixed, upper range.So that's nothing new, and has been discussed in length already. (superimposed DC on AC in ACV mode, w/o giving a high voltage warning)Frank

author: EEVblog
author_rank: Unknown
timestamp: August 15, 2020, 09:37:58 am
content: Quote from: Dr. Frank on August 15, 2020, 07:41:23 amYep, not much I can do without more details. Likely related to the large DC offset voltage issue I would assume.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 15, 2020, 12:54:28 pm
content: I wrote Scott to see if he would post a scope shot of the current and maybe a CSV file. I've suggested he place that information here.I did try to replicate it as well using the Arb. These included DC biased waves and such. Scott has the early version of the meters. If I still can't replicate what he shows using my released meter, I'll try it with the proto.

author: floobydust
author_rank: Super Contributor
timestamp: August 15, 2020, 04:25:02 pm
content: I find this a common fault with single chip DMM's. Firmware writers, youtube testers- all miss it. It's why I have 35 year old clunker DMM's in my collection because they have no firmware and never lie to meI use this test jig/circuit to flush out the men from the boys. You will be surprised at the results.Inject say 250mVAC 1kHz sine into a DMM on ACV. Add variable DC offset of either polarity and see what "true RMS" numbers you get. Either the readings are nonsense, or the autoranging screws up, or both. (frequency measurement doesn't work, as expected without zero-crossings).My theory, when you have significant DC component on an AC waveform, it seems to be when the A/D converter pegs or clips for that range, which gives erroneous readings. Because you're looking at the true-RMS DSP value, it will not show a (DC) saturated A/D with the HPF. The autoranging algo doesn't see a need to range up and thus gets stuck. I would look at the A/D raw number too- but this halves the sample rate.MESTEK DM-100C, ANENG AN8008 is a bit weird. Boot up, no DC offset, ACV 250mVAC 1kHz reads fine.AN8008 - switch on with anything over +/-3VDC offset, ACV goes berserk hunting for a range and reading odd numbers. Switch on ACV with no DC offset, then slowly ramp up to 20VDC and it reads fine throughout.DM100C - add anything over +15/-17VDC offset, goes berserk hunting for a range and reading odd numbers or 0.000 if saturated.Once a meter sees the big offset, I did see it "remember that" - if I disconnect the signal so the DMM autoranges down, then reconnect the AC+DC signal, I saw it behave differently from then on, compared to a cold boot. Sigh.

author: HKJ
author_rank: Super Contributor
timestamp: August 15, 2020, 06:14:44 pm
content: Youtube testers may miss it, but I don't:https://lygte-info.dk/info/DMMReviews.htmlI call it "True-AC" in my reviews (Yes, it is a silly name, but I had to use something that was short).My tests are usually done around a couple of hundred volts where I use AC on DC range and DC on AC range and a combination of AC and DC with AC>DC and DC>AC.As you conclude many meters fails on this.

author: Kean
author_rank: Unknown
timestamp: August 15, 2020, 06:56:30 pm
content: The polarity switch on that schematic looks messed up.

author: floobydust
author_rank: Super Contributor
timestamp: August 15, 2020, 08:33:30 pm
content: Quote from: Kean on August 15, 2020, 06:56:30 pmFixed, I was half awake.Quote from: HKJ on August 15, 2020, 06:14:44 pmStill a bit confusing because there are two measurements - I have a bench DMM withAD637AD536Athat has True RMS AC+DC, or AC-only selectable. AC-coupled I would call the measurement "true-AC".Here it's just bad software engineering, the edge cases are not tested. As I see it, A/D clipping happens and the DMM's firmware bungles the range choice under certain, select conditions.

author: dcac
author_rank: Frequent Contributor
timestamp: August 15, 2020, 10:05:29 pm
content: Quote from: Dr. Frank on August 15, 2020, 07:41:23 amI wonder if this particular case has something to do with the max4238 amplifier. Looking at the disassembled firmware and the 121gw schematics - the only thing different between 5.0000mA and 50.000mA range - seems to be 5.0000mA is being passed through the 4238. So:5.0000 mA = max4238_x10 -> hy3131_OP1_x10 -> (RMS)50.000 mA = hy3131_OP1_x10 -> (RMS)And max4238 seem to have lower BW than the OP:s in hy3131. GBWP = 1.0 MHz vs '2.0 MHz'.But of course without knowing more of this particular current waveform it’s all just guesswork what’s really happening.

author: EEVblog
author_rank: Unknown
timestamp: August 16, 2020, 12:59:34 am
content: Quote from: HKJ on August 15, 2020, 06:14:44 pmHigh voltage DC offset values are known to cause issues, particularly so with some meters that have combined AC/DC range switch positions.

author: wizard69
author_rank: Super Contributor
timestamp: August 16, 2020, 04:06:38 am
content: Quote from: EEVblog on August 14, 2020, 12:28:52 amNOPE???That meter has a lot of features I could use. So is the EEVBlog about to issue a new range of tools? this gets more and more interesting especially with the blurred out text..

author: wizard69
author_rank: Super Contributor
timestamp: August 16, 2020, 04:13:59 am
content: Quote from: EEVblog on August 14, 2020, 08:21:17 amSome of us would find those features very interesting!!!!!

author: joeqsmith
author_rank: Super Contributor
timestamp: August 16, 2020, 04:57:24 am
content: I had hoped Scott would have chimed in. No doubt that the 121 would have problems, but I could push it enough to make my two normal meters disagree by a fair margin. Guessing it's something like this but would have liked to have seen the waveforms. Oh well.

author: EEVblog
author_rank: Unknown
timestamp: August 16, 2020, 05:02:56 am
content: Quote from: wizard69 on August 16, 2020, 04:06:38 amI'm sure it does. But the 121GW doesn't even sell for close to US$150 and you expect an even higher end version (true energy measurement, triple display, higher CAT rating etc) to sell for $150?Again, this meter has absolutely nothing to with the $150 class meter I have been talking about for the last 9 months, that is a different meter. I have placed an order for those and will have them soon enough for those interested in a $150 price class meter. Sign up for my newsletter and you might even get it cheaper than that upon release.

author: Scottjd
author_rank: Frequent Contributor
timestamp: August 16, 2020, 06:45:32 am
content: It took me a second to find this thread, no one put the thread link in the video comments. I was looking under the other 121GW threads. I wasn’t expecting this to be under a “New eevblog multimeter” thread.I tried to send you a DM to find the thread, but I got a message that the DM was blocked.That shelly module as I called it in the video (“Shelly1PM”) that I was trying to read the current from has since been installed in the walls. I have another one arriving but shipping has been delayed these days so I don’t know when I will get it. I might have a normal Shelly1 but I will have to look for it.As for the current measurement on the scope, I don’t own a differential probe. The best I have is a Hantek CC-65, the specs on it are not the best.Yes, this is the original 121GW from the kickstarter. One was a replacement from Dave after the switch shunt fix for the switch didn’t work on the original one. The other one is the original one that I later fixed after seeing Daves video on a BM235 with the case tolerance causing a switch issue. So I dug it out and tweeted the case to get it working again. It original one also had an issue with resistance readings, but everything else seems to work within spec.Quote from: joeqsmith on August 16, 2020, 04:57:24 am

author: Scottjd
author_rank: Frequent Contributor
timestamp: August 16, 2020, 06:53:36 am
content: This is a Shelly1PM module, or Shelly as I called it in the video. It’s a remote relay trigger with WiFi for turning on/off switches in the wall. It doesn’t do any dimming. It’s a smart home IOT device.The crest factor according to my Fluke 298 is about 5.0 if I recall correctly. I think you asked this in a comment on the video.The 121GW did this when trying to read the current of a Shelly1PM, its a relay smart module that also measures the current being used back to the app. This was found when trying to see the difference in current being used between a Shelly1 standard module and a Shelly1PM.It wasn’t anything to do with the LED nightlight I grabbed from the kids bathroom. The LED light was just to demonstrate that once the load went over a certain range the 121GW would flip over from the 5mA range to the 50mA range.The Shelly1PM I had wired would use about 12mA to 13mA without the relay activated and the 121GW showed 4.88mA, not yet at the top of the 5mA range.When I turned on the relay it would use about 17mA to 18mA, you will see the 121GW max out at the top of the 5.2mA range, but still wont flip into the next range.When I added the additional load of the LED bulb for another 2.5mA this was enough to force the 121GW to change ranges and display it correctly.Originally I had a regular LED light plugged in that uses about 10mA, but was curious to see if a smaller load would also be enough to flip the range on the 121GW.Quote from: Dr. Frank on August 15, 2020, 07:41:23 am

author: _Wim_
author_rank: Super Contributor
timestamp: August 16, 2020, 06:55:59 am
content: Quote from: joeqsmith on August 16, 2020, 04:57:24 amAnd what was the correct value? Was the Brymen or the Fluke closest or where they all quite a bit off?

author: dcac
author_rank: Frequent Contributor
timestamp: August 16, 2020, 07:53:50 am
content: Quote from: Scottjd on August 16, 2020, 06:53:36 amThe 5mA range does not 'max out' at 5.2mA - it will actually read up to 5.4999mA before it needs to change range.

