Aneng SZ20 25,000 count, 1uV, 10nA, 20A - Page 1
Forum section: electronics / testgear

author: DX1
author_rank: Contributor
timestamp: March 25, 2023, 06:44:13 pm
content: New Aneng meter SZ20 Just over £50 on ebay in the UK. Or £33 on Aliexpress.Origin: Mainland ChinaModel Number: Digital MultimeterDisplay Type: Digital displayPower supply: 2xAA battery (not included)Size: about 18x9x5cm/7.09x3.54x1.97inColor:Red,Black(optional)Material: ABS/siliconePlease note that the battery is not included in the shipment.standard:Function Range Resolution AccuracyDC voltage 0mV-1000V 0.001mV to 0.1V ± (0.2%+10)AC voltage 0mV-750V 0.001mV to 0.1V ± (0.3%+3)DC current 0uA-20A 0.01uA-0.001A ± (0.5%+3)AC current 0uA-20A 0.01uA-0.001A ± (0.8%+3)Duty ratio 1%~99% 0.1% ± (0.1%+2)Resistance 0Ω - 250MΩ 0.01Ω - 0.1MΩ ± (5%+5)Capacitance 0nF-99.99mF 0.001nF to 0.01mF ± (5%+20)Frequency 0Hz to 10MHz 0.01Hz-0.001MHz ± (0.1%+2)Temperature℃ - 20~1000°C 1 ℃ ± (3%+5)Temperature°F - 4~1832°F 1°F ± (3%+5)Flashlight DiodeData retention period Turn on and off beepScreen backlight NCV detectionLow battery reminder Silicone sheathAutomatic shutdown Back supportMaximum count 25000Just to draw attention to a new 1uV multimeter.1uV DC resolution is very valuable for low burden current checking with a shunt resistor and also finding shorts on a ground plane.The extra resolution is helpful, though not matched by the claimed accuracy.If only Aneng could actually design for proper safety like Fluke. I cannot cost that much more surely?Obvious comparison is Aneng AN8008 10,000 count 1uV meter for about £20.

author: Fungus
author_rank: Super Contributor
timestamp: March 25, 2023, 07:01:15 pm
content: I think I'll get one for the wrought iron screen and thunder monitoring feature.https://www.aliexpress.com/i/1005005201649970.html

author: Fungus
author_rank: Super Contributor
timestamp: March 25, 2023, 07:04:48 pm
content: Quote from: DX1 on March 25, 2023, 06:44:13 pmMuch cheaper on Aliexpress (33 Euros).Quote from: DX1 on March 25, 2023, 06:44:13 pmIt has fire proof fuses.

author: floobydust
author_rank: Super Contributor
timestamp: March 25, 2023, 07:19:27 pm
content: I think it's got 5x20mm, haven't seen any PC board pics. 25,000 count is nice hopefully real counts and not some clever filtering to get more from a lower resolution ADC.We still don't really know who the chip supplier is. Dreamtech just does application specific F/W I believe for Hycon?

author: Kleinstein
author_rank: Super Contributor
timestamp: March 25, 2023, 07:28:17 pm
content: Getting µV resolution is no more that expensive and the chips set seems to support this.Better protection can actually add costs - this starts with the fuses, that in QTY 1 may cost $5-10 and the usual meter needs 2 of these.The other point is additional space needed in the case and also for the switch. It can be tricky to combine good protection for a CAT 3 rating with some functions. The protection part may add some noise / drift. High sensitivity and good protection combined is an additional challange.It would still be nice to get a meter with good protection at a competative price, but that would be more like a different meter.For many meters it would help a lot to have an honest CAT rating - which costs about nothing. Another point would be to add 1 spare fuse for the low current range - so one could directly see what type.The moden chip sets tend to use sigma delta ADCs. So it is a kind of clever filtering to get the resolution. If done right there is nothing wrong with this. 25000 counts is not really challenging to get the linearity right.

author: floobydust
author_rank: Super Contributor
timestamp: March 25, 2023, 07:48:46 pm
content: Is this ADC ENOB true to the rating? The AN8008 has a deadband at +/-4uV to mask noise and flicker. That was a surprise to see it reading zero and then jump up. So they use clever processing that nobody really checks out. The averaging is also clever as well, if you test it. Capacitors cost a lot of money, for quiet VDD lol."Real" CAT ratings i.e. 61010 certification costs thousands of dollars and these meters would not pass anyway. I'd rather have a "1,000V Max." rating (and tested) so you know it can at least work there in Cat. III see puny little green NTC so I am not optimistic.

author: mwb1100
author_rank: Frequent Contributor
timestamp: March 25, 2023, 10:34:14 pm
content: Putting technicals aside, there seems to be a slew of meters coming out with that same physical design.I wish they wouldn't.

author: Fungus
author_rank: Super Contributor
timestamp: March 26, 2023, 03:12:11 am
content: Quote from: mwb1100 on March 25, 2023, 10:34:14 pmIt's ugly as hell, IMHO.Quote from: floobydust on March 25, 2023, 07:19:27 pmIt might be 6x30. Aneng sells that size in their store:https://aneng.aliexpress.com/store/group/ANENG-Accessories-and-others/919484_516409721.htmlWeird: I went there with a different browser and they're selling their test leads with 99% discount. There's some sets for 1 cent with free shipping, and a fairly decent set for 18 cents with free shipping. I thought I'd snap up a dozen but then I went in with my real account and they cost $4.

author: floobydust
author_rank: Super Contributor
timestamp: March 26, 2023, 03:52:40 am
content: Yeah Aliexpress shows pricing with the "Welcome Deal" new user bonus" as a bait and switch lol. Or the item's price is all shipping fee. It's all so tiring.I got some of those cheap multimeter test leads... Overall the probes are way too big (fat, long) to handle well especially with the needle tip. YUCK. Had to laugh one set won't fit in the banana jack, the plastic shroud a little too large diameter. That's why it was $2.I like the original AN8008 smaller probes but I can't find them. I don't need a mile of wire either.Tried the "20A silicone" um er no, it has el skinny wire copper is like gold. The chrome plated tips are shit, they don't make a good connection to anything.Just like these multimeters, only one true manufacturer and what stores sell, everything is pretty much the same. They all look the same.It seems probes have to be gorilla big and there are maybe 3 different injection moulds in the entire country. I wish the People could refine things.

author: DX1
author_rank: Contributor
timestamp: March 26, 2023, 08:14:07 am
content: BS1362 fuses (6.3mmx 25mm) are cheap and readily available in the UK. They open safely with a dead short on 230V mains.Rated at breaking 264V AC at 6kA.So much better than most meters and probably all most people would ever need.Quote from: floobydust on March 25, 2023, 07:48:46 pm

author: Fungus
author_rank: Super Contributor
timestamp: March 26, 2023, 10:32:08 am
content: Quote from: DX1 on March 26, 2023, 08:14:07 amYep, I don't know why they aren't used in everything.

author: DC1MC
author_rank: Super Contributor
timestamp: March 26, 2023, 11:36:48 am
content: I've bought one so you don't have towith alll accessories from the ANENG official store:https://www.aliexpress.com/item/1005005201649970.htmlSummaryTotal item costs € 49,00Saved -€ 7,57Total shipping FreeTotal€ 41,43 VAT includedIs anyone around Mannheim/DE with some calibrator gear willing to spend some time with me testing/characterizing the beast ?Eventually if you're to far away I can ship it to you, PM me if interested.Cheers,DC1MCP.S. Yes, I know, but there was really nothing available on the EBAY/KA to get as a comfortfoodTE after emerging from a very messy Covid.

author: Cliff Matthews
author_rank: Unknown
timestamp: April 01, 2023, 09:39:11 pm
content: Some board pic's on video?It's the one on the right with MOV protectionhttps://youtu.be/W9UhA54JboA?t=979

author: floobydust
author_rank: Super Contributor
timestamp: April 01, 2023, 10:20:46 pm
content: Another cheeseball review. "all the MOV's are on the voltage side" uh no the V jack is on the other side! Just because you see MOV's or PTC's etc doesn't mean the PCB/rotary switch spacings are done correctly. This is why you get this stuff tested instead of making Cat. III claims. Anyone take one apart and follow the V input jack traces, I bet they are terrible and it would autodestruct and arc to something.The LCD update rate is slow, I would say they are using decimation to get the 25,000 counts out of the DM0660.NCV missing the probe piece LOL. The last cheap tester I got with no sensor metal flag detected nothing very well, that was scary. So I added it and got accurate bleeps on hot wires.

author: Cliff Matthews
author_rank: Unknown
timestamp: April 01, 2023, 10:55:59 pm
content: Yeah I knowbut it's so new it's the only one I could find.

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2023, 11:06:03 am
content: As promised, I've sacrificed my self for you and got one, be grateful, and now it arrived !!!So, some teasing photos, if there is interest (expressed in thanks and messeges) I'll post detailed pictures of the insides. If not, not.Meanwhile the device works nice, the display is pretty good AFTER one peels off the protective foil, the backlight of the display is indeed connected to the lantern LED, and the most important part:THEEEE FUUUUUSEEEES !!!!There are two 20mm fuses, one 0.6A/250V and one 20A/250V with ceramic bodies, so your flukes are in no danger to be replaced anytime if you measure turbines and industrial generators.But it does come with a special sticker on top of the Amps socket that you'll see in the pictures.The reference is an ICL8069, the brains a DTM0660L, an, EEPROM P24008C and a LCD controller ET6621S.The NCV piece of metal is not soldered, but also not necessary, there is a long PCB trace parallel with the end of case that works very well, I will probably put a piece of copper foil to increase it even more.The probes (two sets) and accessories are OK.Cheers,DC1MC

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2023, 05:23:37 pm
content: Well then, if no one requested hi-res picture, you'll have to survive with average res pictures, so here they are, I won't open it again, I've almost lost the kliky-klaky steel balls.BTW, there is some kind of grease on top of the switch contacts, should I clean it or should I leave it ?Cheers,DC1MC

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2023, 05:42:15 pm
content: Seems to have more-than-the-average-Aneng input protection. And some MELFs!Quote from: DC1MC on April 06, 2023, 05:23:37 pmLeave it. It's factory installed to make the contacts last longer.

author: Cliff Matthews
author_rank: Unknown
timestamp: April 06, 2023, 05:43:13 pm
content: I vote at this price it's a good candidate for MELF robustness testing

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2023, 05:52:33 pm
content: Quote from: DC1MC on April 06, 2023, 11:06:03 amI was going to complain about the length of the fuses but then I saw the spacing on the PCB underneath them:What is that, 2mm?

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2023, 06:01:18 pm
content: Using highly advanced electronistic Schibler I can confirm that one of the gaps is 3mm and the other one (20A) is 4mm. I've also checked that a cut could be dremeled in both without hitting anything, if I do it can I measure voltage on current setting of 500KW hydroplant generators safely ?

author: Kleinstein
author_rank: Super Contributor
timestamp: April 06, 2023, 06:08:59 pm
content: Even with more distance below the fuse the safety would not improve a lot. Instead of a cut, it may be easier to add some epoxy glue on top of the copper. A cut could effect the mechanical stability.

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2023, 06:14:17 pm
content: Quote from: Kleinstein on April 06, 2023, 06:08:59 pmAraldit it is, the transparent version, I'll call it the "Plasma Breaker Edition"Other wisdom before putting it back and asking for some kind soul to characterize it for me ?Cheers,DC1MC

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2023, 06:17:23 pm
content: Quote from: DC1MC on April 06, 2023, 06:01:18 pmI think the 20A is smaller, there's an even narrower part above the fuse (see new image).You could certainly Dremel off that pointy bit if you're going into a high energy area.

author: DC1MC
author_rank: Super Contributor
timestamp: April 06, 2023, 06:24:29 pm
content: Quote from: Fungus on April 06, 2023, 06:17:23 pmQuestion is, WHY do they do this, is obvious that is a very simple issue to fix, you don't need special technologies or design tools to make sure that the spacing constraints are met, also the pointy bit, that I will with fire and diamond tip has no purpose, not even some vias, and all the other crap could have been ultra-easily avoided.Could it be to keep the higher end models competitive, or is something to sabotage the western devils, or even, for 99,99(9)% of use cases these precautions are not needed ?Wondering,DC1Mc

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2023, 07:57:24 pm
content: Quote from: DC1MC on April 06, 2023, 06:24:29 pmThere's no rational explanation except mismanagement. The person who did the PCB obviously doesn't know that stuff.The meterworksso that's it.

