DMM Analog Front End Chips - Page 1
Forum section: electronics / projects

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: May 29, 2025, 01:33:25 pm
content: Hi,I want to know your suggestions about DMM Analog Front End Chips, Dave have used HY3131 in their DMM, since that time I want to know what better parts are available, specially from Chinese manufacturers, I have some cool Ideas about designing a new DMM.

author: coromonadalix
author_rank: Super Contributor
timestamp: May 29, 2025, 03:39:36 pm
content: you have the Cyrustek, Fortune Semiconductor, Hycon as you postedsome githubhttps://github.com/tpwrules/121gw-re/blob/master/pdfs/DS-HY3131_EN%20-%20HY3131%20multimeter%20chipset.pdfyou had the Siglent dmm shield with the 3131, you can still grab designs or arduino codethe 121gw if i recal has the schematics floating on the web and hereand some older like maxim Max134 31k counts etc ... it depend of your designs and availabilityCyrustek ESS51966a i think goes up to 100k countsFortune ... FS9704B the 80,000 count chipFortune ... FSUP01-003 80k countsno pun but you wont re-invent the wheel ?Nowadays cost effective one are theses highly integrated ones, no special asic's, and mostly you need to have ways to calibrate with software OR without

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: May 29, 2025, 10:45:14 pm
content: QuoteSuch as?Do you have any clue about brymen BM789 chip? I want something with Rechargeable Battery and BLE and USB connectivity.

author: Terry Bites
author_rank: Super Contributor
timestamp: May 30, 2025, 03:43:46 pm
content: Cool as in no one else has already done it, tell us more.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: May 31, 2025, 07:59:15 am
content: QuoteI Just told you, with rechargeable batteries that can be charged via USB and have BLE for logging too.

author: razvan784
author_rank: Regular Contributor
timestamp: June 01, 2025, 11:24:08 am
content: A few (hopefully useful) notes:BLE connectivity is certainly a nice feature, and has already been successfully implemented in other products such as Dave's 121GW.Having an integrated battery charger is also a nice idea in principle, as it easier to plug in a USB cable than to swap batteries between the meter and a charger.However, there is a signifigant safety issue that has probably prevented this feature from becoming more common in handheld DMMs: in the simplest implementation, the USB ground would be connected to the DMM system ground, which is usually the LO/COM lead. What happens if the user connects that to a hazardous voltage?So the solution is to have a high-isolation DC/DC converter which is quite hard to get right if you want to have proper CAT ratings.

author: tunk
author_rank: Super Contributor
timestamp: June 01, 2025, 12:01:10 pm
content: The Zoyi ZT-701 has a sliding door that blocks either the charging or COM port.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 01, 2025, 12:03:35 pm
content: Also We have very nice DC-DC convertors with lots of isolation made in China

author: EEVblog
author_rank: Unknown
timestamp: June 01, 2025, 12:09:48 pm
content: Quote from: ali_asadzadeh on May 29, 2025, 10:45:14 pmThe BLE is just a commercial bluetooth module that takes serial input from the micro, it's not part of the analog front end chip.

author: EEVblog
author_rank: Unknown
timestamp: June 01, 2025, 12:14:15 pm
content: Quote from: ali_asadzadeh on May 31, 2025, 07:59:15 amThe probelm with charging via USB is the electrical isolation required. You can't just whack a USB connector or a DC jack on a multimeter for safety conpliance reasons.

author: EEVblog
author_rank: Unknown
timestamp: June 01, 2025, 12:19:54 pm
content: Dreamtech is another one, used in Zoyi/Zotek/ANENG et.al low end meters.https://www.dreamtechintl.com.cn/en/col.jsp?id=148

author: joeqsmith
author_rank: Super Contributor
timestamp: June 01, 2025, 04:00:02 pm
content: Quote from: EEVblog on June 01, 2025, 12:14:15 pmThe UNI-T UT181A contains a rechargeable battery. There is an adapter that plugs into the four banana connectors. There is a Charge position on the rotary switch. I would imagine you could do some major damage to the meter because of this. Consider that the meter is not robust anyway. Does it even matter?