author: dcac
author_rank: Frequent Contributor
timestamp: August 16, 2020, 07:55:52 am
content: So it’s not really a question of 121gw ‘getting stuck’ (as mentioned in the video) and wont auto-range. But instead it’s reading the waveform ‘wrong’ and showing too low value in the lowest 5.0000mA range. But in the next range 50.000mA it’s reading it correct.According to the manual ACA measurements is specified for 45 to 1000 Hz.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 16, 2020, 10:05:35 am
content: If a shitty Aneng meter is showing correctly it's not a bandwidth issue ... maybe the 10x op-amp is not up to the task and is latching or something

author: Scottjd
author_rank: Frequent Contributor
timestamp: August 16, 2020, 11:39:34 am
content: I did find another Shelly1PM and a standard Shelly1, I thought I saw them when we rearranged the office the other day.Attached is the capture from the scope from the PM version since that’s the one I used in the video. Keep in mind that I am using a Hantek CC-65 that is rated for the lowest reading of 20mA although I have seen this go down to 5mA before it fails.I tested this with looping the wire on the clamp two and three times and had the same waveform without the loop.I also confirmed this Shelly1PM exhibited the same behavior using the 121GW, as did the standard Shelly1.I am also including two screen shots.The one with 11.5mA is just the shelly being powered.The one showing 20mA (actual is 18.5mA) is just the shelly engaging the relay without any light bulb.

author: ralphrmartin
author_rank: Frequent Contributor
timestamp: August 16, 2020, 12:28:47 pm
content: Quote from: HKJ on August 15, 2020, 06:14:44 pmUnless I am overlooking something, I don't see a "True AC" column on that page. Maybe you could add it - it would be useful, rather than having to go through the reviews one-by-one.

author: dcac
author_rank: Frequent Contributor
timestamp: August 16, 2020, 02:43:23 pm
content: Quote from: Scottjd on August 16, 2020, 11:39:34 amThanks for the current traces. It seems fairly simple to reproduce the problem with 60Hz square wave and 12% dutycycle (roughly simulating that current waveform). If DC offset is then increased or lowered - in 5mA range something seems to go into saturation and the wrong value is shown.It really seems like it is the max4238 causing it. But not the OP it self but the fact that the signal gets amplified 10x. Further investigation is needed why something further down the line doesn't seem to like this.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 16, 2020, 04:29:10 pm
content: Quote from: Scottjd on August 16, 2020, 06:45:32 amIf you log onto your Youtube account, then select customize channel, video manager, comments then select "held for review" or "likely spam". My guess is you have a few in there by now. Links will typically be picked up by one of the filters.I was using a pulse to create the picture I uploaded, very similar to what you show. This doesn't surprise me that the 121 has a problem with it. As you can see, in my particular case even my other meters differ.

author: Scottjd
author_rank: Frequent Contributor
timestamp: August 16, 2020, 04:52:34 pm
content: Quote from: joeqsmith on August 16, 2020, 04:29:10 pmI check the comments every few days since I block an extensive list of words from my security days that I created a while back, and yes yours got blocked by the URL. Youtube Studio usually shows a number next to the published, held for review, or likely spam comments but not this time. This time I had to go into held for review to see the new comments held. They keep changing studio, errr.Thanks for the URL, at least I did find it. I guess you didn’t need the CSV file, it looks like you already replicated it.Scott

author: joeqsmith
author_rank: Super Contributor
timestamp: August 16, 2020, 05:40:37 pm
content: Quote from: Scottjd on August 16, 2020, 04:52:34 pmYeah, don't get me started on YT. My only saving grace is that I don't use it often.I tried running 100 or so different symmetrical waveforms to compare the 121 against the Fluke 189 and didn't run into any problems so I assumed it was some sort of large one sided spike. I had put this program together (attached) many years ago to drive my arb. It really needs to rewritten but instead, it gets mod after mods and's a real mess. The last thing I did was port it to Windows 10, so no more Win XP VirtualBox. Some things work, others don't.But it's really flexible.

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 16, 2020, 10:29:42 pm
content: Quote from: Scottjd on August 16, 2020, 11:39:34 amHello Scott,many thanks for your oscillograms! Very interesting.So inside these modules are small and simple SMPUs, which create small square wave current pulses, which have a high Crest factor, like the problem in ACV, with high DC superimposed.The 121GW, like many other DMMs, calculates the RMS by fast digitizing and directly calculating the sum of the squared values of the samples.The amplitude of about 55mAppof these pulses in the idle case would normally create an overrange, as this is 10 times the 5mA range, which is for some reason not detected by the HY3131, or by the SW.Dave has built in an additional x10 amplifier to feature 'low burden' on the current ranges, and the HY3131 provides additionally two selectable x10 stages. So I assume, that an undetected analogue signal clipping inside the HY3131 occurs. 55mApover 1 Ohm shunt give 55mVp, times 10 once gives 550mVp, and then calculated in the 50mA range to give about 12mArms. That's clipped to a display of about 5mA in the 5mA range, i.e. factor 2.5 low, i.e. one of the amplifiers,or the A/D is clippingat about 2.2Vp.This makes sense, as the HY3131 is powered from3.3V3.6V,and AGND is at about 1.2V, so the positive margin is 2.4V.So as the fast A/D should be able to handle high Crest factiors, i.e. high peak amplitudes, there should be a window comparator (in SW?) to detect any pulses at its input higher than2V+/-1V, or so, to range up in that case, although the RMS value does not exceed the current range yet. .. I've tried to figure out from the datasheet, from the configuration manual, and from the circuit diagram, how to detect such an overload condition, but could not find out, how to do this properly.Frank

author: floobydust
author_rank: Super Contributor
timestamp: August 16, 2020, 11:49:23 pm
content: Am I the only one that can't get excited about a new EEVblog-branded multimeter in light of the 121GW issues? I don't understand why it seems uncared for.If the ACV autoranging bug is severe - failure to display hazardous live invalidates 61010 approval, this is a safety function. If it were me, I would be lighting a fire under the programmer's ass to get this bug fixed asap. A manufacturer having awareness of a safety problem and not acting or warning on it, lawyers advise it's a very bad situation. I don't know what the problem is, but UEi might be interested.I could be wrong or overreacting here, but I have expectations of a brand and this is no fun.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 17, 2020, 08:29:20 am
content: Same here and i find the related threads slowly drifting away ... i dont need to see testo meter brand or fluke t6 clamp meterI'm in need of at least 2-3 new meters at my job, and i need an autohold badly ... i make tons of measurements and the old flukes we have are getting tiresome to use ...I had very high expectations for the 121gw ... maybe too high ?

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 17, 2020, 08:30:56 am
content: Fool me once shame on you , fool me twice shame on meIf the same company is involved that can't test and do a relative simple firmware right , I would never buy again . And there are some hardware issues too , like weak rotary switch

author: Marco1971
author_rank: Contributor
timestamp: August 17, 2020, 09:45:58 am
content: Quote from: Dr. Frank on August 16, 2020, 10:29:42 pmHi, 121GW uses a "True RMS to DC" converter i.e an Analog Devices AD8436https://www.analog.com/media/en/technical-documentation/data-sheets/AD8436.pdfFluke 87V uses an Analog Device AD737Jhttps://www.analog.com/media/en/technical-documentation/data-sheets/AD737.pdfOnly analog computations not in the digital domain.Marco1971

author: EEVblog
author_rank: Unknown
timestamp: August 17, 2020, 10:02:10 am
content: Quote from: coromonadalix on August 17, 2020, 08:29:20 amMy new $150 class meter has AutoHold, might be an option. Shouldn't be too far away, but I've said that before...

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 17, 2020, 10:09:04 am
content: Quote from: Marco1971 on August 17, 2020, 09:45:58 amThe conversion principle is not relevant in the end, concerning the clipping of the OPAmps.Anyhow, I also first stumbled across this RMS chip AD8436, but it is AC coupled only, and its input label RMS_IN seems not to be connected anywhere else in the schematic, so maybe this IC is a placeholder only?I'll have a look, if it's really assembled inside the 121GW.Frank

author: Marco1971
author_rank: Contributor
timestamp: August 17, 2020, 10:15:53 am
content: Quote from: Dr. Frank on August 17, 2020, 10:09:04 amThe conversion remain in the analog domain not in digital as you stated before.IC17 on mainboardhttps://lygte-info.dk/review/DMMEEVBlog%20121GW%20UK.htmlMarco1971

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 17, 2020, 10:52:26 am
content: Quote from: Marco1971 on August 17, 2020, 10:15:53 amYou're correct.. I also found this missing label RMS_IN.Then the explanation of all this mess is easy..For this low burden current measurements, in the 5mA range, the shunt voltage is amplified by 10 by U8, MAX 4238, then again by 10 by the OP1 of the HY3131, where the clipping occurs. Then the signal goes directly to the RMS converter U17, and its DC output is measured by HY3131.Therefore, there is no physical option to detect this clipping of OP1, as the AC signal is routed outside the HY3131.That's a real HW design flaw.The ACV problem has different root causes.Frank

author: coromonadalix
author_rank: Super Contributor
timestamp: August 17, 2020, 02:23:06 pm
content: Would an op with an agc gain applied to it could correct this clipping problem ??Or simply put the low burden option is a burden in the circuitry 10x gain with another 10x gain is kinda too much ?