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2023, 08:03:38 pm
content: Anyway:Now you have one can you tell us what you think of the wrought iron screen and thunder monitoring feature?

author: Kleinstein
author_rank: Super Contributor
timestamp: April 06, 2023, 08:22:00 pm
content: There are other areas with stupid small spacing, e.g. with the 2nd PTC that is rather close to the main chip set, but electrically more or less connected to the input, at least in the Ohm mode.The spacing at the switch is a but more tricky. So this may need more space there. The switch part is quite often a weak point.I can totally understand the rant: I can accept using cheaper fuses (though not the stupid 5x16 size), especially if the lable would be accordingly.A sloppy layout does not reduce the BOM costs very much. No real excuse for this.

author: Fungus
author_rank: Super Contributor
timestamp: April 06, 2023, 08:34:01 pm
content: Quote from: Kleinstein on April 06, 2023, 08:22:00 pmIt doesn't reduce it at all.If they want to reduce the BOM they could get rid of a few of those drill-holes-to-nowhere in the oversized pads under the fuses. Drilling costs money.

author: floobydust
author_rank: Super Contributor
timestamp: April 06, 2023, 09:48:31 pm
content: Thanks for the pics, my concern was with the HV input jack trace doing a long drive across the board.Informal armchair looksee, the PCB layout is an ongoing weakness. Either the creepage/clearance are not consistent, or lots of dead copper, ground-pour over regions that should or shouldn't have any, and scarce via's etc. It's a layout limitation due to inexperience. Wisdom is gained through testing.5x20mm specialty fuses can be rated almost 500VAC so the fuse PCB gap is meh, it could only arc after fuse clearing.The HV divider MELF's are way up the board and a few traces too close. MOV traces too skinny. Three via hole sizes? I could go on.For the (IEC 61010) 600V Cat. IV 1,000V Cat. III label it bears, well that is an 8kV impulse test and no that won't be achievable. In practice what you do is take a PCB and give it even half that and see where it arcs and crackles in a dark closet. I marked up the top side pic with a few regions I didn't like, the rotary switch is strange having solder-mask on the track, which wears off... for a design review V1.0 needs polish.It might do fine with household use to ?V but... always test instead of speculate. It takes just one spacings error to fail. Or a component - here there is no 1kΩ surge resistor so a tiny PTC rated for harmonious 1,000V usually just blows up without that anyway. I just want to know if it's OK for mains use- to what voltage and with no certificates/approvals hard to trust.It's an improvement over previous models. 3-LED backlight. It has an LED at the 20A jack? Pt1.7 could have serial dataI'm wrong about the missing NCV electrode, they are using a long trace from side to side for that.Hopefully the LCD contrast and update rate is good. $50 for 25,000 counts I wonder how it does with fine measurements. Would scope power and upsize caps as required.

author: DC1MC
author_rank: Super Contributor
timestamp: April 07, 2023, 01:00:46 am
content: Sometimes I have these crazy post-Covid dreams, let me share one of of them:As far as I can see, the main weakness of this devices is not the parts, they seem to be half decent, not even the case, but the layout of the PCB that for one reason or the other, seem to not improve over time.So the idea is: keep the case and redesign the PCB properly, and then transfer the main parts from one PCB to the other, where it makes sense (MCU, LCD & controller, some resistor, etc) and have the community designed device.Of course is not that there is a lack of highly performant and expensive multimeters all over the place, but hear me out: if the PCB is highly performant and the result is really good, we make it public and it will be copied only with small adaptations that I hope will not destroy its purpose and suddenly will will have an abundance of cheap but safe and performant multimeters.Myself I can do measurements, transfer parts and do testing, hey I may even sponsor the PCB ordering and send them to the interested, if it works with cars tuning and other things, why not with the multimeters, then we send the result to Dave and count "meeehs" compared wit the original.What do you say about this crazy Easter idea ?Cheers,DC1MC

author: Kleinstein
author_rank: Super Contributor
timestamp: April 07, 2023, 07:44:58 am
content: The parts are also not that great, at least not for the claimed 1000 V cat 3 rating. As far as I can see there is no series protection (e.g. fusible resistor) in case the first set of MOVs fails. There are MOVs that include a thermal link, but I somewhat doubt these as such types. For a 1000 V CAT 3 rating the 2 MELF resistors for the voltage path also look a bit small, though better than many cheap meters.The tricky part can be the spacing at the switch, though it does not look that bad. It looks like the the wiper next to the critical switch part (outer 2 traces towards the terminals) is not populated. So the solder mask covered part in the switch just looks strange - though a little close to the input voltage. The 2 small uncovered spots may be for testing - though still odd.For the low voltages it may be interesting how good the resolution really is - not just at 0 V (in case there is a dead band). Having a dead band and thus crippling the low voltage range would be a show stopper in investing more time in the PCB.For the µA range, I don't see a big issue. The current is not super low and it is just a simple shunt. No special problems expected there.

author: Fungus
author_rank: Super Contributor
timestamp: April 07, 2023, 07:51:37 am
content: Quote from: floobydust on April 06, 2023, 09:48:31 pmBut basic accuracy is only (0.2%+10)Aneng AN870 is 20,000 counts and (0.05%+3) for less money.https://www.aliexpress.com/item/33052395019.html

author: indman
author_rank: Super Contributor
timestamp: April 07, 2023, 02:11:01 pm
content: Quote from: Fungus on April 07, 2023, 07:51:37 amAnd here is a screenshot with characteristics for a similar multimeter, only with a different marking!NEWRUIKE XCRK61E. Specified 0.05%+3 basic accuracy. Which characteristics do you suggest to trust more? Or does it have a different filling inside?

author: Fungus
author_rank: Super Contributor
timestamp: April 07, 2023, 02:55:36 pm
content: Quote from: indman on April 07, 2023, 02:11:01 pmLooks like it came out of the same factory to me.Aneng are rebadgers, I don't know if they make any meters themselves. They're sold a lot ofZotekmeters in the past. Now it looks like they're using somebody else.FWIW many Aneng meters have "ZT" part numbers on the PCB, eg. the AN870 shown onthis page:I can't see any markings on the SZ20 PCB pics posted by DC1MC though.(maybe they're under the LCD...)

author: mwb1100
author_rank: Frequent Contributor
timestamp: April 07, 2023, 03:33:00 pm
content: Quote from: Fungus on April 07, 2023, 02:55:36 pmThe Aneng SZ20 is aZotek (aka Zoyi) ZT-225The Aneng PCB mentions "225" without the "ZT". Maybe a weak attempt to obscure the link? Probably nothing so deliberate - just what the board layout guy typed in.

author: indman
author_rank: Super Contributor
timestamp: April 07, 2023, 03:41:51 pm
content: Don't you understand yet that all cheap counters are made by Chinese friends on their knees in a dim basement, and then different labels are stuck on the same case - ZOTEK, ANENG, NEWRUIKE and others. And the characteristics are also what you want, they will draw them in the table!

author: DC1MC
author_rank: Super Contributor
timestamp: April 07, 2023, 04:13:57 pm
content: Quote from: indman on April 07, 2023, 03:41:51 pmWhat about the highly expensive counters, are they made by Americanians in highly advanced SF laboratories?

author: indman
author_rank: Super Contributor
timestamp: April 07, 2023, 04:23:38 pm
content: Quote from: DC1MC on April 07, 2023, 04:13:57 pmNo, I think they are also made in China, only in contrast to the conditions of the basement, Chinese friends wash their hands there more often.

author: Fungus
author_rank: Super Contributor
timestamp: April 07, 2023, 05:56:09 pm
content: Quote from: mwb1100 on April 07, 2023, 03:33:00 pmHah! They fooled me by not putting it on theirweb site.I wonder what the true specs are.Quote from: indman on April 07, 2023, 03:41:51 pmZotek is the manufacturer."Zoyi" is the official Zotek brand, everyone else is a rebadger.

author: indman
author_rank: Super Contributor
timestamp: April 07, 2023, 06:01:56 pm
content: Quote from: Fungus on April 07, 2023, 05:56:09 pmZotek is the manufacturer advanced SF laboratories in China?! You made my house slippers laugh

author: Fungus
author_rank: Super Contributor
timestamp: April 07, 2023, 06:13:17 pm
content: What's the diode test voltage on this meter?(and why do they never publish that number?)If the 0.05%spec is the correct one then this could be a meter worth owning. Maybe the ZT219 (AN870) has a successor...I like that it has a separate dial position for each function.

author: tooki
author_rank: Super Contributor
timestamp: April 07, 2023, 09:39:25 pm
content: Quote from: Fungus on March 26, 2023, 10:32:08 amWell, some users (electricians, especially industrial electricians, though almost none of us electronics people) need safety ratings beyond CAT II, which is where the BS1362 fuses operate.I’d actually love to see BS1362 fuses used in cheap multimeters, combined with an honest CAT I or II rating, instead of little glass fuses or none at all.

author: Fungus
author_rank: Super Contributor
timestamp: April 07, 2023, 10:31:53 pm
content: Quote from: tooki on April 07, 2023, 09:39:25 pmDon't expect it from China. The precedent has been set, the horse has bolted, the ship has sailed.

author: DX1
author_rank: Contributor
timestamp: April 08, 2023, 05:28:45 pm
content: Could someone please do a test of the uV range? For example measuring current shunts or finding shorts on ground planes. Looking for noise, monotonic increase of measured uV with increase of input, thermal effects and accuracy. A power supply with voltage divider (using good resistors) is probably a good enough source of microvolts, though would be useful to check against a proper meter.

author: DX1
author_rank: Contributor
timestamp: April 08, 2023, 06:03:07 pm
content: I am amazed nobody has access to surge testing equipment. It would be really helpful to do some actual tests on these cheap meters. This meter seems better than most, but the PCB does not seem to be laid out that well and the fuses and MOVs could be bigger. MOVs have a limited surge life and can only take a few of the rated surges, after which they can be prone to thermal runaway, which could be a real risk if you are trying to fix a fault. You can now get MOVs with an integrated thermal fuse.What we need is honest ratings, preferably with a test report from a credible test house. You are not going to sell these meters to someone who actually needs 600V Cat IV. Even if it passes the tests I would still buy a reputable make for this.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 08, 2023, 06:27:37 pm
content: Quote from: DX1 on April 08, 2023, 06:03:07 pmThere is no real need to destroy a meter that is not yet bad. It is obvious that the protection is not that good to be used for high voltages and even if the meter survives the test the MOVs may show leakage.The real interesting test would be the performance with low voltages. That is what this meter and few other new ones offer than many other DMMs don't.

author: Fungus
author_rank: Super Contributor
timestamp: April 08, 2023, 06:29:04 pm
content: Joe's done some Anengs:

author: floobydust
author_rank: Super Contributor
timestamp: April 08, 2023, 06:54:23 pm
content: Realistically, true Cat. III 1,000V/600V IV ratings to 8kV impulse require: around 8mm PC board spacings, 10x38mm fuses, tough MOV's, bigger PTC, surge resistor etc. ...which make a multimeter huge and expensive.It's not realistic for these low cost products, you cannot have your cake here. People here know the label, claim is a deception. This is all about price and we'll compromise anything for getting it cheap.Real surge testing equipment is very expensive and destructive, you'd need a pallet of these multimeters to test. Nobody here would do it for three reasons - one, it's gonna fail. Two, you can't "test in" safety, you have to design it in first. Think about it, will the plane go to 500km/h? Blows up at 200km/h, now what? Rate the plane to 199km/h? but a windy day...Three, you don't want to endorse a test-pass for the legal repercussions and the politics of safety approvals.If this meter can withstand 1,000V safely (and that is with no mains transients to 8kV claimed or expected), like multimeters of old, then that is good enough as Cat. II use.I've worked in Cat. III, IV and would never use anything without formal 61010 testing and certifications there. That's why I still have my hands.It's interesting the spiral around fake 61010 claims and an unknown truth about the usage safe limits.The user manual and prerequisite front pull-off sticker on the amps jack kind of tell you not to use this up there yet the jack Cat. xx label is commonplace malarkey.

author: bastl_r
author_rank: Regular Contributor
timestamp: April 08, 2023, 07:23:44 pm
content: Quote from: DX1 on April 08, 2023, 06:03:07 pmHiDo you mean surgetests like this?by the way: The Aneng 870 is a good cheap Multimeter. I paid for my item 25$ on a black friday sale.

author: DC1MC
author_rank: Super Contributor
timestamp: April 08, 2023, 07:50:57 pm
content: Quote from: Fungus on April 07, 2023, 06:13:17 pmTo answer this question:- Diode mode voltage: 3.3234V- Resistance mode voltage 0.502VEquipment used: Fluke 8060ATest point P.7 not scoped, if there is data there then I have to fall into a rabbit hole and use the "flashlight" LED to send it out, then make an adapter to receive it and so on, too much scary workand what if it works ?!?!Cheers,DC1MC

author: floobydust
author_rank: Super Contributor
timestamp: April 08, 2023, 08:02:34 pm
content: You are no fun, scope "Pt. 1.7" so we can see if it's possible to get serial data out of this...

author: Kleinstein
author_rank: Super Contributor
timestamp: April 08, 2023, 09:03:19 pm
content: Getting data logging could help judging on the noise. Manual reading is a bit slow and maybe subjective if the update rate is not very slow.

author: DC1MC
author_rank: Super Contributor
timestamp: April 08, 2023, 09:13:07 pm
content: Quote from: Kleinstein on April 08, 2023, 09:03:19 pmIf Dr. Kleinstein says it could be useful, I'll do it, zum Befehl, is actually due to the (small)garden work of today that I'm early in the bed, I still try to fully recover from the C19, I'll scope it tomorrow and if it spits data, I will try to decode it. Actually I will scope all test points.If anyone knows any "tricks" on similar but smarter instruments to enable somehow data logging, please say, I'll try (almost) anything tomorrow.Cheers,DC1MC

author: DC1MC
author_rank: Super Contributor
timestamp: April 08, 2023, 09:29:24 pm
content: Every frigging time, ones try to do something a quick google search shows that someone else did it already seven years agoPlease have a look on this google cache of a long gone page:http://webcache.googleusercontent.com/search?q=cache:fg0T_DOmrEYJ:www.kerrywong.com/2016/03/19/hacking-dtm0660l-based-multimeters/&cd=1&hl=en&ct=clnk&gl=deI'll save a pdf of it and eventually attach it here, it has all the info needed to enable logging.Cheers,DC1MCEDIT: Not only this, but an EEVBLOG post as well:https://www.eevblog.com/forum/testgear/hacking-dtm0660l-based-multimeters/EDIT2: MCU translated datasheet added.EDIT3: Kerry Wang's excellent tutorial added as PDF (his website is not working anymore)

author: floobydust
author_rank: Super Contributor
timestamp: April 08, 2023, 11:02:11 pm
content: No- DTM0660L has many different faces. 4,000 or 6,000 or 9,999 or 25,000 count along with different functions - it's not guarateed to be the same IC. My belief is Dreamtech does the application firmware for the OTP multimeter MCU+ASIC which seems to be made by Hycon. We don't know all of the mystery here. Try the scope probeThe serial TX pin is not bonded on the COB versions.

author: tooki
author_rank: Super Contributor
timestamp: April 08, 2023, 11:20:54 pm
content: Quote from: Fungus on April 07, 2023, 10:31:53 pmI said that I’d love to see it. I didn’t say I expect it to happen!

author: floobydust
author_rank: Super Contributor
timestamp: April 09, 2023, 01:27:26 am
content: ICKBS1362 aren't used in North America. We have 5x20mm and then 1/4"x 1-1/4" (6.3*32mm). Going beyond 250V brings us to specialty fuses.Specialty 1/4"x 1-1/4"Littelfuse508 are good to 1A 1,000V 10kA interrupt. Seems high 3.572Ω resistance for 0.5A part. For say 15A, 506 series is good to 600V 10kA.

author: DC1MC
author_rank: Super Contributor
timestamp: April 09, 2023, 07:23:32 am
content: First preliminary tests with the data logging issue:- Holding long the REL button does not bring anything on display.- At startup there is a moment where all the LCD annunciators are on, there is nothing that I can see that suggest any kind of PC link or data logging.- Looking closer on the PCB around EEPROM there was some rework stuff done, a resistor (WP ?!?) seems to have been removed.This post will be edited after scoping the test points and/or if I can read the EEPROM.EDIT1: these are the test points scoping results:Pt1.7 - Beautiful buzzer signal, 'cause this is so much needPt1.0 - Some signal ONLY when pressing once REL, it looks like some very shot spikes with 30ms spacing, RIGOL's anemic RS-232 decoder is not avle to do anything with it.Pt1.1 - Solid one.The bloody buzzer produces a 200mV signal mirroring on the power supply, probavly the consumtion is enormous, but the electricians want loud buzzers.Now, I can unsolder and read the EEPROM as well as trying to do the modifications in the previous PDF, please tell me seriously if it is worh doing.Cheers,DC1MC

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2023, 03:47:48 pm
content: Quote from: floobydust on April 09, 2023, 01:27:26 amI think you missed the point: the reason that BS1362 fuses would be ideal isn’t because of their size, but because BS1362 fuses are manufactured in gargantuan volume (thanks to being used in every single British AC power plug), making them incredibly cheap, likely the cheapest ceramic fuses that in any way resemble a HRC fuse. Specialty fuses from Littelfuse won’t be cheap, so they wouldn’t get used by cheap DMM makers.

author: DX1
author_rank: Contributor
timestamp: April 09, 2023, 05:57:42 pm
content: Instead of Cat II, cat III etc we should rate most cheap meters as protected for connection directly to consumer 230V. Which covers 99% of hobby users.And a fail safe rating of, for example, 8kV 2 ohm surge and 2000V DC.With fail safe suitable for dead short across consumer 230V, for example a BS1362 fuse.The manufacture would be required to provide a survive rating.Tests for fail safely are used, for example, on 230V wall sockets.Fail safe basically means no expelled parts and no fire.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2023, 06:04:04 pm
content: Isn’t that exactly the purpose of the CAT ratings? The only part that’s non-obvious about them is knowing which category means what. That could be easily solved with a little diagram in the manual.

author: DC1MC
author_rank: Super Contributor
timestamp: April 09, 2023, 06:33:34 pm
content: Out of nothing better to do I've desoldered the 24C08 and read it, maybe the more enterprising people will be able to see if there are special settings for 25k count, now that the bloody Amtech flux spread allover I have to ultrasound clean the board and this being said I've also removed the LCD just because it seems that the UART TX is going somewhere in an unknown area, I hope they didn't repurpose it for some strange stuff or on the 25K chip is somewhere else as in the data sheet.EEPROM dump attached, average res pictures of what's under LCD will follow.Cheers,DC1MCNOTE: Remove the .zip extension from name, this is a pure bin file, needed for forum file types restriction.

author: floobydust
author_rank: Super Contributor
timestamp: April 09, 2023, 06:47:51 pm
content: Availability - BS1362 1"x1/4" fuses are nowhere to be found in North America, and being rated to only 250VAC they have the same ability as 5x20mmI don't quite get their allure.To keep multimeters small yet have a high voltage say 1,000V rating, in the utility industry the fuse is located in the probe where there is lots of room.Many multimeters have bad PC board designs and arc "somewhere" else. They are untested. This is the main problem.There is serial data in order to do factory calibration, and without the beep beeeeep beep beep. So PT1.7 should have something on it? Calibration mode is a jumper to GND on PT1.3 or about that resistor you say is removed. Or maybe it's a special button press on power up.

author: DC1MC
author_rank: Super Contributor
timestamp: April 09, 2023, 07:32:44 pm
content: Well, not so cool news, the EEPROM content doesn't make any sense to me, at least compared with the known 6K/9K datasheets, it seems that there's some difference in the organization, to make things worse, the alleged TxData pin (the one that goes under U2(EEPROM) is now part of the buttons matrixso if you don't suggest any directions to proceed, I'm stuck.HALP!!!DC1MC

author: Gyro
author_rank: Super Contributor
timestamp: April 09, 2023, 07:52:43 pm
content: Quote from: floobydust on April 09, 2023, 06:47:51 pmThe 6kA interrupt rating, something you can't get in 5x20mm.

author: tooki
author_rank: Super Contributor
timestamp: April 09, 2023, 08:10:20 pm
content: Quote from: floobydust on April 09, 2023, 06:47:51 pmI know that. But they’d be inexpensive to procure. It’s not like you can get multimeter fuses at your local hardware store, either.Quote from: floobydust on April 09, 2023, 06:47:51 pmBecause voltage isn’t the only criterion!! A standard 5x20mm fast-blow glass fuse has a current breaking capacity of just 35-100A (using Schurter as an example). That is nowhere near enough to be working on mains where thousands of amps are often available. 5x20mm ceramic fuses are already a lot better, 500-1500A. But a BS1362 fuse is rated to 6000A breaking capacity, closer to the 10kA of a real multimeter fuse than not.Using them would be a really inexpensive way to increase safety a lot. Not to real CAT III or IV, but to a whole lot better than a tiny glass fuse.Simply due to economies of scale, BS1362 fuses are among the cheapest sand-filled ceramic fuses in existence.Another cheap option would be sand-filled ceramic 1/4” x 1-1/4” fuses, which have even better breaking current ratings than BS1362, and cost only slightly more.

author: floobydust
author_rank: Super Contributor
timestamp: April 10, 2023, 02:03:53 am
content: I respectfully say no, they are not inexpensive or commonplace in North America and many fuse manufacturers here don't even bother making them. Years ago I had to special order them for customers returning from the UK running devices off a 120-240 transformer here. Is BS1362 relevent in your homeland or Germany as well? IDK ordering them for multimeter use, the mini ANENG fuses [urkl=https://www.aliexpress.com/item/4000375930617.html]3.5*10mm "ceramic British plug fuse"are a special order as well.The required interrupt rating is up in the air. Spec is different between UL and IEC standards. This is another trap I guess with smaller sized fuses. I have not read the IEC test for interrupt compared with UL, that could even be different.UL 248 seems to be 10kA/125VAC and IEC 60127 1.5kA/250VAC, likely Cat. II residential branch circuits but I'd have to dig for that.It looks like size matters and at least 20-32mm length is needed, even when sand-filled.

author: Someone
author_rank: Super Contributor
timestamp: April 10, 2023, 02:39:55 am
content: Quote from: DX1 on April 09, 2023, 05:57:42 pmHousehold wiring, already CAT IIIhttps://www.worksafe.qld.gov.au/news-and-events/newsletters/esafe-newsletters/esafe-editions/esafe-electrical/2022-newsletters/june-2022/multimeter-incidentslol, $100 for a guide to select a multimeterQuote from: tooki on April 09, 2023, 06:04:04 pmAttachment below, having escaped the paywall. But obvious and clear documentation is a standards requirement....

author: Fungus
author_rank: Super Contributor
timestamp: April 10, 2023, 03:31:32 am
content: Quote from: floobydust on April 10, 2023, 02:03:53 amMost multimeter fuses have to be ordered specially.The problem with Fluke-type fuses is that they're so low volume and lucrative that the market isfloodedwith fakes. There's no way to trust ordinary sellers and buying from somewhere "reputable" will double the already-outrageous price.BS1362 are almost as cheap as glass fuses and there's thousands of legitimate manufacturers for the fakers to compete with. Less profit=less fakery.Quote from: floobydust on April 10, 2023, 02:03:53 amI don't know why Aneng use those ridiculously small special fuses, or why they don't use BS1362. You'd think BS1362 would be a no-brainer for somebody trying to save pennies.PS: Those are NOT "British plug" fuses. British fuses are one inch long (what else would they be?)

author: DC1MC
author_rank: Super Contributor
timestamp: April 10, 2023, 05:42:29 am
content: Well, I guess that was it ? If the discussion devolved in savant debates about fuses, then I believe that there is nothing more to say about SZ20?This being said, I will close it permanently later today and let it run as it is, with good or bad, you have some pictures, EEPROM dump so this should be enough for everybody.Cheers,DC1MC

author: DC1MC
author_rank: Super Contributor
timestamp: April 10, 2023, 05:49:43 am
content: Here's another average resolution picture, if you can say where the TX UART pin is ? If you say that there's the one with a via in between the pads of U2, there is not, this one is going to the keys.

author: Gyro
author_rank: Super Contributor
timestamp: April 10, 2023, 10:21:27 am
content: Sorry for another minor diversion, but as it relates to CAT rating rather than fuses specifically...Quote from: Someone on April 10, 2023, 02:39:55 amThey really seem to have messed up that diagram. The table is appropriate to the CAT rating requirements, but the way it translates to what is shown on the diagram isn't. There's no way that the house socket wiring can be CAT III and then magically transform to CAT II as it comes out of the socket outlet (apart from maybe the UK with fused plugs - and even then the transition would occur in the plug, not the socket outlet).The diagram doesn't give sufficient clarity and granularity: They should have distinguished it as follows...- Distribution lines and feed into the house: Most definitely CAT IV teritory, no (relevant) overcurrent protection, those lines could be feeding an entire street and fed by a multi kA fuse.- They haven't defined the 'Meter Board' correctly. The Meter board is property of the energy supplier. It terminated the incomming feed, immediately fusing it down (typically 80-100A in the UK, I don't know about AUS) and holds the supplier's Electicity meter. The supplier fuse provides protection that takes the environment down to CAT III.- They have missed out theConsumer unit / Distribution board / fuse panel, depending on terminology. This is the home owner's property. The tails from the Meter into the unit and internal bus bar(s) are still at CAT III. The Consumer unit contains fuses, or hopefully breakers, protecting individual circuits down to the lower current required for their use and wiring capacity. The circuits that leave the consumer unit are at CAT II... There is no magical transition at the socket outlets.You might have hoped that a paywalled document would be a bit clearer.

author: Someone
author_rank: Super Contributor
timestamp: April 10, 2023, 10:32:13 am
content: Quote from: Gyro on April 10, 2023, 10:21:27 amNot really, things that plugs into the mains are CAT II, while the power socket is CAT III. Your UK centric (only?) view is really unrepresentative of the rest of the world.

author: Gyro
author_rank: Super Contributor
timestamp: April 10, 2023, 10:35:59 am
content: Quote from: Someone on April 10, 2023, 10:32:13 amWhat's the electrical difference (in fault current terms) between the wiring going into the socket and the plug coming out of it then? There are only bits of copper / brass inside the plug and socket. You are implying that the circuit is CAT III right the way into the consumer equipment. Edit: (Which is not what the diagram shows)P.S. I don't think there is anything UK centric about what I described (you can ignore the fused plug bit as it isn't particularly relevant in this context), it's pretty much international. I'd be interested in how your installation differs.