author: Kleinstein
author_rank: Super Contributor
timestamp: August 17, 2020, 04:05:38 pm
content: I don't think the extra gain should be a problem here - if at all there could be a problem with the reference point used for the amplification of the max4238. However this should normally be correct the other side of the shunt. For the DMM chip it makes no difference wether the signal come directly from the shunt or from the extra amplifier. The max4238 should only give a small output signal like 0.2-0.5 V max, comparable to a normal shunt signal. So this OP should not run into saturation. However the signal may be a little larger than from a normal shunt and leave the common mode range of the input - something that the normal protection would prevent directly at the shunt.There may be a tiny chance that the x10 from the max4238 and x10 from the DMM chip together may start oscillating under certain condition via a feedback through the virtual ground.The maximum crest factor (peak values compared to RMS) may be limited by the design / level the RMS chip is driven too. So the design balance may be more towards low noise / low maximum crest factor instead of higher permitted crest factor at the cost of more noise and drift. Especially currents may show a high crest factor. Ideally (e.g. new meter) there would be detection of exceeding the peak levels and switch to the next larger range or a special high crest factor mode.

author: dcac
author_rank: Frequent Contributor
timestamp: August 17, 2020, 06:29:21 pm
content: I measured the maximum output swing of OP1 in hy3131 and it’s almost rail to rail (0V to 3.6V).And AGND in ACA mode is set to 1.8V. So relative to this it equals a swing from -1.8 to +1.8 volt. And with the 100x amplification (max4238+OP1) that equals -18mV to +18mV maximum over the 1 ohm shunt.So any current waveform exceeding this range will definitely be clipped by OP1 before it reaches the AD8436 RMS converter.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 17, 2020, 08:21:00 pm
content: Then this is a basic design fault , the current is allmost never a sine wave but pulses and you should give enough headroom without posibility of clippingBut there is also an issue with detection of shorter pulses ... it's not switching in the next range 50mA as the true-rms value is greater than 5mA .So for clipping with 10x op-amp the experiment should be done with true-rms values bellow 5mA to see what crest factor is admisible and if in real life is measuring ok .

author: Kleinstein
author_rank: Super Contributor
timestamp: August 17, 2020, 09:08:37 pm
content: Some 18 mV / mA maximum would be rather small maximum crest factor of some 3.5 before clipping starts at the top of the 5 mA range. This is especially poor without a warning.The RMS/DC converter could in principle support a crest factor of at least 10 (not sure this also works with the rather low supply). So it's a question of how to set the ranges.A SW fix could be to already step to the 50 mA range at some 2 mA, not just at 5.5 mA, effectively reducing the 5 mA range to 2 mA or 2.5 mA in automatic mode.A HW fix would be reducing the gain before the RMS chip and have more after.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 17, 2020, 10:09:06 pm
content: Even if the true-rms converter has poor crest factor capability it's not near as bad as clipping the signal upstreamso removing the part above a crest factor altogether

author: floobydust
author_rank: Super Contributor
timestamp: August 17, 2020, 10:28:58 pm
content: I see software fixes possible, where you switch an A/D to the raw input and do peak detection to look at the crests and model if the op-amp is near overloaded by pulses. You're not using the (slow) A/D samples for the actual measurement but for the autoranging decision. Aliasing would happen at high frequencies, but for mains frequencies this is doable.It's hard to tell with the indecipherable HY3131 datasheet that is six years old, she's a headbanger

author: joeqsmith
author_rank: Super Contributor
timestamp: August 18, 2020, 02:18:44 am
content: Quote from: _Wim_ on August 16, 2020, 06:55:59 amSorry, I wasn't ignoring you but wasn't sure so I repeated the test, this time using an even lower duty cycle to exasperate the problem.The three meters were again placed in series and their total resistance measured. These were placed in series with a 50 ohm resistor. I assume the Arb is 50ohms and the cables are zero. Applied a 60Hz, 0-5Vpeak pulse with a duty cycle of 0.005% or 83us wide.I calculate the current to be 6.62988mA.121GW; 0.5432 ACmAFluke 189; 1.954mA AC+DCBrymen BM869s; 6.6535mA AC+DCThat's asking a lot out of any meter. Normally I would be using a scope to make this sort of measurement. As part of evaluating the 121, I had made a video showing how fast some of the meters I have are when looking at short pulses like this. I have a couple of CEM meters that are very fast when using the voltage mode. I'm not sure how it would do with current.*****Just noticed.... I had cleaned up my Arb software today. That should read AC+DC Amps. The AC+DC to the left would be voltage. Maybe there are other mistakes. Best to check my math...

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 03:39:10 am
content: I just tried this short pulse current measurement. The 121GW is again somewhat range dependent on this. If you fix the range it's much better.Also compared the "upgraded" design and it reads higher than the others on short pulses for some reason.Also compared the new $150 class meter.The Keysight U1282A seems to perform the best, but new $150 class meter beats the BM879 when the pulse gets shorter like, see one photo with 30us, it holds up better.All the meters including the 121 are about the same above about 200us.I haven't measured or calculated the "exact" expected value.

author: maginnovision
author_rank: Super Contributor
timestamp: August 18, 2020, 05:02:34 am
content: That's on par with what I've seen from my five keysight meters, including the small offset for AC current.

author: MiroS
author_rank: Regular Contributor
timestamp: August 18, 2020, 07:16:10 am
content: Dave short pulse case has nothing to do with 121GW problem with bad current measurement. I think people here are right , this is design HW flaw which probably can be masked in software, by the cost of slowing down 121GW.Other than that I think that this new one may have a problem as well. At first look instant zero looks like a good result, but I checked my trusty FK28II , Tektronix DMM, Brymen , FK289 and all they work the same way for your pulse test. I believe it is so for a reason, so if that new one is not doing as all respected multimeters than I would rather think that this new one has a problem somewhere or is using a new kind of technology which is rather at very, very small probablity in my opinion.In context of new multimer, all this flaws with 121GW and qestion if this is secure multimeter - maybe we have here someone from 'certification company' to share some insides - is there any chance to recognize problems like we see with 121GW in certification process ?It got me thinking that certificate by X is not the same as certificate by Y, if so that this will make me sad. Dave which company will certificate this new multimeter?

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 08:21:47 am
content: Quote from: MiroS on August 18, 2020, 07:16:10 amI just wanted to repeat the test Joe did because I thought it would be interesting.But isn't the problem video in question about some sort of pulsed current?

author: MiroS
author_rank: Regular Contributor
timestamp: August 18, 2020, 08:45:25 am
content: Quote from: EEVblog on August 18, 2020, 08:21:47 amI do not think so. I think people here are right regarding HW design flaw. That has nothing to do with pulse width, but pulse high.I am at opinion that BM869 works OK, and instant zero in this new multimeter may indicate the other problem. I edited my previous post with this and other remarks/questions.

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 08:54:29 am
content: Quote from: MiroS on August 18, 2020, 07:16:10 amThe only "Certification" in multimeters is 61010 et.al, and that is related to safety, not really to performance aspects. And even then when you start talking about this kind of pulse stuff, it's almost infinite. You could have 0-99% duty cycle, pulse widths from naf all to whatever, against every frequency across the whole bandwidth across all signal levels across all the ranges. The permutations are insane, and that's just for pulse current that we are talking here let alone all the other functions.No such magic certification exists.

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 08:56:42 am
content: Quote from: MiroS on August 18, 2020, 08:45:25 amWhy would a meter displaying zero current instantly when you remove said current "indicate a problem"?If anything, a meter that continues to display current when there is no current would be the problem, surely? Just saying"well, that's how they all work" is not much of an argument.

author: MiroS
author_rank: Regular Contributor
timestamp: August 18, 2020, 09:15:44 am
content: Quote from: EEVblog on August 18, 2020, 08:56:42 amI think if you measure RMS than if voltage is 100V at time t0, and zero at t1 than RMS over AC period will be not zero right? Otherwise I would say instant zero is instantaneous value, not RMS.That may be something like that. To be sure I would need to refresh in my head metrology lectures and do some math. The other reason may be that AC in grids is never very clean, so maybe safer is to average AC for loger time that to show instantaneous value? or filtering is doing causing that delay ? Anyway instant zero may indicate a problem somewhere in my opinion.

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 09:45:51 am
content: Quote from: MiroS on August 18, 2020, 09:15:44 amIt's not actually "instant", meters typically sample 3-5 times per second, so say a 200ms period.If you want to do software averaging over several sampling periods, that's fine, it's typically a feature called "smoothing" on Fluke's for example. Also AVG mode can be used.But if you remove the current then why wouldn't you want your meter to read zero within the next sample? Let's say within 2 samples because it could have been removed mid-sample.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 18, 2020, 10:08:27 am
content: If you do some of theses test on a few bench meters with faster sampling rate what will happen ? will they catch the pulse(s) better ?The norm with many meter brand is 3-5 times a sec, never saw an hand held meter with faster sample rates, and my 28-29 gossen are at 2 - 2.5 a sec ... wich i find slooooooooow as hell.Sadly i dont have a sig generator to do some of theses tests

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 18, 2020, 10:10:49 am
content: Hi group,This 'tail' that is being observed is part of the RMS conversion process. TheMis for mean (or average). The signal has to be averaged over time, this implies a low pass response.The tail isn't unique to the current ranges. I took a Fluke 85 III and attached a wire to pin 6 of the AD737 RMS converter.I put the meter in AC volts and fixed the range at 4VI applied a burst 1000 cycles of 1kHz sinewave to the input.Here are the waveforms:The cyan trace is the inputThe blue trace is the output on pin 6 of the AD737The time base is 400ms/div.If I look at the Analog devices datasheet:I find graphs like this one. It basically says the accuracy improves if you do more averaging.More averaging is a slower transient response.There are similar graphs on the AD8436 datasheet:They even have this one, this is similar to the measurement I made:[ Specified attachment is not available ]A long 'tail' might be a good thing ...Regards,Jay_Diddy_B

author: coromonadalix
author_rank: Super Contributor
timestamp: August 18, 2020, 10:17:13 am
content: ok you need a good hw and a good fw equilibrium, even if sometimes it misse its objectives, too fast or too slow

author: MiroS
author_rank: Regular Contributor
timestamp: August 18, 2020, 11:17:20 am
content: We would be more clear on this getting chipset name in this new multimeter.Dave is it possibile to share with us chipset used in this new multimeter?