author: Someone
author_rank: Super Contributor
timestamp: April 10, 2023, 11:34:16 am
content: Quote from: Gyro on April 10, 2023, 10:35:59 amAll the detail you rely on is pretty much UK specific. EN/BS/AS/ANSI/UL/etc 61010 (the standard measurement categories come from) sets it plainly and in an internationally uniform manner.Appliances that plug into the distribution do not have the same heavy conductors, and are required to have sensibly low fusing currents so their fault currents are lower. Completely obvious to anyone who deals with the standards or went through training on these topics. Why try and make "clever" arguments about where the boundary should be defined, leading to yet another thread full of confusing and misleading content that beginners cant pick apart from the truth. You want to be a pedantic internet point winner? great have at, but don't try and pretend that is something more authoritative or useful than the international standards.

author: Gyro
author_rank: Super Contributor
timestamp: April 10, 2023, 12:28:14 pm
content: No clever arguments. The wall wiring and appliance cable are the same in terms of fault current that you would expect. The breakers within the distribution board (or whatever you might call it internationally) will limit the fault current to way below the 25kA they are talking about on CAT III final circuits. In countries that have no plug fuse (and that's the only UK reference I'm going to make) [Edit: the appliance lead] must be rated to handle the full final circuit breaker current in fault situations. I don't know about the low fusing currents you are referring to - if they are the ones in the consumer unit / distribution unit or whatever, then they apply to both the socket circuit wiringandthe appliance cord. Any internal appliance fusing is there to protect against appliance fire, not the mains cabling.Pleasedon't do the 'training on these topics', 'pretend to be authoritative' thing. I have designed industrial stuff for a living, have you?Again please clarify how different parts of thesamecircuit on thesamefinal circuit fuse / breaker can have different fault current - you really can't sensibly be putting it down to the thickness of the wire.

author: DC1MC
author_rank: Super Contributor
timestamp: April 10, 2023, 01:00:14 pm
content: For the dear love of Jesus, this was a thread about ANGENG SZ20, that is now covered in sterile, off-topic discussions of bloody fuses, obscuring anything about the poor multimeter.Now that you've buried in two pages of unrelated posts, could you gentle beings move this circus somewhere else, eventually on a special thread that I'm sure it will have 100+ pages in no time, please, please with cherry on top.Seriously disgruntled,DC1MC

author: Gyro
author_rank: Super Contributor
timestamp: April 10, 2023, 01:13:31 pm
content: My apologies DC1MC, That was intended to be a quick comment.

author: floobydust
author_rank: Super Contributor
timestamp: April 10, 2023, 06:09:51 pm
content: Sorry for drifting. I was wrong about the UART pin, compared to other COB which have different pinout.I think the DreamTech DTM0660L is just a firmware load for HyconHY12P65family. No idea why the same part gets more A/D counts.Pin 17 PT1.7/BZ/PSDO is for GPIO, buzzer output, PSD0 port for OTP R/W interface.Pin 18 PT1.6 EEPROM SCLPin 19 PT1.5 EEPROM SDAPin 20 PT1.4/TX is for GPIO, UART TXD. *This is the one to scope. Goes to via under EEPROM then to ?Pin 21 PT1.3/RX is for DI, UART RXD. This has a jumper to GND for Calibration Mode on older DTM0660.OTP appears to be synchronous serial with PSCK, PSDI, PSDO.The SZ-20 has pads for PT1.0, PT1.1 which are likely the function switch and pushbuttons. There has to be a way for automated calibration on a bed-of-nails and thus serial data, unless this is done using some kind of magic. Dreamtech/ANENG would sell a lot more if they opened up the data on these.

author: DC1MC
author_rank: Super Contributor
timestamp: April 10, 2023, 07:11:04 pm
content: Quote from: floobydust on April 10, 2023, 06:09:51 pmWell, the pins are exactly as I traced them, except TX is actually going to the keys, maybe I'm getting blind, if you can point on the last picture I published here, that is a close-up of of the MCU area, it will be nice, my guess was the pin that goes to the via between U2 pads, but this one goes to keyboard. For bed of nails calibration it may have been enough, but for logging is not usable, and most likely it was reassigned in the ROM as GPIO.To make things worse the EEPROM content (also posted) make no sense compared with the datasheet and other EEPROM dumps, so have no idea how to enable the logging.I guess that there is not too much that could be done, I hoping for someone to jump with some ideas and me being the hands to implement them, but nobody jumped in.DC1MCRxD is connected to the EEPROM WP and the corresponding resistor is missing, see the pictures, probably they've found a way to calibrate it like that and use the missing R pads as jumper because it was a bit of sloppy rework flux there.

author: Someone
author_rank: Super Contributor
timestamp: April 10, 2023, 11:28:35 pm
content: Quote from: Gyro on April 10, 2023, 12:28:14 pmI follow the standards, they're a collection of knowledge spanning far more than my experience..... which includes electrical apprenticeship and designing (Abrand) test and measurement equipment (to 61010).Quote from: Gyro on April 10, 2023, 12:28:14 pmNo, they don't. Please do provide a reference for that, because the references I have here (61010, 60335 , 62368, etc) certainly do not require appliance leads to support either the prospective fault current or even the maximum permissible hold current of an arbitrary power point/socket outlet. 0.75mm2 cables terminated with C13 plugs are pretty typical, around the office here they are the majority, and have test approvals and in service test tags that are current.Quote from: Gyro on April 10, 2023, 12:28:14 pmNone? Why try and redefine the boundaries of CAT II, CAT III, and CAT IV ? Then dig in and make all sort of noise about things you clearly know very little about? Safety isn't the place to try and find loopholes, or muddy the water with your plainly incorrect misleading and heading into dangerous claims.CAT III includes the wall mounted socket outlet, that's what 61010 defines. It's like trying to argue about the arbitrary steps in EMC regulations, 229MHz emissions affects things almost the same as 231MHz.... except 55011/55022/etc standards have 230MHz as a boundary between different requirements so they are treated differently. There may only be a slight distinction in reality between either side of a socket outlet in worst case conditions, yet there is a significant difference in most conditions. The line between different categories has to be drawn somewhere and the boundary of fixed wiring is easily recognisable, I think that is a pretty good place for the distinction.Quote from: DC1MC on April 10, 2023, 01:00:14 pm.. and the OP asking why CAT ratings are required, apparently without realising where those ratings are applicable.

author: DC1MC
author_rank: Super Contributor
timestamp: April 15, 2023, 01:56:46 pm
content: Before reassembling it I'm posting two top pictures with the detail of the LCD area that is usually covered when LCD is installed. Afterwards if it still work, I will try to do some precision measurements and that is the last time when you'll hear about this device from me, afterwards let the fuses, CAT ratings and building cabling penile measuring contests begin in full.Cheers,DC1MC

author: DC1MC
author_rank: Super Contributor
timestamp: April 15, 2023, 02:35:47 pm
content: Well, it survived resoldering the EEPROM and repacking, I've measured against the few precision resistor and voltage source and it's spot-on, if someone in DE (dr. Kleinstein, u.a) wants to spend some time characterizing it against some real stuff, please PM me.THE END

author: mzzj
author_rank: Super Contributor
timestamp: April 15, 2023, 03:32:15 pm
content: Quote from: Gyro on April 10, 2023, 10:21:27 amRating pic is bit misleading or overkill for household short circuit currents. Yeah, maybe for 30 story condo the short circuit currents next to distribution panel can be at that level.There is quite bit of difference between 1-family house and 1MW transformer switchboard.In here typical feeder to single-family house has 300 to 1000A short circuit current. Typical circuit breakers are rated at 6kA max breaking capacity.5kA short-circuit current would be reasonable expectation in installations with 3x200A or larger fusing nearby.

author: floobydust
author_rank: Super Contributor
timestamp: April 15, 2023, 03:54:07 pm
content: I would be interested in the display quality - contrast and update rate. Both looked not so great.The fake Cat. III, Cat. IV claims we are all used to as an ongoing dishonesty with chinese multimeters. I'm not sure why they just don't quit that and mark it "1,000V max." or something like they did in the 1980's lol.Remember on ACV it is DC-coupled so the op-amps will saturate if DC is present while on ACV. After the op-amp, there is a coupling capacitor to the ADC so the multimeter never knows it's clipping. I had some strange firmware behaviour, the autoranging also malfunctions last time I played with this, on other products using the DreamTech DMM IC.The test was measuring 0.1VAC 1kHz on something like 5VDC to flush it out.

author: DC1MC
author_rank: Super Contributor
timestamp: April 15, 2023, 04:25:04 pm
content: Well, the display is not the most perfect, is mediocre but legible. On the other hand I find the refresh rate perfectly acceptable and compatible with the Fluke 8060A. If you have any idea on how to make evaluation pictures I'm all for, unfortunately I don't have any high-end LCD devices, I can try to check at different angles to see if it fades away.I think I can inject 0.1V 1KHz AC over 5V, what should be the result ?

author: Fungus
author_rank: Super Contributor
timestamp: April 15, 2023, 06:58:06 pm
content: Quote from: floobydust on April 15, 2023, 03:54:07 pmIt's an arms race. Don't expect anybody to unilaterally stop putting it on their meters.

author: floobydust
author_rank: Super Contributor
timestamp: April 15, 2023, 07:45:34 pm
content: It's all fine until someone loses an eye, or maybe it goes nuclear... many such lumens. Sure honorable Mr. Zhejiang would agree.It is advertised to measure ACV and DCV at the same time so it doesn't have that old AC+DC limitation? 0.2% basic DCV accuracy, silicone boot (some offerings), A jack LED warning and more. It is a jump up in features, counts.In review videos the Ohms function is a little sluggish to autorange and displays a 1/2 value or two before settling. It can measure 250MEG as 00250.0LCD contrast is still unknown...

author: Someone
author_rank: Super Contributor
timestamp: April 15, 2023, 11:21:43 pm
content: Quote from: mzzj on April 15, 2023, 03:32:15 pmSure, that is your installation or typical. So now go around the world and tag out/de-energize anything that doesnt meetyourmagical new standard. 61010 is an international standard that covers almost worst case situations for the safety of the operator (who probably hasn't measured the fault current capacity before starting work, and if they had its the chicken and egg question of which rating should the fault current meter have?). CAT ratings have multiple dimensions that need to be satisfied, there might be absolutely zero real world installations at the corners of those dimensions but the limits are set to contain almost every conceivable situation.

author: Kleinstein
author_rank: Super Contributor
timestamp: April 16, 2023, 08:06:23 am
content: Having a mixed AC + DC signal and also AC frequencies higher than the digital RMS part can handle can lead to odd results. Quite some meters have problems with this - not just the cheap ones and may not detect clipping at some point in the signal chain. Sometimes a manual range selection helps.I just had an oscillating voltage regulator and my UT139 meter (uses digital RMS up to only some 1 kHz - so similar to this meter) did not show any AC reading - just no result, which is still better than some wrong value. In other examples one can also get wrong readings or an somewhat unexpected overload from the DC background (AC mV range).

author: DC1MC
author_rank: Super Contributor
timestamp: April 16, 2023, 09:44:07 am
content: Quote from: Kleinstein on April 16, 2023, 08:06:23 amSo, do you have interest in interrogatemy SZ20 for science, I can DHL it to you immediately, I'm actually curious on how good or bad it is ? You can subject it to any abuse you see fit, if it doesn't survive, than it wasn't worth.Cheers,DC1MC

author: Aldo22
author_rank: Super Contributor
timestamp: September 04, 2024, 02:53:52 pm
content: I got a Zoyi ZT-225 yesterday and took a few measurements. There are still a few open questions in this thread. E.g. the AC+DC mode and small voltages.Compared to the AN870, the ZT-225 (or Aneng SZ-20) is even thicker and needs 3 AA batteries.But there is a "triple display", which is quite practical.Whether the 25000 counts are really more useful than the 19999 on the AN870 is questionable with the same precision.I have attached a few pictures of the AC+DC mode and a measurement of 200µV.It's all in one picture: signal generator (right), oscilloscope measurement and (copied in) the measurement of the ZT-255.At frequencies below 2kHz sine this works quite well (zt255_1V_100mv.png, zt255_1V_1V.png).It does not see "noise" in the mV range (zt255_1V_100mv_noise.png)The 200µV come from a 200mV source with a self-made 60dB attenuator. It's not bad at all for that (200microvolt.jpg)Of course, this is just an impression. I don't have the instruments for more precise measurements.EDIT: 5µV image added. (50mV with 80dB attenuator). Seems to work.

author: Gyro
author_rank: Super Contributor
timestamp: September 04, 2024, 08:07:10 pm
content: It's a shame about that +/- 5uV dead zone. It would make a nice cheap null meter otherwise.

author: Aldo22
author_rank: Super Contributor
timestamp: September 05, 2024, 07:06:31 am
content: Quote from: Gyro on September 04, 2024, 08:07:10 pmYes, but with an accuracy of±(0.05%+3), the reading would be inaccurate anyway.But it is still an impressive DMM for the price. I paid CHF 22.50 including delivery.EDIT: By the way, it really is a monster. I hadn't expected it to be this fat.The picture shows a comparison with AN8008 and AN870. The AN870 is not really a pocket DMM either...But it looks like it could fall off the table a few times without being damaged, which doesn't happen quickly because it "sticks" to the surface quite well with its rubber-like casing.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 11, 2025, 02:23:04 am
content: Hello am looking at acquiring this DMM and while i know that its known as either a Zoyi ZT-225 or Aneng SZ20 i dont know if they are 100% the exact same device, does aneng do anything different to it?is the firmware any different ?is the calibration any worse or better ?is their QA any bettermaybe the leads included with the aneng are better idkare the specs any different (up to how many ohms or farads it can read)currently on AE the price for both units with shipping cost included is:$39 USD for the Zoyi$45 USD for the "base" aneng$52 USD for the "pro" version (which is just some extra leads and adapters)however the aneng listing has the checkmark of it being an official brand/genuine product has has much higher salies compared to the zoyi listing so maybe the warranty is better ?600+ sales for aneng and just 120 for the zoyi

author: Fungus
author_rank: Super Contributor
timestamp: January 11, 2025, 02:35:42 am
content: Quote from: Cosmic_Starlight on January 11, 2025, 02:23:04 amNo.

author: Aldo22
author_rank: Super Contributor
timestamp: January 11, 2025, 07:17:36 am
content: Quote from: Cosmic_Starlight on January 11, 2025, 02:23:04 amI don't think there is a technical difference.There is the obvious design difference that the Aneng has a colored ring and the Zoyi is black.I have the Zoyi because the Aneng is too colorful for my taste.Great DMM for electronics.https://www.aliexpress.com/item/1005007244323221.htmlhttps://zotektools.com/products/zoyi-zt-225/

author: Aldo22
author_rank: Super Contributor
timestamp: January 11, 2025, 01:53:08 pm
content: Btw. the only difference in the specs is, that the Aneng specifies an accuracy of DCV ± (0.2%+10), while the Zoyi specifies DCV ± (0.05%+3).I believe this is a typo in the Aneng specs. It also does not really match the ACV ± (0.3%+3).According to my measurements, the ZT-225 is more accurate than DCV ± (0.2%+10).

author: Paul T
author_rank: Regular Contributor
timestamp: January 18, 2025, 05:25:10 pm
content: If you would like to know how the SZ20's accuracy is across different measures, and compared to other devices like the AN870, check out the graphs I posted at KOT:https://www.keepontesting.com/post/error-chart-compilation-dc-voltagehttps://www.keepontesting.com/post/error-chart-compilation-dc-currenthttps://www.keepontesting.com/post/error-chart-compilation-resistancehttps://www.keepontesting.com/post/error-chart-compilation-capacitanceOne caveat, I noticed DCV measures further from spec when in the dual measurement mode (AC+DC). If you don't care about AC, be sure to have it in the DCV mode for best accuracy.

author: Aldo22
author_rank: Super Contributor
timestamp: January 18, 2025, 05:43:53 pm
content: Quote from: Paul T on January 18, 2025, 05:25:10 pmDo you really mean specs?Because the specifications are different for AC+DC modes anyway (See page 22).

author: Paul T
author_rank: Regular Contributor
timestamp: January 18, 2025, 05:53:54 pm
content: Quote from: Aldo22 on January 18, 2025, 05:43:53 pmI meant further from target.

author: Aldo22
author_rank: Super Contributor
timestamp: January 18, 2025, 05:59:43 pm
content: Quote from: Paul T on January 18, 2025, 05:53:54 pmThat's OK if it's within specs?

author: Paul T
author_rank: Regular Contributor
timestamp: January 18, 2025, 07:01:53 pm
content: Here's some snapshots of low current in a daisy chain. The numbers tend to wander up and down 2 counts on all meters. Not together in the same direction (it's not the current source). I did my best to capture the average condition. (Sort of like getting everyone to smile at the same time for a group picture)

author: Aldo22
author_rank: Super Contributor
timestamp: January 18, 2025, 07:58:15 pm
content: I have almost the same ones.They are all nice meters for very little money.

author: Paul T
author_rank: Regular Contributor
timestamp: January 18, 2025, 09:39:46 pm
content: Quote from: Aldo22 on January 18, 2025, 07:58:15 pmThat’s also true of my Keithley 220 current source. It was a dumpster dive. Dave would be proud if he saw this!

author: Aldo22
author_rank: Super Contributor
timestamp: January 18, 2025, 10:39:12 pm
content: Quote from: Paul T on January 18, 2025, 09:39:46 pmYes, the Keithley looks very good.I used the little $40 Fnirsi.For the price, it's quite reasonable.

author: Paul T
author_rank: Regular Contributor
timestamp: January 19, 2025, 12:31:16 am
content: These little signal generators are portable and convenient. I think you could stuff 24 of them inside the box for the keithley!I paid US$14.55 for this one.

author: Aldo22
author_rank: Super Contributor
timestamp: January 19, 2025, 09:54:58 am
content: One difference between the AN870 and the ZT-225 (SZ20) that I have noticed is the stability in the lower mVAC range.While the ZT-225 shows rock solid readings e.g. at 100µVAC@1kHz sine, the AN870 dances back and forth. Sometimes it hits the value, but you can't rely on it.Maybe the ZT-225 has better noise filters or does a different averaging.Attached is an example for 100µVAC@1kHz

author: Paul T
author_rank: Regular Contributor
timestamp: January 19, 2025, 12:23:11 pm
content: So it doesn't hold the Hz value on the screen?Another difference is the lack of electronic manual for the SZ20. One can be downloaded athttps://zotektools.com/products/zoyi-zt-225/Which makes me wonder, how do you get support for the ANENG?The larger tolerance on AC-DC mode is not listed on sales pages. Here's an example. That's why I specifically mentioned it here. It was a surprise to me and might be for others.

author: Aldo22
author_rank: Super Contributor
timestamp: January 19, 2025, 01:08:45 pm
content: Quote from: Paul T on January 19, 2025, 12:23:11 pmThere is no Hz value on the screen below 100mV in VAC mode.mVAC mode does not have a Hz dual display anyway.I meant, the mVAC value itself fluctuates with the AN870 while it is stable with the ZT-225Quote from: Paul T on January 19, 2025, 12:23:11 pmIt's the same. There is no brand or model name in the manual.Quote from: Paul T on January 19, 2025, 12:23:11 pmIt's a typo imho. +-(0.2%+10) for VDC is not what the manual says: +-(0.05%+3)

author: Paul T
author_rank: Regular Contributor
timestamp: January 19, 2025, 04:53:14 pm
content: The AC-DC mode loses DC accuracy at lower voltages as shown in the attached graph. It even reported -0.0003 at 0.0015 VDC.The graphs are not comparing values to the supply, it's the reported value after the range selector was changed.BTW, the SZ20 has a very high input impedance in the mV mode. Same with the AN870 and AN8009. Over 200 Megs I believe.

author: Aldo22
author_rank: Super Contributor
timestamp: January 19, 2025, 05:20:18 pm
content: Quote from: Paul T on January 19, 2025, 04:53:14 pmI cannot reproduce this:mV DC: 2.0mVV AC/DC: 0.0019VV DC: 0.0019VIn this range, however, I would choose the mV setting anyway.

author: Paul T
author_rank: Regular Contributor
timestamp: January 19, 2025, 06:06:45 pm
content: Maybe these units have a difference in their sensitivity at low voltage.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 27, 2025, 03:11:53 am
content: so my ZT-225 arrived yesterday, and for the most part everything looks ok and works ok theres only one or two issues1. temperature seems to read 1-3c higher than it should (not that i care that much but still outside spec for what the manual says)2. the frequency measurement doesnt seem to work at all (it only works if i use a phone app to generate a sine wave audio tone in this scenario it can read from 2hz up to 22khz spot on)but if i use any of my two GM328 units k and m firmware to generate any frequency it wont read it at all, it reads values at around 300khz3. the duty cycle in that same function as the frequency one is also messed up, using the same gm328 to generate a pwm signal at 0% it reads around 50% at 50% pwm it reads around 70% it only gets somewhat accurate at like 95% pwmso idk what i should do, i could ask for a full refund but i might get asked to return the item (which is another problem on its own, ive heard local reports of it taking 3 months to go back and then not getting a refund due to seller refusing the packageor just ask for a partial one of 50-75% of original purchase value, since those two functions seems to ve severely miss-calibrated or just bad i assume i cant trust too much the values it says on the other functionsany advice is greatly appreciated

author: Paul T
author_rank: Regular Contributor
timestamp: January 27, 2025, 03:31:36 am
content: Did you use the external temperature probe or internal sensor? Internal sensors tend to be less accurate than the external sensor. Plus, the external probe will work better when immersed sufficiently deep into agitated liquid than they do in still air.You might want to check with an oscilloscope where the source frequency crosses the 0V line. What is the P-P value? Any DC offset? The duty cycle function tends to calculate based on zero crossing point, and frequency requires over 100 mV RMS. Higher frequency detection will usually require higher voltage. TTL signals are sometimes not recognized at all by some devices due to lack of zero crossing.Are you using the AC function (high voltage low frequency), or Hz function (low voltage, high frequency)?I don’t know your experience or equipment or conditions. If there is no rush to return the item, keep trying different scenarios. An ice bath for temperature, a blocking capacitor for frequency, etc. The user manual unfortunately doesn't typically spell out best practice when using their functions. They mostly tell you how to insert leads, set the dial, and push some buttons.I personally use other devices for frequency and temperature. In my opinion, these are not core functions, and reflect the manufacturer's effort to put everything we want into one device to sell more units.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 27, 2025, 04:03:17 am
content: external probe and internal sensor measure about the same, unfortunately i do not own an oscilloscope, and am using the hz function low voltage high frequency, the only way i have to check the high voltage low frequency is mains and that seems to work okthere's no rush per se to return it but since i saw on a video review of the SZ20 by a Spanish guy and he specifically used a gm328 to measure the pwm signal and it measured the duty cycle correctly and i copied his test on mine and the values were all wrong it would lead me to believe that either the high freq/low voltage function is not properly calibrated or is just simply badso i dont know if i should talk to the seller and given they are supposedly the official zoyi store if they know if this thing has any sort of autocal that might fix itor straight up ask for a refund since i am not sure i can trust the accuracy of the rest of the functionsalso idk about the other buyers but my leads came in the bag but it wasnt sealed rather stapled closed, also the warning sticker that was supposed to come covering the amp jacks was not on the dmm itself but on the bag for the thermocoupleEDIT **and yeah while temperature its not a big issue and is an extra i can alway subtract 2 or 3 degress of whatever am meassuringbut if the low voltage high,freq doesnt work because its not properly calibrated how can i as an user trust the other functions meassurements ?

author: mwb1100
author_rank: Frequent Contributor
timestamp: January 27, 2025, 05:50:13 am
content: Quote from: Cosmic_Starlight on January 27, 2025, 03:11:53 amI don't know if it's true for others, but my experience with multimeter temperature measurements is that they nearly always are 1-3 degrees off of what my other thermometers (or multimeters) read. I attribute this to:- my other thermometers aren't "lab grade" by any means, so I suspect they may have 1-3 degree range of error too- multimeter manufacturers always have a disclaimer about temperature accuracy specs something along the lines of "the specs apply to the meter alone and do not take into account any error that the thermocouple may introduce". I have no idea how much error thermocouples might introduce.I don't worry too much about this because I generally don't care about precise temperatures - I'm usually interested in one of two things: 1) how much is the temperature changing, or 2) is the temperature too hot. Since "too hot" is generally a largerish number, +/- a couple degrees doesn't really matter.I like to test a meter's temperature measurement with an ice water bath and some water fresh from a boiling pot. But I still expect +/- a couple degrees to show.Quote from: Cosmic_Starlight on January 27, 2025, 03:11:53 amFrequency measurement (and the closely related duty cycle) often needs to have a zero crossing for the meter to perform the measurement. That often isn't clearly stated in the manual (particularly for low end meters like Aneng) and many (most?) reviews don't look for this. Also the signal might need to have a minimum voltage amplitude to be met before the meter can read the frequency. I don't know how the gm328's signal behaves.Update:I took a look at the manual for theZoyi ZT225. There' no mention of whether or not a zero crossing is needed for the frequency measurement. And the temperature spec is "±(3%+5)". Since there''s a ±5 counts in that specification the meter would technically be in spec as long as the reading was within 5 degrees of reality. So being off by 3C is actually within the spec. I believe that ±3, 4 or 5 counts on low end meter temperature specs is pretty common.

author: Fungus
author_rank: Super Contributor
timestamp: January 27, 2025, 06:20:09 am
content: Quote from: mwb1100 on January 27, 2025, 05:50:13 amThis ^