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 11:24:27 am
content: Quote from: MiroS on August 18, 2020, 11:17:20 amFor the $150 meter, I do not know, it's custom branded.The other "new" meter is the same HY3131 used in the 121GW.

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 11:25:30 am
content: Quote from: Jay_Diddy_B on August 18, 2020, 10:10:49 amYes, that is to be expected, but 10+ seconds?

author: joeqsmith
author_rank: Super Contributor
timestamp: August 18, 2020, 12:11:41 pm
content: I had written Brymen about the how their filters worked in the 235 and assumed their response would have been added to the manual. I'm sure that post is still around.I tried running the CEM DT-9939. I thought this meter may hand the short current pulses much better than the Bymen based on how well it does with short voltage pulses but it does not appear to be the case. It's a little better than the 189. It's about as slow as the Keysight shown in Dave's video when removing the current.

author: EEVblog
author_rank: Unknown
timestamp: August 18, 2020, 01:15:46 pm
content: Quote from: joeqsmith on August 18, 2020, 12:11:41 pmI've asked Brymen again, so will see what they say.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 18, 2020, 01:45:47 pm
content: Quote from: EEVblog on August 18, 2020, 01:15:46 pmFrom 2017Quote

author: coromonadalix
author_rank: Super Contributor
timestamp: August 18, 2020, 02:28:18 pm
content: We need at least 8 readings and up to have a good averaging ?? time to add an oversampling measurement lollor cram an 34401a or keithley 200x or any other good bench dmm in a hand held device loll

author: Kleinstein
author_rank: Super Contributor
timestamp: August 18, 2020, 03:19:55 pm
content: The RMS chips need some time for averaging. With the analog chips this is usually not synchronized with the AC waveform and an infinite time pulse response filter. With the usual RMS chips one has to find a balance between reasonable fast response and added errors, especially at lower frequencies (e.g. 50 Hz and below).AFAIK the RMS chips are somewhat different in the way they do the averaging and with some solutions the time constant depends on the amplitude - this can give slow settling going down.Another possible problem to cause slow settling is if they use an electrolytic capacitor with high dielectric absorption. The filter cap often needs to be quite large (e.g. > 1 µF) so that electrolytic caps are not unusual, but there are different types to choose.There are a few different options on how to implement the RMS conversion. Especially the higher end meters may use some kind of digital sampling instead of classical analog RMS. This way one could have a different type of filter, especially an FIR type filter or signal synchronous measurement.So it is possible to have fast response and an accurate reading.Another odd point of most analog RMS chips is that the bandwidth depends on the amplitude. With low amplitude they tend to get slower. At the upper end there may be a slew rate limit that can also cause an error with a square wave signal.With electronic equipment it is not unusual to have a more pulse like wave form and one not allays known this upfront. So a good DMM should work with such waveforms. It is not just SMPS, but already rectifier and filter cap.

author: MiroS
author_rank: Regular Contributor
timestamp: August 18, 2020, 05:22:43 pm
content: [quote author=EEVblog link=topic=250310.msg3193994#msg3193994 date=1597749867For the $150 meter, I do not know, it's custom branded.The other "new" meter is the same HY3131 used in the 121GW.Thanks Dave.I guess that this new is SANWA, if so than this will be Brymen chipset, it will be very interesting to compare SANWA and Brymen.I may be wrong of course, but who else than Fluke and Brymen have its own chipset those days

author: floobydust
author_rank: Super Contributor
timestamp: August 18, 2020, 07:10:04 pm
content: ACV and DCV subroutine from another manufacturer using the same Hycon chip. I've been laughing about it for daysThose skilled in the art can suggest a better approach to 0.0Code:/***DMM_DGetAvgValue****Parameters:** int cbSamples - The number of values to be used for the average value** uint8_t *pbErr - Pointer to the error parameter, the error can be set to:** ERRVAL_SUCCESS 0 // success** ERRVAL_DMM_VALIDDATATIMEOUT 0xFA // valid data DMM timeout** ERRVAL_DMM_IDXCONFIG 0xFC // error, wrong current scale index****Return Value:**double** the DMM value, or** NAN (not a number) value if errors were detected**Description:** This function computes an average value corresponding to the DMM value** returned by DMM_DGetValue, for the specified number of samples.** The function uses Arithmetic mean average value method for all but AC scales,** and RMS (Quadratic mean) Average value method for for AC scales.** If there is no valid current scale selected, the error is set to ERRVAL_DMM_IDXCONFIG.** If there is no valid value retrieved within a specific timeout period, the error is set to ERRVAL_DMM_VALIDDATATIMEOUT.** It returns INFINITY when measured values are outside the expected convertor range.** When no error is detected, the error is set to ERRVAL_SUCCESS.** The error is copied on the byte pointed by pbErr, if pbErr is not null.** When errors are detected, the function returns NAN.***/double DMM_DGetAvgValue(int cbSamples, uint8_t *pbErr){uint8_t fValid = 1;double dValAvg = 0.0, dVal;int i;int idxScale = DMM_GetCurrentScale();uint8_t bErr = DMM_ERR_CheckIdxCalib(idxScale);uint8_t fAC;if(bErr == ERRVAL_SUCCESS){fAC = DMM_FACScale(idxScale);if(fAC){// use RMS (Quadratic mean) Average value for ACfor(i = 0; (i < cbSamples) && fValid; i++){dVal = DMM_DGetValue(&bErr);fValid = (bErr == ERRVAL_SUCCESS) && (dVal != INFINITY) && (dVal != -INFINITY )&& !DMM_IsNotANumber(dVal);if(fValid){dValAvg += pow(dVal, 2);}}if(fValid && cbSamples){dValAvg /= cbSamples;dValAvg = sqrt(dValAvg);}}else{// use normal (Arithmetic mean) Average value for other than AC.for(i = 0; (i < cbSamples) && fValid; i++){dVal = DMM_DGetValue(&bErr);fValid = (bErr == ERRVAL_SUCCESS) && (dVal != INFINITY) && (dVal != -INFINITY )&& !DMM_IsNotANumber(dVal);if(fValid){dValAvg += dVal;}}if(fValid && cbSamples){dValAvg /= cbSamples;}}}if(bErr != ERRVAL_SUCCESS){dValAvg = NAN;}if(pbErr){*pbErr = bErr;}return dValAvg;}

author: MiroS
author_rank: Regular Contributor
timestamp: August 19, 2020, 05:28:57 pm
content: I spent a few minutes with sheet of paperand easy tests, it looks that instant zero may bring a problem - limiting factor is low frequency AC range, precision , but the most annoing is screen fluctuation.I seems like cheaper multimeters may give instant zero, like Fluke 17B+, that one is instantly showing 'zero', but at some costResult is rock solid for BM869s and badly fluctuationg for 17B+ for low frequency . I do not have cheap 'multimeters' for further tests.BM869s is at lower side 5Hz, 17B+ - 40 Hz, so that new one showed by Dave may have probably higher low AC frequency in spec.Tests conducted staring 1Hz and and up.Dave can you check spec for low AC frequency for voltage/current mesurement for this new multimeter / do some tests?

author: Kleinstein
author_rank: Super Contributor
timestamp: August 19, 2020, 07:53:12 pm
content: The older AD736 RMS converter has the odd point that settling slows down when the reading is low, so it is inherently slow going back to zero. The newer AD8436 used in the GW121 does not have this and may be faster without compromising so much on the low frequency of higher crest factor performance. It could be just the choice of RMS converter that makes the difference.It is usually a balance between response speed and accuracy - for a handheld meter I would often prefer fast response over a little more error at lower frequency. The higher end bench meter can even have the option to chose between 2 modes.In theory the software could compensate some of the slow end of the settling.

author: floobydust
author_rank: Super Contributor
timestamp: August 19, 2020, 08:37:06 pm
content: Post #66bug is a mains-frequency 1/2 wave rectified waveform. The DMM has plenty of time to notice it needs to range up.Looking at usec pulses is intellectually titillating but have you heard of the oscilloscope?It's no wonder this stuff will never get fixed as we move on to the next shiny object.

author: EEVblog
author_rank: Unknown
timestamp: August 19, 2020, 11:23:33 pm
content: Quote from: floobydust on August 19, 2020, 08:37:06 pmThis is not a half wave rectified mains waveform:

author: EEVblog
author_rank: Unknown
timestamp: August 19, 2020, 11:35:11 pm
content: Quote from: MiroS on August 19, 2020, 05:28:57 pmNew meter is 3dB down at 2.5Hz. BM869 is only a smidge better, but it goes crazy jumping around at anything under 3Hz.New $150 meter doesn't like anything below 10Hz.

author: floobydust
author_rank: Super Contributor
timestamp: August 19, 2020, 11:39:44 pm
content: Quote from: EEVblog on August 19, 2020, 11:23:33 pm5ms/div, looks like half-wave rectifier current to me. Fullwave is 2x f_mains or 100Hz/120Hz.