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 27, 2025, 06:39:26 am
content: Quote from: mwb1100 on January 27, 2025, 05:50:13 amwhile the temperature thing i really dont mind at all, the frequency counter and duty cycle function not working properly it is for me, while i do not have any specialty equipment to actually test under what conditions it can work or notfor example the gm328 user manual all it specifies is that its a square wave signal up to 1/4 of the mcu's speedof the yt reviews that did frequency meassurement the only one i can replicate is the one from the guy that used a gm328, in this one he used the 10 bit pwm generator from k firmware and he meassured using zif socket pins 1-3 (i know the device has dedicated pins for this) but i wanted to replicated exactly as he did, and for example his reads 7.8khz and duty cycle perfectly while mine either doesnt read anything or reads 300khz and a totally wrong duty cycleso since the high voltage low freq seems to work well enough i would assume someone at the factory messed up and didnt calibrate the low voltage high frequency on my meter correctlyEDIT **even when i have pwm to 0% or frequency generation to 0hz its still reading a frequency when i think its not supposed to (i know the pwm generation works correctly by putting a led on the pwm output and it lights up more brightly as the pwm duty cycle is increased)

author: puxe
author_rank: Contributor
timestamp: January 27, 2025, 08:25:16 am
content: If you are considering returning a faulty item from AliExpress, I would be careful.Of the two items I returned, one was refunded, but the UK postage was not, despite the item having arrived to the specified return address, with full Royal Mail tracking. The other item had to be returned from the UK to Germany and the recipient refused delivery. PayPal had to resolve the refund in the end as AliExpress platform did not honour their published return and guarantee policies.I'm out of pocket with these items and going forward I only buy items I'm prepared to write off. In the past I've bought oscilloscopes, binoculars and other items of reasonable value.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 27, 2025, 08:41:15 am
content: It is easy to verify if the frequency measurement isn't working properly because of lack of zero crossing. Insert a capacitor of about 100nF (value is not critical) between generator output and the red probe.

author: Aldo22
author_rank: Super Contributor
timestamp: January 27, 2025, 08:57:53 am
content: It works here with the GM328 signal, even if it is not zero crossing.Btw. an oscilloscope can be very informative in such cases.Even a $20 scope is better than no scope at all.

author: Paul T
author_rank: Regular Contributor
timestamp: January 27, 2025, 11:45:10 am
content: Quote from: puxe on January 27, 2025, 08:25:16 amTheir choice program is not as good as it was 2 months ago, and neither is their customer service. Something has happened - and as a result, I'm being very cautious too. I used to order in confidence, now I read through many of the reviews before buying.

author: puxe
author_rank: Contributor
timestamp: January 27, 2025, 12:00:55 pm
content: Quote from: Paul T on January 27, 2025, 11:45:10 amWhat makes the AliExpress process even more frustrating is that they give you the runaround and not only waste your money, but also lots of your time. Requesting screenshots of tracking information and postage labels more than once, that they then ignore ..... despite every customer service agent promising it will be escalated and resolved via a refund with return postage included.

author: Aldo22
author_rank: Super Contributor
timestamp: January 27, 2025, 12:06:01 pm
content: I have not yet returned anything to AE.I got a refund twice, once on the condition that I order the device again and then I get the wrong delivery refunded. That worked and I was allowed to keep the wrong delivery.Everything <$20. That was last year.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 27, 2025, 11:07:59 pm
content: Quote from: wasedadoc on January 27, 2025, 08:41:15 amWow it seems that was the problem, now frequency and duty cycle.work.correctly (it still goes crazy at 0% and at 100% pwm)But I guess is expected that it can't read voltage correctly with that 100nf cap in placeTried the next closes value which is 300nf film works about the same except at 0 and 100pwm it doesn't go crazy but goes to all zeroesAlso tried the next closes value I have which is a 300nf film cap, with this it doesn't go crazy at 0 and 100pwm it just goes to all zeroes nowEDIT **I used a 100nf ceramic cap its the only one I had of that value I would post more photos but I can't due to 8mb attachment limit

author: Aldo22
author_rank: Super Contributor
timestamp: January 27, 2025, 11:43:55 pm
content: Quote from: Cosmic_Starlight on January 27, 2025, 11:07:59 pmVAC measurement is accurate up to 2kHz. No chance at 25kHz.Quote from: Cosmic_Starlight on January 27, 2025, 11:07:59 pmWhy do you post such gigantic pictures?The image does not contain any information that requires a high resolution.Look, I have reduced your picture from 3MB to 126kB. You can still see everything.

author: Paul T
author_rank: Regular Contributor
timestamp: January 27, 2025, 11:47:02 pm
content: Somebody needs an oscilloscope.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 28, 2025, 12:08:49 am
content: Quote from: Cosmic_Starlight on January 27, 2025, 11:07:59 pmNo meter can work miracles at the extremes. A waveform with any peak-to-peak voltage and 0% duty cycle is exactly the same as a zero volt input with any duty cycle.

author: Fungus
author_rank: Super Contributor
timestamp: January 28, 2025, 12:47:16 am
content: One of those $30 Zeeweii oscilloscopes will give you far more info at far higher frequencies than any multimeter.

author: mwb1100
author_rank: Frequent Contributor
timestamp: January 28, 2025, 01:13:41 am
content: Quote from: Cosmic_Starlight on January 27, 2025, 11:07:59 pmGoogle search for "image compression" gets several websites that you can drag & drop photos onto to recompress them. If you want something that runs on your computer, I use the free Fileminimizer Pictures athttps://balesio.com/fileminimizerpictures/eng/index.php. It has some annoyances (like a nag to buy their minimizer suite) but overall works for me. I'm sure there are better options. One of these days I'll go looking for some open source command line thing...

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 28, 2025, 01:51:26 am
content: Quote from: Aldo22 on January 27, 2025, 11:43:55 pmi dont know, thats the size the phone saves photos at, usually in the 5-8mb range per photoQuote from: Paul T on January 27, 2025, 11:47:02 pmi will, i really want one but in due timeQuote from: wasedadoc on January 28, 2025, 12:08:49 amyeah i know that i really am not expecting this to work miracles and i know an osciloscope is the proper tool for the jobbut i was more wondering if it was me not knowing how to use that function or if there is something fundamentally wrong with the unit i goti really dont need professional grade or lab grade accuracy, the accuracy one of these units in full working order provides is more than enough for me, am not an electrical engineer nor am i designing any sort of circuit am i am more of a casual hobbyist that likes messing around with thingsbut now i know there is something fundamentally wrong with mine, maybe tomorrow i will try to take it apart and see if theres any component missing on the pcb or something burned or loose or somethingthere also a spanish guy on yt that had another issue with his in which his temperature function would be all over the place depending if he turned backlight on or of, hold function, max min, all those things made the shown temperature change so it seems the QC on these units is still lackingbut it seems the problem is purely software related ?! and theres little to nothing i can do to fix it ?i have attach the full set of photos now properly compressed

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 05:22:55 am
content: Quote from: Cosmic_Starlight on January 28, 2025, 01:51:26 amWhat is outside the specifications?As wasedadoc said, 0% and %100 duty cycle can't be measured anyway and the accuracy of external temperature measurement is specified (-20~1000)°C with ±(3%+5).This is not suitable for room temperature anyway.20°C could be read as 14.4°C or as 25.6°C and still be in specs.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 28, 2025, 07:07:52 am
content: Quote from: Aldo22 on January 28, 2025, 05:22:55 ami understand that however like you yourself showed, it should be perfectly capable of reading pwm signals from the gm328 by itself without the need to add 100nf cap into the mixthe temperature thing is perfectly clear an understandable am not arguing that one bit.the issue is that by itself it cannot read any frequency correctly or duty cycle correctly not even close(like if you were trying to measure 120v ac and the dmm showed 800v instead, its just like that, or trying to measure a 1k resistor and it showed 10M instead)unless i add a 100nf cap to the red probe.and from what wasedadoc said if i understood correctly if the frequency measurement isnt working properly because of lack of zero crossing adding a 100nf cap should fix it which in my case did and i dont think yours has that issue ?(did you just put both probes into the freq output or did you too had to add a 100nf cap too ?)but i cannot just open the dmm up and solder it in because at the very least voltage measurement will not work correctly hence my comment of "something being fundamentally wrong with mine"even the high voltage/low freq measurement with the 100nf cap in place works better than without itlook i am not pretending to know or understand everything, so far i know this dmm is perfectly capable of reading pwm and freq from the gm328 by itself from a yt video review and yourselfi just need a specific reason as to why the freq measurement is not working on my unit and works without issue on others with the same setupi cant just argue to the AE seller that the freq measurement doesnt work and leave it at that, i would like to have "a stronger case" and tell him this does not work because of this of this and that so in conclusion device is defective and measurements cannot be trusted(sorry for the wall of text i tend to do that since obviously english isnt my first language and thats one way i think i can make myself better understood)

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 08:33:55 am
content: I have had another look at it.It's true that it was able to measure the 10bit PWM signal in my case, but that's apparently a borderline case.The DMM does not need a “zerocrossing” signal as you would imagine from the word (i.e. that it takes negative values),butit must go tozeroat some point, otherwise it won't work for me either.However, certain signals of the GM328 do not do this (possibly in connection with input circuitry of the DMM).In the attached picture you can see 1MHz from the GM328.This signal has a positive offset and never gets to 0. My ZT-225 can't measure that either.So actually you would need an oscilloscope to see what is really going on before you can say what the problem is.This one is quite cheap and useful:https://www.aliexpress.com/item/1005007394192248.htmlFor the things you are trying to do, even an expensive DMM is inferior to a cheap oscilloscope.

author: Paul T
author_rank: Regular Contributor
timestamp: January 28, 2025, 11:43:18 am
content: @Aldo22 For the waveform shown, what is the duty cycle reported by the multimeter if you add -0.5v DC bias? Will it be 70%, 50%, or 30%? I'm wondering if duty cycle is related to the difference in time between positive zero crossing and negative zero crossing.As for not wanting to use a capacitor, well that's as stubborn as refusing to change the multimeter from DC to AC mode. It's simply a matter of understanding your potential circuit output and using the multimeter properly. Very common for a DMM to use zero crossing, maybe it's not as common for a DMM to not use a capacitor to block DC in Hz mode... I don't know.I have various multimeters which measure Hz, and only a few of them do frequency very well, without being picky. As a result, I feel an oscilloscope is a requirement for any electronics technician.Just one example of understanding your circuit. If you charge a battery from a low impedance benchtop power supply and don't use a diode in series, there is danger of having a short if the power supply is purposely or accidentally shut off. It's just the way it is, can't blame the power supply for being made wrong. It's a versatile device that isn't always a battery charger.There are many devices that detect using zero crossing. The ZOYI meter without a capacitor might reflect how those devices are working. If the capacitor was built in, you would never have the option to make the multimeter match the device's detection method.

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 12:30:57 pm
content: Quote from: Paul T on January 28, 2025, 11:43:18 amI tested it with the signal generator instead of the GM328.In the attached screenshot you see a triangle waveform with (approximately) 5Vpp and -1V offset.The ZT-225 shows 1.0000kHz and 29.5% duty.You can see that it measures the duty cycle above the zero line (everything not super accurate).

author: Paul T
author_rank: Regular Contributor
timestamp: January 28, 2025, 12:39:37 pm
content: Thanks @Aldo22.Looks like the duty cycle is % time above 0V. Add a blocking cap and it probably rises to 50%.Then there are more interesting cases where the wave isn't balanced, like rectification. Add a diode and capacitor? I digress....

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 02:16:56 pm
content: Yes, lots of questionsWhat I don't quite understand is the difference on the oscilloscope between AC RMS and DC RMS.My scope can display both values (see attached screenshot). DC RMS at the bottom and AC RMS in the window (This could be reversed if you change the coupling to AC).With this somewhat irregular waveform, AC RMS is almost half of DC RMS.The measurement of the ZT-225 corresponds more to the AC RMS value.I somehow realize that a DC offset is added to the AC RMS, but how is the offset defined here? I have not set an offset in the signal generator.Well, it's a Hantek, so maybe notthereference.

author: Paul T
author_rank: Regular Contributor
timestamp: January 28, 2025, 02:29:03 pm
content: DC RMS should be the integration of the total voltage through a complete cycle, divided by the period. Each integration point is the distance from the zero volt line to the position on the graph.AC RMS should be the integration of the change in voltage through a complete cycle, divided by the period. Each integration point is the distance from the average volt line to the relative position on the graph.I believe the RMS mathematics involves a square, so any negative values becomes a positive contribution.If you use a blocking capacitor, the AC and DC measures should be the same. This takes away the potential heating effect of the DC portion.

author: Aldo22
author_rank: Super Contributor
timestamp: January 28, 2025, 03:35:35 pm
content: Thank you!With AC coupling it looks like in the attachment.I had forgotten that the ZT-225 can also display both values.AC RMS is the normal value for AC measurement and DC RMS is the value for AC+DC.These are my measurements on the ZT-225:AC = 0.8370V (Hantek 0.839V)AC+DC = 1.690V (Hantek 1.66V)This is very close to the measurements on the oscilloscope.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 28, 2025, 07:09:34 pm
content: RMS equals the DC voltage that would cause the same amount of heat to be dissipated in the same resistor (of arbitrary value) as when the source being measured is applied.Amount of heat is independent of voltage polarity. Heat is power which is voltage times current ie proportional to voltage squared. That is the S in RMS.I have no doubt that the SZ20/ ZT-225 is working as designed.

author: wasedadoc
author_rank: Super Contributor
timestamp: January 28, 2025, 07:47:42 pm
content: Quote from: Paul T on January 28, 2025, 02:29:03 pmFirst two paragraphs are factually incorrect. No mention of squaring before the integration and the final root after the mean.

author: Paul T
author_rank: Regular Contributor
timestamp: January 28, 2025, 08:00:04 pm
content: Quote from: wasedadoc on January 28, 2025, 07:47:42 pmMy description wasn't made to be a math equation. I was only looking to make a simplistic point that the DC calculation is referenced to the absolute zero, and AC calculation is referenced to the averaged zero.Quote from: wasedadoc on January 28, 2025, 07:09:34 pm

author: wasedadoc
author_rank: Super Contributor
timestamp: January 28, 2025, 08:41:33 pm
content: Quote from: Paul T on January 28, 2025, 08:00:04 pmRMS meansRoot of theMean of theSquares.It is quite clear that the mean (=average) is performed on the squared valuesandthere is a final square root on that mean to yield the RMS value.Regarding your "The square is to ensure equal weighting of each integration value." What does "equal weighting" mean if not the "effectiveness" of any input voltage point on the waveform is proportional to its square? (Because RMS is about what that voltage can do in terms of power.)

author: wasedadoc
author_rank: Super Contributor
timestamp: January 28, 2025, 09:27:55 pm
content: Quote from: Paul T on January 28, 2025, 08:50:42 pmI pointed out some errors in one of your posts. Can you point out errors in mine?The formulae do not incorporate current and/or power because irrespective of the load they disappear in the final result.There is no "misapplication of the analogy".

author: Paul T
author_rank: Regular Contributor
timestamp: January 28, 2025, 09:53:16 pm
content: OK, in my subsequent discussion with you I forgot that either the RMS voltage or the RMS current is a special case by the unique definition that the average value is based on equal power dissipation through same resistor, requiring squaring for a non-calculus reason.If you want average power, you don't square the watt terms when adding. This is the type of case I am more familiar with.Regardless, the point I was making about AC vs DC is still valid. And the general method to determine it is as well. I did say "I believe the RMS mathematics involves a square" - which tells you I didn't forget everything I learned 40 years ago.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 29, 2025, 01:48:08 am
content: Quote from: Aldo22 on January 28, 2025, 08:33:55 amyeah i now understand that it has to go to 0v at some point in order for the dmm to read it, but my question for your particular unit if the voltage does not go to 0 at any point what does the dmm show ? all zeroes or some seemingly random value ?because mine without the 100nf cap it shows a seemingly random freq and a duty cycle of around 50-20% higher than the gm328 is generatingQuote from: Paul T on January 28, 2025, 11:43:18 amyeah fair enough, in the grand scheme of things adding a cap to the red probe isnt much problem, i also understand that the frequency or voltage or pwm signal has to get to zero at one pointwhat i dont understand yet, is why does my dmm specifically have to add a 100nf cap to red probe to read any frequency or duty cycle accurately when aldo22 doesnt have to ?also i just saw some videos of ppl testing the gm328 pwm signal with an osciloscope and they all showed min voltage was either 0v or a little into the minus range (it flickered a bit it wasnt always stable)its kind of like an envy of seeing two other people have theirs work out of the box and mine doesntfor ac signals (sine wave i believe they are) it works well enough, it can read the 60hz freq of mains at 120ac and another outlet in my house thats 240v 60hz no problem, also reads the sine wave audio signal from an rca jack from a phone generating a tone with 99-100% accuracyi will attach some photos of some more measurements i did today, showing what it measures with no capacitor and with a capacitor on.also idk why and idk if yours or anyone else's is the same but mine some times starts reading frequencies when the leads arent connected to anything the only fixes are either to short both leads together, disconnect the red lead from dmm, or hold it in my hand (i would hope thats just the dmm picking up background noise due to the dmm being unshielded)i also disassembled the unit and no parts were missing, however there were a couple of microscopic solder balls stuck to parts of the pcb that i removed, also theres some black gunk on the manually soldered parts idk whythe only difference between aldo's gm328 and the spanish guy with mine is that you both have the one known as "GM328A" which is black pcb solder mask and SMD components minus MCU thats DIP running at 8Mhz, and mine is the AY-AT which is only trough-hole components and also is running at 16Mhzhence why mine reads 15.6Khz in pwm modewhat i would please ask of you appealing to your knowledge is seeing what you have seen from my unit, and reading what i have said it does, would you say this unit has a defective and or uncalibrated frequency meassurement/duty cycle or everything is within normal parameters and it just cant read whatever the gm328 is generating ?i honestly dont wanna look like an ass to the AE seller for not knowing how to use a device

author: Aldo22
author_rank: Super Contributor
timestamp: January 29, 2025, 08:43:38 am
content: Quote from: Cosmic_Starlight on January 29, 2025, 01:48:08 amIt actually shows 0, but as soon as I touch the test leads with my finger, it settles at 50Hz after a while. This is very sluggish, it stays at 50Hz for a while even after I let go of the test leads.Do you have any interfering devices at your place?

author: Paul T
author_rank: Regular Contributor
timestamp: January 29, 2025, 10:37:47 am
content: The difference might be the blocking capacitor used (try other values for a different response).Frequency on open circuit connection - any devices the leads are running close to (LED lights?) What about the signal generator, is it plugged into a noisy power supply? I would expect a high impedance input with loose leads connected to the jacks is working like an antenna for noise. Try using shorter leads and taking the setup somewhere away from other electronics.A square wave is not the best type of wave for evaluation. Mathematically, it is the sum of many sinusoids at incremental harmonics. As the frequency goes higher, the device could potentially respond to harmonics more than the main frequency, because higher frequency = less sensitivity. The shape of the wave may be getting very distorted with your setup.Is it possible for you to generate a sinusoidal wave, which is less likely to distort, ring, or contain harmonics?What does the AC voltage measure at the different frequencies you are trying? Is the trend to get lower volts each time you double the frequency? Where exactly does everything fall apart, and how does that compare to the manual's response?

author: wasedadoc
author_rank: Super Contributor
timestamp: January 29, 2025, 09:32:46 pm
content: Quote from: Paul T on January 29, 2025, 10:37:47 amThat should be more (not less) sensitivity.

author: Paul T
author_rank: Regular Contributor
timestamp: January 29, 2025, 09:46:55 pm
content: Quote from: wasedadoc on January 29, 2025, 09:32:46 pmWhatever dude. If your are so smart, consider being helpful instead of trolling around this forum looking to find people to correct. Yes, I reviewed your recent posts and you obviously have something to prove.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 30, 2025, 01:43:33 am
content: Quote from: Aldo22 on January 29, 2025, 08:43:38 amQuote from: Paul T on January 29, 2025, 10:37:47 amso i took special atention at Paul's advice about a possible noisy power supply, and turns out that was the issue, so for example i had the connector and cable just laying on the table next to the DMM as soon as i connected it to mains it would start reading a frequency, and as soon as in unplugged it from mains the dmm was back to zeroso i borrowed a 9v battery from somewhere and powered the gm328 from that and now it could actually read freq and duty cycle correctly on its own !what i did noticed is that as the pwm frequency went up the duty cycle would read slightly higher, ie at 25khz 50% would be read as 50.7% but at say 10khz it would be read at 50.1%for some reason at the pwm/square wave outputs on the pcb there were some blind spots in the freq generation for example 800khz wouldnt be read at all, but if i tried instead red probe on zif 3 and black on zif 1 it would read them correctly and even the pwm from k firmware was dead centerhowever at max on its own it could only read up to 2Mhz anything above it wouldnt, lowest i could get was a little over 1hz, i tried lower than that but it would show it on the dmm from like half a second then go back to nothingadding the capacitor again it allowed it to read the full 4Mhzbut now another thing that has gotten me concerned is this:so i had this 1st GM328 unit that came deffective and i have someone online that has been helping me diagnose it telling me what he sees on his and how and what to testanyway one such test was to put red probe on zif socket 1 and black probe on groundon old DMM which is a UNI-T UT33A (old non plus version that has hfe measurement) it reads 23.35Mohmsand this new DMM the ZT-225 using the exact same leads reads 5.42Mohmsbut meassuring loose resistors both meassure about the same +- 1 or 2 ohmsso idk if i should be concerned or not

author: Paul T
author_rank: Regular Contributor
timestamp: January 30, 2025, 02:38:25 am
content: Quote from: Cosmic_Starlight on January 30, 2025, 01:43:33 amGlad you're getting some resolution!As for the two meters measuring the circuit, the two meters might influence the circuit's apparent resistance by their output voltage.According tohttps://lygte-info.dk/review/DMMUNI-T%20UT33A%2B%20UK.htmlthe output voltage is 1.0 V (open circuit) and the current (short circuit) 0.31 mA.For the ANENG SZ20, I measure 0.53 V and 0.43 mA.It usually takes around 0.6V to conduct through a semiconductor junction, so that may explain the difference.Or, if you mistakenly reversed the + and - terminals between devices. Polarity doesn't make a difference on resistors, but it does on semiconductors.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 30, 2025, 03:12:33 am
content: Quote from: Paul T on January 30, 2025, 02:38:25 ami took several measurements between 3 different multimeters and i very much took care to not have reversed the leadsUT33A non plus 23.35MohmsZT-225 5.42Mohmsrebranded UT33C non plus (manual range) somewhere around 2.5Mohmssince i have the older version, i will measure its output voltage in resistance mode tomorrow and tell you (i just saw your link and it states the UT33A+ has diode voltage of up to 2.2v and ive measured mine to be up to 1.2v)also i tried measuring the impedance of both so i put both in resistance mode and tried measuring the ZT-225's resistance in resistance mode from the UT33A but only the ZT-225 showed a reading of about 11.5Mohms which is the same as trying to measure the UT33A impedance from the ZT-225 (so when both are measuring each other in resistance mode only the ZT-225 shows a reading the UT33A is still 0L)also by the same guy thats been helping me i was suggested i need a pure resistor and suggested a 10Mohms one and then i could compare both so i guess i could get one of those (but i wouldnt be too surprised if both measured the same still)

author: Aldo22
author_rank: Super Contributor
timestamp: January 30, 2025, 08:53:40 am
content: Quote from: Paul T on January 30, 2025, 02:38:25 amIt changes with the range.I measure approx. 520mV in the MΩ ranges and approx. 1V in all other ranges.When switching on the resistance measurement, it always goes to 1V for a short time.But yes, for MΩ measurement it is around 520mV in the end.I say this to avoid misunderstandings.

author: Paul T
author_rank: Regular Contributor
timestamp: January 30, 2025, 12:20:48 pm
content: Good point. The open circuit and short circuit measurements are only two end points on a broad spectrum of possibilities. The range isn't just changing what's displayed, it's also likely changing how it is acquired in order to provide the optimum current for the required resolution.When the resistance is unstable and keeps changing on the screen, it could be active components are responding to the voltage level with each range switch in ways that a resistor wouldn't.

author: Aldo22
author_rank: Super Contributor
timestamp: January 30, 2025, 02:17:19 pm
content: I measured the currents in different ranges (short).Ω 407μAkΩ1 87μAkΩ2 9.9μAkΩ3 1μAMΩ1 0.11μAMΩ2 0.11μAMΩ3 0.11μA

author: Paul T
author_rank: Regular Contributor
timestamp: January 30, 2025, 08:27:12 pm
content: Quote from: Aldo22 on January 30, 2025, 02:17:19 pmHi Aldo22, I had the same thought in mind. I just published a blog showing graphs of tests for different resistance. Check it out here:https://www.keepontesting.com/post/how-a-25-000-count-auto-ranging-multimeter-measures-resistanceI'm sure different multimeters use different "gears".

author: Paul T
author_rank: Regular Contributor
timestamp: January 30, 2025, 09:30:15 pm
content: Quote from: Cosmic_Starlight on January 30, 2025, 03:12:33 amAccording to my testing linked above, you can see the ANENG SZ20 test conditions for that range. The voltage drop for 5.26 Megohm was 0.3479 volts, very close to your test.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 30, 2025, 10:47:38 pm
content: Quote from: Aldo22 on January 30, 2025, 02:17:19 pmDiode voltage of the UT33A non plus is 1.3v compared to 2.2v of the plus versionSo the UT33A in ohms mode in the Mega range outputs around 0.232vZT-225 ohms 1.015v1st k range 1.014v2nd k 1.006v3rd k 0.931vall M 0.535vCurrentUT33A @100ohms 212.68uAZT-225ohms 368.6 UA1st k 100uA2nd k 9.9uA3rd k 0.9-1.0 uAM ohms too small to read (the UT33A flickers 000.1 for like 250ms)Quote from: Paul T on January 30, 2025, 09:30:15 pmAm sorry this all still flies way over my head should I be concerned about such a huge discrepancy in the gm328's circuit resistance between the two dmm ? Which one of the two is the right value ?