author: EEVblog
author_rank: Unknown
timestamp: August 20, 2020, 12:00:57 am
content: Quote from: floobydust on August 19, 2020, 11:39:44 pmYes, but it's not a half wave rectifiedwaveshape.

author: Wytnucls
author_rank: Super Contributor
timestamp: August 20, 2020, 07:11:22 am
content: Half wave crest factor is equal to 2. This wave form has a crest factor of 4~5, which is beyond the capability of most multimeters.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 20, 2020, 07:33:07 am
content: The pulses look like half wave rectification with a filter cap. So about what to expect for a very cheap low power SMPS input. So the current waveform in not that unusual anymore and a good multimeter should be Ok with this. I would not mind a few percent of error, but a grossly wrong reading (e.g. 5 mA instead of 18 mA) is quite a bit far off and more like a bug in the GW121.A relatively small filter cap would cause some error on high crest factor signals, bit this should be only a few percent at 50 Hz. For a current signal a crest factor of 5 is not that unusual and the RMS/DC coverter would in principle allow this (e.g. 5 % error at a crest factor of 10 - though it depends on the details).From what I have read here, a 100 fold amplification and thus 500 mV (RMS) full scale after the amplifier seems to be too much to allow high crest factor signals. No sure if SW could fix/reduce this by doing automatic range switching already earlier (e.g. at 2 mA / 20 mA). I would prefer a trustworthy reading over extra counts in the AC mode.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 20, 2020, 05:32:08 pm
content: Of course crest factor can't be an excuse if in the video an Aneng meter is showing correctly ... what are we talking about ?As I said in many many cases the current is in pulses , that's how a diode bridge rectifier + filter cap works . This is absolutly basic

author: Kleinstein
author_rank: Super Contributor
timestamp: August 20, 2020, 06:55:50 pm
content: It looks like most handled DMMs have specs with a crest factor of < 3. I have found something as bad as <1.5 when near the full scale, for some Fluke meters (e.g. 117), though not clear if this applies to voltage readings only or also to current readings. With current readings a higher crest factor is very common - so it would be nice of the meter would work there too. The AD8436 chip allows for a crest factor of 10 with slightly higher error - so in principle it would be possible to build for a higher crest factor.The cheaper meters with 2000 counts and thus a 200 mV range may have it easier to allow a higher crest factor (peak values) than meters with a 500 or 600 mV range to get a few more counts. If limited to a rather low crest factor (probably around 1.5 for the GW121 near the end of range) one should at least have a warning when exceeding this limit. One usually does not know the crest factor up front, so some tolerance to a higher crest factor can be an important factor.

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 20, 2020, 08:01:00 pm
content: Folks,this weakness of the 121GW has nothing to do with Crest factor in first instance. This instrument simply has no proper overload detection for its (internal) OpAmps, at about +/- 1.6V, or so. Therefore, signal clipping occurs, which falsifies of course the RMS calculation.Overrange / uprange only occurs, when the measured (clipped) RMS value exceeds the chosen range.This obviously happens in ACI and ACV.This overload detection requires a fast sampling of the amplified signal, sort of peak-window detection, which is not implemented. Even in ACV it's not implemented, what makes me wonder. The fast internal A/D could serve this purpose.Better DMMs feature a separate fast window comparator for that.So you have to live with this weakness and may anticipate manual upranging, when you expect 'difficult', non-sinusoidal signals.Frank

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 20, 2020, 08:48:57 pm
content: Hi,To build on what Dr. Frank said.I scanned the 121GW manual to see what it had to say about crest factor.The manual echoes the Analog Devices specifications for the AD8436 as having CF of 10.I am not sure if the crest factor is preserved in the design, because it would require a lot of headroom, without clipping, in the amplifier stage in front of the AD8436.Crest factor is the peak / RMSThe Fluke 289 DMM has a crest factor of 3 at full scale and increases to 5 at mid-scale. This make sense because there is more headroom at mid-scale.You can find tables on the internet that illustrate various crest factors.A 5% duty-cycle square wave has a crest factor approximately equal to 4.5A 1% duty-cycle square wave has a crest factor of 10Most waveforms that you measure will be lower.Regards,Jay_Diddy_B

author: Kleinstein
author_rank: Super Contributor
timestamp: August 20, 2020, 09:04:34 pm
content: Quote from: Dr. Frank on August 20, 2020, 08:01:00 pmThe crest factor is just a different way to express the peak voltage. With a 500 mV full scale range at the RMS converter, the 1.6 V limit of the amplifier would allow for a crest factor of about 3 when at the full scale. With more there will be clipping and thus a possibly large error, not just the slowly increasing error from the AD8536 data-sheet, that is valid with a smaller amplitude (e.g. 200 mV or 300mV with a higher supply voltage).Specs for the peak value at something like 3 times nominal range may be less confusing. This would imply a limit for the crest factor of 3 at full scale, allowing more at lower voltage.

author: EEVblog
author_rank: Unknown
timestamp: August 21, 2020, 06:34:16 am
content: Quote from: Dr. Frank on August 20, 2020, 08:01:00 pmYes. Kane have had a lot of problems with the HY3131 chipset, and have specifically noted that there are issues with using both internal (fast and slow) ADC's at the same time and/or switching between them.They have even sent engineers to Hycon several times to try and resolve this sort of stuff, but it seems there are just inherent limitations in the chip. Particularly so when AC and DC share the same switch position, which is the issue with the volts autoranging. That's not unique to Kane either, other brand meters that share AC/DC volts knob position can also have issues with detection of autoranging with DC offsets on AC signals. It's why the new design meter uses separate AC and DC switch positions.

author: EEVblog
author_rank: Unknown
timestamp: August 21, 2020, 06:37:20 am
content: Quote from: CDaniel on August 20, 2020, 05:32:08 pmThe waveform show is very different to a full or half wave bridge rectified signal. The one shown obviously has some form of zero volt crossover switching that makes it switch hard on, so gives a sharp turn on current edge. Why does everyone keep trying to equate it to a basic rectifier?

author: 2N3055
author_rank: Super Contributor
timestamp: August 21, 2020, 06:51:44 am
content: Quote from: EEVblog on August 21, 2020, 06:37:20 amTo me that looks like some SCR phase controlled switching waveform..

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 07:17:24 am
content: Hi,Here is a quick model of a 'wall wart' power supply, a very typical line frequency application:The waveforms are:The Crest Factor, peak / rms, for the input current is 2.7 This is a very typical application.Regards,Jay_Diddy_B

author: rattnallen
author_rank: Contributor
timestamp: August 21, 2020, 07:19:37 am
content: To me it looks like the current into the smooting capacitor, i.e. the current into a normal diode bridge rectifier with a smoothing capacitor after the bridge...That is something almost every cheap gadget that you connect to the mains nowdays will show.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 07:54:55 am
content: Hi,Here is a model for phase control with a resistive load, a typical Triac light dimmer:The waveformsAnd the measurements:At 10oThe Crest factor is 7.4 but the peak current is low.This is probably okay unless the DMM auto-ranges to a range that cannot handle the peaks.This is probably the highest crest factor found in 'normal' applications.Jay_Diddy_B

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 21, 2020, 07:55:33 am
content: Quote from: Jay_Diddy_B on August 20, 2020, 08:48:57 pmIt's getting even more complicated, as inside the 121GW in ACI mode, the RMS converter is AC coupled only.I experimented a bit with asymmetric current pulses, i.e. positive square wave pulses only, generated by a variable duty cycle pulse generator and a V/I converter, applied to the 121GW, BM869, KS34465A and a HP3458A in series, and often got about 4 different results, due to different coupling and RMS conversion methods. Of course the over range/clipping indication was also different.That all was quite confusing, i.e. what would really be the meaning of the displayed RMS measurements, even on these other instruments which have proper (over-) ranging functionality. Let aside the 121GW, on all other DMMs it's always very difficult to find out from specification or the manual, how the AC signal is coupled internally and how the RMS conversion is really accomplished.Frank

author: Marco1971
author_rank: Contributor
timestamp: August 21, 2020, 07:57:38 am
content: Quote from: Jay_Diddy_B on August 20, 2020, 08:48:57 pmLTC1968 True RMS to DC converter used by Fluke 287/289https://www.analog.com/media/en/technical-documentation/data-sheets/1968f.pdfMarco1971

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 08:10:45 am
content: Hi,Analog Devices (LTC) provides this data for the LTC1968:This is relative to 200mV output, which is mid-scale.They use SCR waveforms, the same as modeled earlier.This matches the Fluke 289 performance.Regards,Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 08:25:36 am
content: Quote from: Dr. Frank on August 21, 2020, 07:55:33 am1+I don't think it is possible to AC couple an asymmetric waveform and measure the RMS .Simple example:10V dc with 2.8mV p-p sinewave ripple.RMS is approximately 10VIf you ac couple you read 1mV RMSRegards,Jay_Diddy_B

author: HKJ
author_rank: Super Contributor
timestamp: August 21, 2020, 08:45:04 am
content: Quote from: Jay_Diddy_B on August 21, 2020, 08:25:36 amThat is exactly what good multimeters do. You get separate AC and DC values and you may also have a AC+DC that combines them.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 21, 2020, 09:19:56 am
content: At least in theory the AC coupling does not cause much problem. The total RMS including the DC part would be the square root of the DC reading squared plus the square of the AC coupled RMS reading. This general formula also applies to asymmetric waveforms. The AC coupling and limited bandwidth can be a problem with peak to peak readings, as this is sensitive to phase shifts between the different frequency components. Phase shifts can have quite some effect before the amplitude changes much.The LTC1968 RMS converter is different from the classical ADxx36 ones in using a kind of SD ADC inside. This may lead to relatively hard internal clipping, while the analog nonlinear circuit is more like slowly increasing errors first. The more analog AD8436 is better behaved in this respect. However this does not help of the amplifier in front (or the absolute value part of the circuit) does hard clipping.Chances are the GW121 will be much more tolerant to a high crest factor signal more in the center of the range.A maximum crest factor of 1.5 like in the Fluke289 near the end of scale limits this to essentially sine only (already crest factor of 1.4). Compared to this the GW121 should be still good.

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 21, 2020, 10:46:40 am
content: Quote from: EEVblog on August 21, 2020, 06:34:16 amHi Dave,I again dug deeper into the schematic and the HY3131 datasheet. Latter already has a programmable, fast window comparator on board, both lower and upper limits are programmable everywhere inside the VDD, VSSrange, which is intended for monitoring the output of OP1 .. can't understand why this could not implemented for ACI, at least.Should also work for this ACV + DCV problem.Yes, the ACV signal is routed over OP1 again to the external RMS converter.Therefore this comparator should be able to detect any overload conditions also.Frank

author: dcac
author_rank: Frequent Contributor
timestamp: August 21, 2020, 12:58:28 pm
content: Quote from: Dr. Frank on August 21, 2020, 10:46:40 amIn AC modes the comparator is already used for the frequency measurement. Though ACI does (currently) not seem to show frequency so here it should be possible to free the comparator and, as you describe, use it for an out or range detector. Upper and Lower reference can conveniently be set at 0.1V and 3.5V - so if OP1 output exceeds this range it’s time to change range upwards or to show OFL.Correction:ACI does actually show frequency.And there does not seem to be any other route to the hy3131 counter when measuring AC. The CNT pin seems only connected in Hz-Duty modes.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 21, 2020, 01:33:12 pm
content: AC current measurement is identical to AC millivolt or at least the chipset producers intended to be made in this way , so should't be any issues detecting over range inside HY3131 if the firmware is working correctly , even if the input waveform is a pulse , has DC offset and so on . Or we have an issue with voltage too ?The external x10 amplifier could clip the signal at some point , but the firmware should be able to switch ranges by then .

author: dcac
author_rank: Frequent Contributor
timestamp: August 21, 2020, 02:04:22 pm
content: Yes possibly a problem in ACV and ACmV too. Also here OP1 is used as 1x and 10x buffer - so it can be clipping the waveform before is reaches RMS chip.Dr. Frank is correct the comparator presents a possible firmware solution - but as it is now it is already used for the frequency measurement in AC modes.But to detect AC+DC voltages in DC mode and select the appropriate range - which it failed to do in Joe's test - should be doable without losing other functionality.

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 21, 2020, 02:14:15 pm
content: Quote from: dcac on August 21, 2020, 02:04:22 pmLast point requires ultimately an overrange detection, that's not safely possible with DC mode conversion, I think .. last chance would be use of the fast A/D, but I'm not sure about its input range limitations and its capability to detect high count / low count conversions.Otherwise, better sacrifice the 2nd display for frequency to have a safe and properly working AC functionality.Frank

author: dcac
author_rank: Frequent Contributor
timestamp: August 21, 2020, 04:33:21 pm
content: Quote from: Dr. Frank on August 21, 2020, 02:14:15 pmI measured the lower frequency limit in AC mode to be about 2Hz. So perhaps the comparator can alternately be used both for clipping detection and frequency - if you switch between the two at i.e. 1 sec intervals. One drawback would be a less responsive frequency display - if frequency changes it will take a moment to show.But 1 sec period should enough time to 'sense' the input signal for potential clipping. The comparator has a latching output and 2Mhz BW at 40mV P-P, which seems more than fast enough for what we dealing with here.Implementing something like this is however a more substantial rewrite of the firmware - more than I think we seen in previous updates.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 21, 2020, 09:52:26 pm
content: I checked in mV range and surprise or notfor simple square wave 500mVpp 100Hz , no DC offset like Dave said it is the cause , it is not autoranging right if the duty cycle is below 9% . It is showing something ( clipped ) in the 50mV range and is showing correctly in the 500mV range only if you manually switch it .I used a Fluke 187 for comparison , and it is fooled in the same way just below ~2% duty cycle .Autoranging detection from around 10% duty cycle is pretty bad and probably the cause for not measuring the current right . For currents it is much more visible as the pulses have low duty cycle ( of course) ...I would speculate that the reason is the slow / inefficient firmware and not hardware

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 10:35:36 pm
content: CDaniel and the group,If the signal is DC coupled the RMS value= pk x ( duty_cycle)0.5for a 10% duty-cyclepeak 500mVThe correct answer = 158mVIf it is AC coupledYou calculatepos = +PK x (DUTY_CYCLE)0.5neg = -PK x (1 - duty_cycle)0.5Total = ( pos2+ neg2)0.5= 150.02 mVThe Crest Factor = pk /rmsCF (dc coupled) = 0.5 / 0.158 = 3.16CF (ac coupled) = 0.45 / 0.15 = 3.0I am not sure that you should be measuring a unipolar square wave on the AC range.If you measure on the DC rangeyou should measure the pk x duty_cycle = average voltage = 50mVBut you may also run into clipping if the auto range is on.Regards,Jay_Diddy_B

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 21, 2020, 10:46:36 pm
content: Why you assume it's unipolar ?... I used alternating square wave to be clear , centered on 0V , that is what I meant when I said no offset .And yes , the correct value is around 150mV but 121GW is showing about 52mV in 50mV range at 9% duty cycle . With 1% duty cycle more added ( 10%) will over range and measure correctly in 500mV range

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 11:01:45 pm
content: Hi,If you are dc coupled and +/- 250mV, symmetrical about ground.The correct answer is 250mVIf you are ac coupled the and the signal is +/-250mV wrt ground theThe correct answer is 150.02mVThis is because the ac coupling removes the dc offset.Jay_Diddy_B

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: August 21, 2020, 11:14:58 pm
content: Hi,I set my HP8116A to generate 100Hz 10% duty-cycle High level 500mV Low Level 0VI connected a 50precision termination (0.1%) and measured the voltage with a few of the meters that I have in the lab.Here are the results:Datron 1281I don't have an HP3458A. I have to make do with a Datron 1281Fluke 85 IIIFluke 289HP 3457A on the AC rangeHP3457A on the ACDC rangeThe HP8116A isn't super accurate or stable.But all of these readings are close to what they should be.Regards,Jay_Diddy_B

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 22, 2020, 05:33:13 am
content: Very well , this is the result to be expected , but 121GW will show something about 3 times lower in the 50mV range as long as the duty cycle is below 9% , then will jump and show ~150mV.As I said a Fluke 187 will autorange correctly from 2% duty cycle . This meter is similar 50,000 counts and has 50mV and 500mV rangesThis makes all the difference when measuring current from a diode rectifier + filter cap wich has low duty cycle

author: EEVblog
author_rank: Unknown
timestamp: August 22, 2020, 06:03:47 am
content: Quote from: Dr. Frank on August 21, 2020, 10:46:40 amAll I can tell you is that they have extensively looked into solving this, including I believe sending someone to Hycon to liase with them about it, and they could not come up with a solution for the AVC ranging issue.

author: EEVblog
author_rank: Unknown
timestamp: August 22, 2020, 06:06:27 am
content: Quote from: joeqsmith on August 21, 2020, 02:46:11 pmIf you don't have anything productive to add Joe please stay out of the thread.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 22, 2020, 07:42:10 am
content: It looks like the auto-ranging is based on the RMS reading and done in software. So it should at least be possible to change the level when the next higher range is used. I would prefer it to step up to the next range a little earlier, possibly well before the actual maximum. So instead of some 5.4 mA the level may be already at 3 mA. This would reduce resolution / number of counts, but in the AC ranges one does not really need 50000 counts, as the accuracy is not that high anyway. The manual ranging would still give the full 5.5 mA range. I would expect the limits to be relatively easy to change, unless this goes all the way to ADC overload.For voltage readings the high crest factor / clipping is not very likely, but for the current ranges a pulsed current waveform is quite common. The SCR and rectifier with a large filter cap case both look similar. So it would be nice to tolerate at least something like a crest factor of 5, even if this comes at a price (reduced range).For AC readings the frequency is often known, so I would not give so much weight to the secondary frequency reading. The display of the crest factor like with the fluke 289 would be often more useful. The external RMS converter would not permit this, but the hy3131 internal digital RMS would allow this. If the hardware allows it would be nice to also have the option to use this RMS version. Here peak values and thus the crest factor would be available. In some respects the digital RMS should also have other advantages: faster response, better stability, more accurate at the low end (e.g.< 1% of full-scale), detection of clipping and amplitude independent bandwidth, though lower overall BW.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 22, 2020, 08:05:37 am
content: No , it is not using the true-rms chip for autoranging , because in DC range for pulses has to take the same decisions .'It is using the internal comparators or the fast ADC , the one showing the bargraph .Now we can make all kind of suppositions , but an owner of Keysight U1282A with HY3131 or other similar meter could tell very quickly if the chip itself is "sluggish" or the 121GW implementation sux