author: Paul T
author_rank: Regular Contributor
timestamp: January 30, 2025, 11:10:53 pm
content: Quote from: Cosmic_Starlight on January 30, 2025, 10:47:38 pmI believe you said someone recommended putting an ohmmeter across the terminals to diagnose an issue. Problem is, the resistance value reported depends on what meter you attach to it.Unless you use the exact same multimeter the other person is using, you could get a different result because of the way each ohmmeter was programmed to work. It sends out a test current, and sees a voltage drop which it can measure.Neither multimeter has the wrong value from what I can tell, because it's being used on a circuit that isn't passive. The components behind the output terminals of the GM3238 may react differently based on how much voltage and/or current is applied.See what happens when you measure the voltage drop across a diode using different multimeters. The voltage-current curve is not linear. Therefore, the curve's slope (resistance) detected depends what current you put in.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 30, 2025, 11:54:11 pm
content: Quote from: Paul T on January 30, 2025, 11:10:53 pmYeah you're right I just remembered that the diode drop reading on screen will depend on its output voltage but for such a big difference in diode voltage the difference doesn't seem that bigSo measuring diodesZT-225 3.2v1N4007 0.582v(Very Small transparent crystal like in appearance) 0.608vUT33A 1.36v1N4007 0.512vSame small crystal like 0.537UT33C rebranded 2.95v (this one idk if it's supposed to be voltage drop or resistance it doesn't have a way to select either like the other two also its starting to show low battery so readings are likely a little higher than usual)1N7004 706Same small crystal like 744So if I understand correctly I van only compare them with singlr passive components like resistors, voltage etc ?

author: Paul T
author_rank: Regular Contributor
timestamp: January 30, 2025, 11:58:19 pm
content: What is the ohms the meters report when measuring the resistance of diodes, forward biased of course.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: January 31, 2025, 12:39:40 am
content: Quote from: Paul T on January 30, 2025, 11:58:19 pm1N4007ZT-225 2.06MUT33A 4.55MUT33C 1.08M ?!Small crystal like ( measures resistance too in reverse but much higher)ZT-225 1.49MUT33A 712-723 KUT33C 910 K

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: February 02, 2025, 03:41:34 am
content: so i got some big value resistors today, the difference between old dmm and the ZT-225 is either 0.4 or 0.04 at max in the K range or M range (the ZT-225 being the one reading higher), and at the lower end of resistance by measuring a speaker the old one reads 3.9 and flickers to 4.0 and very briefly to 4.1, the ZT-225 is rock solid on 3.9 ohmsso i think its safe to say this dmm is good (fortunately)anyway i remember when i first stumbled upon this thread some people were asking about an autocal or some sort of calibration for this unitand googling around i found someone chinese guy that managed to calibrate his or access that mode after he had made some hardware modifications to his ZT-225 that required a re-calibrationits a BILIBILI video but it requires registration to even enable subtitles, also it seems it requires some sort of smd soldering/desoldering work (which i lack all the tools) from seeing some if his other videosalso saw two other videos from other zoyi dmm and the autucal was accessed trough a jumper/soldering two pads togetherhttps://www.bilibili.com/video/BV1oT2GYSEcG/

author: Aldo22
author_rank: Super Contributor
timestamp: February 02, 2025, 10:35:23 am
content: Quote from: Cosmic_Starlight on February 02, 2025, 03:41:34 amThat looks interesting. Unfortunately, I don't understand a word and can't tell from the video how he does it.Calibration would be nice to have.

author: Aldo22
author_rank: Super Contributor
timestamp: February 02, 2025, 10:54:46 am
content: I have found another fairly new video:https://youtu.be/xKDbI2wXe-gStrangely enough, the testers rarely mention a feature that distinguishes this meter from others in its class, including the AN870.The ZT-225 can show you the Vrms value that your scope shows you with DC-coupling.Other DMMs only show you the Vrms value as with AC-coupling, which is not necessarily the standard on an oscilloscope.In the example below, you see a 5Vpp square wave with +2.5V offset.Scope and DMM show approximately the same Vrms value. Other DMMs in this price range would only show 2.5Vrms.So if the scope and DMM are not in agreement: Turn on AC+DC mode on the ZT-225.

author: danno_cj
author_rank: Contributor
timestamp: February 02, 2025, 08:58:30 pm
content: Calibration is quite simple for this multimeter. First you must connect together those two pads from R29. Then from Off go directly to Ohm range and press two times SEL button to enter in calibration mode. Apply 100mV signal and press HOLD to confirm. Now move de switch to DC Volts and feed 10V signal and confirm with HOLD. In the video the user reference voltage was not exactly 10V, his source was 9.999V so the user pressed several times Hold buton until he lowered the value from 10.000 to 9.999. Maybe with another button is possible to raise the value if the voltage source is bit over 10V, I don't know. I would recommend to save the eeprom content before doing anything just to have a comeback way if something go wrong.Keep in mind the calibration needs a precise know voltage source and this meter may have not the best liniar precision or thermal stability. It may show exactly 10.000V but this precision can be worse with other values on the same range or in a different range. Also the values wrote on cheap Chinese voltage source can be off with some degree so the home calibration can do more harm.

author: Aldo22
author_rank: Super Contributor
timestamp: February 02, 2025, 10:33:23 pm
content: Thank you!It's good to know that this option exists.But you're right, I probably won't try it at the moment.My ZT-225 is within spec measured against the AD584L reference, except at 2.5V, but there all my DMMs are reading 2mV too low. I think the AD584L is not quite accurate there.Without a more accurate reference, recalibration probably makes no sense.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: February 03, 2025, 01:30:35 am
content: Quote from: danno_cj on February 02, 2025, 08:58:30 pmyou beat me to it lol, i just found those instructions too on a chinese forum not 1 hour ago, anyway its good to finally have precise and clear instructions just in caseQuote from: Aldo22 on February 02, 2025, 10:33:23 pmalso during my research the things ive seen the chinese do that i can remember from memory areaccess calibration moderemove flashlight led, or tie to a switchchange crystal from 4mhz to 8mhzmodify specific bits of an address of the eeprom for something about capacitance measurement (also using some math knowin what value the dmm is currently showing) and also various other thingssomething about changing a "front end capacitor" dunno if this was for speed or convergence or bothsomething about changing some resistors on the pcb for meassuremetsdimming the screen brighntess a bit by swapping some resistor on pcbswapping the voltage reference TO-92 for another one with a lower temperature drifti even saw a photo of one modified to have its backlight color be green insteadive attached a screenshot of what baidu's ai says users have modified about the unit

author: Paul T
author_rank: Regular Contributor
timestamp: February 03, 2025, 01:36:40 am
content: Quote from: Cosmic_Starlight on February 03, 2025, 01:30:35 amWho would do such a thing to a multimeter?

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: February 03, 2025, 01:41:35 am
content: for now all i will probably do it is probably just desolder the led "flashlight" since its damn near useless and would help to lower the power usage a bit when the backlight is on (also i dont feel like cutting it up)

author: Aldo22
author_rank: Super Contributor
timestamp: February 03, 2025, 09:29:15 am
content: Has anyone ever noticed that the ZT-225 is actually incorrectly labeled?It is not a 25000 counts but a 25499 counts meter.This is of course not a big plus, but it just means that the 2.5V of an AD584L voltage reference is displayed with 5 digits, even if the measurement is slightly above 2.5V.The AN870 strictly stops at 19999 and does not display e.g. 2.0000V.

author: Paul T
author_rank: Regular Contributor
timestamp: February 03, 2025, 11:10:08 am
content: Quote from: Aldo22 on February 03, 2025, 09:29:15 amI noticed the same thing with the ANENG SZ20 while compiling resistance range data. It's not limited by segments available in the screen display.I have a few meters which promise fewer counts than the capacitance range actually reports.

author: Paul T
author_rank: Regular Contributor
timestamp: February 03, 2025, 12:11:43 pm
content: @Aldo22,What is your findings with accuracy when the meter ranges to the next level of counts? I noticed at the upper level of precision on resistance there is a shift in the actual value, beyond the precision. Perhaps the high precision result at the upper end of the range is less trustworthy than the lower count result along the next range. It may also depend on the value of physical resistors if they are using any external ladder.In theory, you change the range and the extra digit gets rounded, but that seldom seems to be the case.

author: Aldo22
author_rank: Super Contributor
timestamp: February 03, 2025, 01:32:48 pm
content: Quote from: Paul T on February 03, 2025, 12:11:43 pmI'm not quite sure if I understand you correctly.Is that what you mean?2.5488VIncrease source by 1mV =2.550VThat looks right to me.What I sometimes wonder about is the difference between the VDC setting and the VDC AC+DC setting.There are some deviations in the mV range here.Well, VDC AC+DC has a different accuracy: ±(0.5%+3).I think it is within the tolerance limits.

author: Paul T
author_rank: Regular Contributor
timestamp: February 03, 2025, 11:26:10 pm
content: The range misalignment is likely more pronounced on functions which carry a larger tolerance percentage.

author: mwb1100
author_rank: Frequent Contributor
timestamp: February 04, 2025, 04:15:19 am
content: Quote from: Aldo22 on February 03, 2025, 09:29:15 amIt's not uncommon for meters to go a bit above their specified count.It's also not uncommon for them to switch ranges right when they reach the specified count.

author: Aldo22
author_rank: Super Contributor
timestamp: February 04, 2025, 09:02:49 am
content: Quote from: mwb1100 on February 04, 2025, 04:15:19 amYes, I think you can identify this by whether a DMM is labeled with x999 counts or x000 counts. Is that correct?Examples from my DMMs:AN8008: 9999 counts. No tolerance.AN870: 19999 counts. No tolerance.ZT-225: 25000 counts. Up to 25499UT123: 4000 counts. Up to 4099.

author: Aldo22
author_rank: Super Contributor
timestamp: February 04, 2025, 10:10:28 am
content: Quote from: Paul T on February 03, 2025, 11:26:10 pmI don't really see a problem here.Sure, it could round up to 2.546k, but the specification is ±(0.2%+3) for resistance.So plus or minus 3 at the last digit is allowed.

author: Paul T
author_rank: Regular Contributor
timestamp: February 04, 2025, 10:20:50 am
content: Thanks Aldo22! Hold onto your unit, it's really good. Not sure if you got a gem, or if the ZOYI is better than the ANENG. Yours works better than mine in AC+DC volts and also keeping accuracy when range switching.

author: Aldo22
author_rank: Super Contributor
timestamp: February 04, 2025, 11:11:40 am
content: Quote from: Paul T on February 04, 2025, 10:20:50 amAC measurement can be quite tricky due to the limited bandwidth.With a square wave it quickly becomes inaccurate, probably due to the slew rate?An oscilloscope is better suited for this.

author: Paul T
author_rank: Regular Contributor
timestamp: February 04, 2025, 11:16:26 am
content: I should have said DCV is more consistent on your device when measuring in the AC+DC setting, as we noted earlier in the thread.

author: Aldo22
author_rank: Super Contributor
timestamp: February 05, 2025, 09:04:02 am
content: Quote from: Paul T on February 04, 2025, 10:20:50 amI suppose you have the same HW version?

author: Paul T
author_rank: Regular Contributor
timestamp: February 05, 2025, 11:31:12 am
content: I have not unscrewed my aneng yet. Just got it a couple months ago.Darren Walker has the same version as you it appears. His review is from a year ago.https://youtu.be/W9UhA54JboA?si=QM6MkHwrGrzkodXS&t=1029

author: Paul T
author_rank: Regular Contributor
timestamp: February 05, 2025, 03:02:10 pm
content: With additional testing, it seems the manual range transition has negligible offset.Voltage was perfect across 0.025, 0.25, 2.5, 25 VDCResistance was as follows (decade resistor board)250.08 to 0.2503k2.4936k to 02.493k24.965k to 024.97k249.28k to 0.2483m

author: Aldo22
author_rank: Super Contributor
timestamp: February 05, 2025, 03:32:32 pm
content: Quote from: Paul T on February 05, 2025, 03:02:10 pmHmm, but these two values are probably out of specification of ±(0.2%+3).Are you sure this measurement is correct?

author: Paul T
author_rank: Regular Contributor
timestamp: February 05, 2025, 03:35:14 pm
content: I had a lot of texts coming in when I was typing this in!It’s a typo.

author: Aldo22
author_rank: Super Contributor
timestamp: February 05, 2025, 03:53:31 pm
content: Quote from: Paul T on February 05, 2025, 03:35:14 pmThen it looks good!Do the resistors have 1% accuracy?

author: Paul T
author_rank: Regular Contributor
timestamp: February 05, 2025, 04:48:03 pm
content: Yes it is the 8 decade resistance board from AliExpress with 1% resistors.

author: Cosmic_Starlight
author_rank: Regular Contributor
timestamp: February 06, 2025, 02:36:18 am
content: i really dont have much idea of what am doing, much less have any sort of trustworthy reference values (closest is the 1% resistors on the gm328)anyways i tried to repeat aldo's test somewhat haphazardly by putting in series 2 1k resistors, 2 240 ohms and two 47 ohms resistors and the difference between switching ranges seemed to be negligibleEDIT** holy moly the image resolution was huge for some reason sorry anyone that had to see thatalso i tried comparing measurements between the ac volts, dc volts and the ac+dc optiona brand new AA alkaline battery on dcv reads1.6238von ac+dc it reads1.6246-1.6247tried ac from mains and it seemed ac+dc read about 0.1-0.2v higher but mains is too unstable to know for surealso tried ac volts from a phone generating a 1khz sine wave audio signal from rca jacks andon acv it reads 0.1612von ac+dc it reads0.1613vi guess it makes sense ac+dc gives slightly different values since thats what the manual specifiesso idk if am good or not, coincidentally i have the exact same revision as aldo's225.v1.0.2022809.i wouldnt be surprised is there isnt any other revision