author: dcac
author_rank: Frequent Contributor
timestamp: August 22, 2020, 08:37:07 am
content: Yes it is using the true-rms value from AD8436 for auto-ranging. And that’s why we’re having this problem. AD8436 have no idea if signal got clipped by hy3131 and hy3131 have no idea about the signal level before it samples the AD8436.The ‘fast ADC’ is not used at all in 121gw with current FW. The bargraph gets its data from the main AD1 converter - the same that samples the AD8436.But speaking of duty-cycle, currently in AC modes only the frequency is calculated but I think all data is there to also calculate the duty-cycle. If so no new configuration for the hy3131 is needed and the comparator can keep its function for frequency. And instead measured RMS voltage plus the measured duty-cycle is used to decide when/if to change range.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 22, 2020, 09:43:52 am
content: I can"t belive it is so bad ... How to use slow true-rms converter for autorange

author: PA0PBZ
author_rank: Super Contributor
timestamp: August 22, 2020, 11:28:06 am
content: Quote from: Jay_Diddy_B on August 21, 2020, 11:14:58 pmDG4062, terminated in 50 Ohm:34461A: 150.9BM235: 146.61241B: 150.687 III 150.0Fluke 45 150.6K. 197 150.63478A 150.5PM2528 149.2

author: MiroS
author_rank: Regular Contributor
timestamp: August 22, 2020, 11:56:40 am
content: Quote from: EEVblog on August 22, 2020, 06:06:27 amJoe did much, much more that anyone else here in order to make 121GW better

author: joeqsmith
author_rank: Super Contributor
timestamp: August 22, 2020, 02:51:40 pm
content: Quote from: MiroS on August 22, 2020, 11:56:40 amThanks

author: tautech
author_rank: Super Contributor
timestamp: August 22, 2020, 05:02:30 pm
content: Quote from: joeqsmith on August 22, 2020, 02:51:40 pmYes, a bit ironic that the famous TE reviewer that's picked holes in equipment for the last decade is not happy when the heat is turned up on his product.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 22, 2020, 05:22:15 pm
content: I would say its a learning curve, fw and hw issues, and maybe some checks who where never been tought or situations we may never have/face while using a meter.The newer model may benefit from this, and all 121gw related problems ... the 121 was a first in many things ...And i'm sure Dave had put lots of efforts in this project.And the forum brings lot of ideas, some do's and dont's, some cold, some hot loll

author: Dr. Frank
author_rank: Super Contributor
timestamp: August 22, 2020, 07:09:10 pm
content: Quote from: joeqsmith on August 22, 2020, 02:51:40 pmSorry, no, I don't think so.At first I dislike such malicious comments/video like you, Joe, made against Dave, or in general were made against anyone else in this forum in this mood.2nd, making destructive tests which mostly exceed the usual test standards, is no constructive way to improve any DMM.3rd, many other contributors have also identified many (more) failures and weaknesses in SW and HW of the 121GW.4th, identification and complaining about these failures alone, especially often in a similar malicious way, for me does not give rise to improvements.To my gut feeling, many different , other contributors have really made constructive proposals, which partly went into Engineering Changes and led to substantial improvements.Dave, please keep on with your good work, and also your willingness to openly discuss such interesting design problems.Frank

author: floobydust
author_rank: Super Contributor
timestamp: August 22, 2020, 10:51:02 pm
content: Despite joeqsmith's harsh style and trollish tint, he is a constant reminder that it's not all unicorns and rainbows with the product. Instead of sweeping it under the carpet.While nobody expects perfection or the crushing of Fluke's balls,I expect a spirit of improvement- which seems to be happening at a frustrating, minimal amount with the multimeter. The schematic is years old? Sorting out the input protection changes? No fun. On the other hand, Dave has given personal support 1000x that of any manufacturer. So it is a bit crazy making.

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 12:57:28 am
content: Quote from: tautech on August 22, 2020, 05:02:30 pmI could easily have instantly shut down any comment or discussion over the years, but have I ever done so? No,never.But what I won't tolerate is people, regardless of the contributions they have made, continue to constantly make snide remarks and derail and pollute otherwise useful technical threads. There are several people that constantly do that, and they are continuing to do it again in this thread.

author: tautech
author_rank: Super Contributor
timestamp: August 23, 2020, 01:44:25 am
content: Quote from: EEVblog on August 23, 2020, 12:57:28 amYou'd be a hypocrite if you did.QuotePut yourself in their position Dave, they've invested good coin in one of your products and been disappointed in it for one reason or another of which AFAIK some potentially dangerous issues are still not addressed.Snide remarks as you put or 'pointers' to flaws of many products and brands abound in this forum with advice of what to apply a 40' barge pole to are frequent yet subtle warnings about your products should be exempt ?This facet of the forum is allowed to prosper to the point where members signatures denigrate brands and you turn a blind eye to it like control of it could be conceived as moderation of free speech.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 23, 2020, 06:13:59 am
content: Well , nobody forced David to design and put his name on a multimeter to earn some extra money ... so he can expect all kinds of reactions if his multimeter is not as good or has obvious flaws not resolved for years . Everything discussed here has a technical reason after all ...

author: BU508A
author_rank: Super Contributor
timestamp: August 23, 2020, 09:11:53 am
content: Criticism is okay as long as it is done in a constructive manner.Some contributions here are probably based on facts but the undertone is sarcastic and in some cases hostile.I don't like this.I'd really appreciate it, if we could come to a good technical solution. Even the discussions around these issuesare very useful or do I have to remind you, that learning is based in a very lot cases on flaws, issues and mistakes?So, please come down, have a cup of coffee or tea (or imagine sitting together at a nice place and have a good cold beer / drink)¹take a deep breath and assume, that the person on the other side is really nice.Thanks.¹I'll bring some cakes.

author: Wytnucls
author_rank: Super Contributor
timestamp: August 23, 2020, 09:31:04 am
content: No meter is perfect, even from major brands like Fluke, Gossen and Keysight, as most of you have discovered.Nobody was forced to buy that multimeter. If you think that Dave is not doing his utmost to iron out its perceived flaws, put yours up for sale and move on.I don't see any used 121GW available on eBay or anywhere else at the moment, so have to assume that most owners are happy with their purchase.

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 09:33:02 am
content: Quote from: BU508A on August 23, 2020, 09:11:53 amIt's not just that, that's ok, but when they do it over and over and over again, sometimes forhundreds of posts, it has to stop.People who are unhappy with their meter have been offered a full refund, but they don't take me up on the offer, instead it seems to be some kind of sport to them to continually pollute the forum threads about it. And it's just happening again with this one.

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 09:41:23 am
content: So what's the deal with this new meter?As I said, it "just appeared", I had absolutely no input to it nor knowledge of it. If you want to know why they did it, it seems like they want to extend their 500 series line with a higher end meter. Predominately sold in China I believe, but could be in other markets.http://www.kanetest.com.cn/category.php?id=36http://www.kanetest.com.cn/goods.php?id=109They decided to take the 121GW and put it in a bigger case, up the CAT rating, add true power measurement, motor measurement etcAlso, it's supposed to solve the DC offset issue by using separate AVC and DCV ranges.The exiting line already had Bluetooth.They kept stuff like the SD card logging, low burden, but dropped the 15V diode mode.I had no idea they even had these existing designs.

author: Wytnucls
author_rank: Super Contributor
timestamp: August 23, 2020, 09:53:14 am
content: There is a UEi DM525 with bluetooth and power measurement already ($260.00).Is it the same 6000 count meter in a different case?

author: BU508A
author_rank: Super Contributor
timestamp: August 23, 2020, 10:04:33 am
content: Quote from: EEVblog on August 23, 2020, 09:41:23 amThat's a pity. This is one of the features I'm using a lot (checking LEDs and Zener diodes).How much space is this part occupying on the board? Did they removed it for cost reasons?

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 10:12:47 am
content: Quote from: BU508A on August 23, 2020, 10:04:33 amI think it was going to be troublesome for their CAT IV rating, so probably decided to just drop it to be safe. This seems to be a more "electrical" oriented meter. But it's spec is better than the 121GW, so

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 10:14:26 am
content: Quote from: Wytnucls on August 23, 2020, 09:53:14 amYep. UEi is one of Kane's brands. Would be the same meter I'm sure.So it's almost certain they will sell this new one in the US under the UEi brand.

author: 2N3055
author_rank: Super Contributor
timestamp: August 23, 2020, 10:17:45 am
content: Quote from: BU508A on August 23, 2020, 10:04:33 amI have Metrix meter that has normal and zener mode (27V /10 mA) in diode test mode..I use it all the time. I do a lot of LED displays and it allows me to test full segment of 5 serialy connected LED in one go..I wouldn't want to give up that function..It's a shame they dropped that, that was, to me and my work, more important than low dropout...

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 10:46:31 am
content: Quote from: 2N3055 on August 23, 2020, 10:17:45 amWow, which model is that?

author: Wytnucls
author_rank: Super Contributor
timestamp: August 23, 2020, 10:48:38 am
content: MTX3293/329226V 10mA :

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 10:55:28 am
content: Quote from: Wytnucls on August 23, 2020, 10:48:38 amMetrix still make meters?

author: Wytnucls
author_rank: Super Contributor
timestamp: August 23, 2020, 10:57:05 am
content: https://www.chauvin-arnoux.com/en

author: EEVblog
author_rank: Unknown
timestamp: August 23, 2020, 11:02:27 am
content: Quote from: Wytnucls on August 23, 2020, 10:57:05 amUrgh, THIS is a Metrix.Oh boy did I lust after one of those when I first saw the centerfold in the magazine

author: 2N3055
author_rank: Super Contributor
timestamp: August 23, 2020, 11:07:26 am
content: Quote from: Wytnucls on August 23, 2020, 10:48:38 amYes, MTX3293..Very nice advanced meter. Goes through batteries like a Russian tank, but they are rechargeable...

author: 2N3055
author_rank: Super Contributor
timestamp: August 23, 2020, 11:10:27 am
content: Quote from: EEVblog on August 23, 2020, 11:02:27 amYep that was very good meter.... They used them a lot (in addition to Fluke) in local oil refineries (yes plural, we had two in the area...) ..

author: BU508A
author_rank: Super Contributor
timestamp: August 23, 2020, 11:33:17 am
content: Current models are:MTX 3292BMTx 3293BHere is a technical datasheet:http://www.ics-schneider.de/media/pdf/products/MTX3290_3291_3292_3293_Datasheet_EN.pdf

author: coromonadalix
author_rank: Super Contributor
timestamp: August 23, 2020, 11:38:49 am
content: They cost as much like Gossen .... loll I just hate the leads position on the top.The old mx5x series are software calibrable, ask Chauvin Arnoux and in some cases "if not already available on their web site", they will sent it to you, like they did

author: coromonadalix
author_rank: Super Contributor
timestamp: August 23, 2020, 11:54:38 am
content: Quote from: 2N3055 on August 23, 2020, 10:17:45 amIt's a 121gw rip off in a senseI think Dave made a pointThis thread as gone long enough, the 150$ meter thread has gone down, and at first i was not sure if this thread was about the 150$ or something else, came down to the 121gw design issues and there are existing/pinned threads about it

author: rsjsouza
author_rank: Super Contributor
timestamp: August 23, 2020, 12:26:17 pm
content: Quote from: tautech on August 23, 2020, 01:44:25 amThe continuous bashing is par for the course; the snide, gratuitous and sarcasm are par for the course. But so as pushing back or retorting the actors that are propagating this. That will become the norm for years to come. It is how I see this back-and-forth between Dave and his most fervent public detractors.Regarding bashing, I am pretty sure you can relate to that, tautech, as you also had very heated discussions with more than one member that spent spent real money on a product and keeps (or kept) bashing the brand furiously against the manufacturer's terrible attitudes and design flaws - even as recently as the SDS1104X-E release and its missing capacitors.Despite I agree with the frustration brought with the high expectations that a meter from Dave would "rule them all", as I mentioned in another thread, the 121GW had an unprecedent open design and major changes (such as the main processor) were made and publicly reported. Throughout this process I was also releasing a product and could relate to how difficult it was to have such public scrutiny during the design phase.If anything can be learned from these discussions is that the 121GW benefited greatly from this "public shaming".

author: chronos42
author_rank: Regular Contributor
timestamp: August 23, 2020, 01:39:41 pm
content: Quote from: Wytnucls on August 23, 2020, 09:31:04 amI sold mine 121GW at eBay bevor some weeks......And yes, other companies also had some problems with their instruments. But they fixed the (most) issues or even scrapped complete production-batches therefore. We are discussing since years about the 121GW issues mostly without any progress.And it shows: To have some really good ideas for a product is one thing. (The 121GW has a lot of good features without any doubt) To bring this to flawless work is another thing and that is much more tricky.

author: Wytnucls
author_rank: Super Contributor
timestamp: August 23, 2020, 02:16:33 pm
content: Is that the only one 'aus Deutschland', that was sold for 95 Euros in May?Should have got a refund from Dave instead, if that's the one.Gossen makes some great meters, but they are rather expensive and often prone to lockup in a strong magnetic field. I don't think that has been fixed yet.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 23, 2020, 03:28:49 pm
content: Quote from: Wytnucls on August 23, 2020, 02:16:33 pmI've only evaluated that Ultra which had a pretty obvious design flaw with the lack of shielding. I would have thought that the latching relays was unique to this product but from your post is sounds like they have been having problems with other models. Odd as Dave has reviewed them and it was never mentioned. My Ultra never locked up. Gossen never did respond to my question about the reason for the Ultra's name change and if they had actually improved the product.

author: chronos42
author_rank: Regular Contributor
timestamp: August 23, 2020, 03:35:14 pm
content: Quote from: Wytnucls on August 23, 2020, 02:16:33 pmYep, that was this one aus Deutschland. I had this meter some years, it was from an early batch (still with the famous 4007 Diodes), so no way for a refund. It was very seldom used, I only miss the 15V diode testfunktion, but a peak atlas ZEN50 tester now does this job.And yes, I am aware oft the "strong magnetig field" problem, that some Gossen meters have, first found by Joe. (Including my Metrahit Energy) But the Gossen meters are not the only one with the relais issue. My Agilent 1252B also has a relais, that can be forced to switch with an external magnet. And I am sure that there are some more meters with this issue. Except you are working near cryostatic magnets or high power transformers, this should not be a real world problem.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 23, 2020, 04:00:07 pm
content: Quote from: chronos42 on August 23, 2020, 03:35:14 pmWhile talking with owners of Chauvin Arnoux products, it seems they also use latching relays in some of their products. With my Gossen Ultra, even a magnetic hanger was enough to cause it to change states. The 121 was very sensitive to alternating magnetic fields in the 60Hz range. Unlike the Gossen that could latch into a state where it may not display proper voltage levels, the 121 would just wander.

author: chronos42
author_rank: Regular Contributor
timestamp: August 23, 2020, 04:21:01 pm
content: As I said, the Agilent 1252b also uses one latching relay in the AC/DC path. A lot of older Philips/Fluke scopemeters also in the attenuater circuit.

author: MiroS
author_rank: Regular Contributor
timestamp: August 23, 2020, 07:02:56 pm
content: Looking arround I found some mutimeters, they are not known to me at all.They cover wide range of products, probably made in India and rebranded, most interesting for me is NP15B:https://www.lumel.com.pl/en/catalogue/categories/multimetryI do not know anyone who had experience with them.For me a bit interestining, they suppose to have local reapir service and development lab.At the and this is EU , so potential customers are protected by EU law. It looks like this comany is owned by Rishabh Instruments .https://rishabh.co.in/products/13/digital-multimeterSome opticaly are similar to Metrahit.

author: MiroS
author_rank: Regular Contributor
timestamp: August 23, 2020, 07:26:15 pm
content: Quote from: 2N3055 on August 23, 2020, 11:10:27 amI own three of Chauvin-Arnoux, thay are old, but still are OK.Higher end multimeters are looking like tricorders from Star Treck, but unfortunately they are not offering similar functionality

author: tautech
author_rank: Super Contributor
timestamp: August 23, 2020, 09:13:57 pm
content: Quote from: rsjsouza on August 23, 2020, 12:26:17 pmYes however with events this year and better public understanding (thanks Dave) of Siglent's capture memory management strategy Nico's concerns from way back then are diminished as we all better understand each others POV. Such are the difficulties of getting points properly understood when not in our native language.BTW, not seen Nico around lately, hope he's alright and not got this terrible Covid thing.Oh, and about the excluded caps in early releases of SDS1202X-E, it wasn't SDS1104X-E !I made my thoughts clear at the time how Siglent needed to fix that but the US manager at the time couldn't/wouldn't enact the processes to make it happen so to this day we still have embittered ex customers.Anyways, enough OT, over and out.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 24, 2020, 07:12:29 am
content: The specs for the UEI DM525 are already available. From this it looks like the new meter uses the digital RMS part instead of the extra AD8436 - a totally sensible decision: the main downsides I see is lower bandwidth and it looks like slightly higher power consumption.The case design really looks like a rip off - take it as a complement.

author: CDaniel
author_rank: Frequent Contributor
timestamp: August 24, 2020, 08:26:27 am
content: That meter is for electricians working primary on mains stuff , so AC bandwitdh is low , maybe 1KHz . It is compared to Fluke 179

author: Wytnucls
author_rank: Super Contributor
timestamp: August 24, 2020, 08:30:22 am
content: Lower bandwidth?20kHz is rather high for a 6000 count multimeter (2%+20). (Highest of all 6000 count multimeters actually)It must have an external true RMS to DC converter.5kHz on amps.

author: EEVblog
author_rank: Unknown
timestamp: August 24, 2020, 08:50:18 am
content: Quote from: Kleinstein on August 24, 2020, 07:12:29 amNope, uses the AD8436.Schematic is very similar to the 121GW, it's based mostly on that design.

author: joeqsmith
author_rank: Super Contributor
timestamp: August 24, 2020, 04:39:26 pm
content: Just to be clear when I made the comment:Quote, I was referring to Gossen products.Quote from: chronos42 on August 23, 2020, 04:21:01 pmMy old Fluke 97 scopemeters use them. Out of interest, I used that same magnet I used to demonstrate the problem with the Gossen Ultra to see if the Fluke was sensitive to it. I tried moving the magnet all about the case and it had no effect. So I brought out the tape eraser and held it right next to the case fully expecting the relays to chatter but nothing.Mine is using Takamisawa RAL3W-K. These are physically much larger than the relays used in the Gossen. They also have some metal shielding around them which may help.https://www.fujitsu.com/downloads/MICRO/fcai/relays/ra.pdf