author: robert.rozee
author_rank: Frequent Contributor
timestamp: June 01, 2025, 05:43:09 pm
content: Quote from: joeqsmith on June 01, 2025, 04:00:02 pman interesting idea would be a charging 'cradle' that the meter drops into; when in the cradle the banana sockets on the front of the meter would be obscured, thereby precluding charging while the meter is connected to anything. connection to the battery (for charging) could be effected by a pair oflongthin pins that extend from the cradle up into the body of the meter so the charging connections are inaccessible normally.since the Digilent DMM Shield is out of production, and the schematic readily available, why hasn't someone just cloned it as a JLCPCB project? it seems this would be the perfect basis for a number of DIY DMM projects.cheers,rob :-)https://digilent.com/reference/add-ons/dmm-shield/start

author: floobydust
author_rank: Super Contributor
timestamp: June 01, 2025, 06:06:42 pm
content: The HY3131 is 16 years old! Hycon should give it an update already lol. It's antique.It's for pairing with low cost, 8-bit clunker MCU's. The true-RMS DSP section is only good for 1.6kHz and it has other issues. One differentiating feature between DMM IC's is their true-RMS bandwidth, and AC or DC coupling.Hycon VAR is Dreamtech, offering turn-key firmware for your multimeter product. It's OK for chip-on-board and 8-bitters, as many low-end chinese DMM manufacturers are running their F/W mask ROM.They are not sold at the usual distributors, getting them involves some hoops.The Digilent board quickly vanished off the market, it had some problems.It will be interesting to see what Fluke does, they desperately need a new DMM IC with the closure of LTC and high costs I'm sure ADI is charging for 'ol parts.The 17B+ went with Fortune Semiconductor FS98O24.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 01, 2025, 06:13:43 pm
content: Quote from: robert.rozee on June 01, 2025, 05:43:09 pmThe charge adapter does cover all four connectors. That's not really the problem. It's the fact that you could have the probes connecting to the wrong pins and select the charge mode, damaging the meter.I saw someone hack one with a wireless charger.

author: floobydust
author_rank: Super Contributor
timestamp: June 01, 2025, 06:49:46 pm
content: Is wireless charging practical with a DMM?Your bulk tape eraser 60Hz upsets most of them unless there is extra shielding.But at say 500kHz (not sure of the coil size) even a few mV induced on the PCB will cause problems, and the common-mode noise is there too. Aluminum shielding is used.It would be really nice to be able to do long-term logging and not piss around with alkaline batteries.Braun electric toothbrush transformers are impedance-protected and have lots of insulation, might be another approach.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 01, 2025, 09:55:48 pm
content: Can you give an estimation of the accuracy you want to achieve and an indication of the total BOM cost?One of the problems you will run into is the availability of those IC's. There are not many shops that sell them in small quantities for a reasonable price.And the higher end DMM's tend to use separate ADC's. IC's like the LTC2400 or LTC2440 Those are also easier obtainable from multiple shops and in low quantities.I also have some interest in this area, but quite a long time ago I decided against it. First, you need a (better)DMM to calibrate it. And why do you want another complete DMM when you've already got one? Of course it's very handy to have more then one DMM, but those others don't have to be full DMM's. Actually, I find that a bit of a waste of money and other resources. To me at least, it makes much more sense to build a few more simpler gadgets. For example build a meter that's good at measuring voltages, but which can only measure voltages. Build another meter that can measure currents.This has a few advantages. When you have multiple DMM's you often have a few sitting on your desk just for long term monitoring throughout the day. And a meter that can do just one of the jobs of a full DMM is just fine for that. With two simpler meters (for example current and voltage) you can also monitor both of them at the same time. With DC, they can calculate power if they can communicate with each other (or with a PC).Also, if you want to go towards rechargeable batteries, my own preference would be to build an isolated DC-DC converter in the DMM. Small isolated DC-DC converter are quite cheap. I would also rather have a cable on the thing, then batteries that die somewhere halfway an important logging session. I nearly always prefer reliability over the convenience of wireless.

author: EEVblog
author_rank: Unknown
timestamp: June 01, 2025, 11:06:02 pm
content: Quote from: floobydust on June 01, 2025, 06:49:46 pmVery practical from the charging perspective.From the point of view of measurement disturbance for say long term testing, that would be an interesting test to try. Many meters usually have a V/m field spec.The thing is, hand held meters are not designed for long term testing, and they have hundreds of hours battery life for general use, so it doesn't make much sense to try and cater to some small market that wants that.

author: floobydust
author_rank: Super Contributor
timestamp: June 01, 2025, 11:31:36 pm
content: But then what is the use of Bluetooth, if not for long-term remote logging?I see it as a novelty so far. Fluke 233/381 used it as remote display, and Mooshimeter showed it for Tesla coil work in a Faraday cage.BT as a feature needs rechargeable batteries I think. If you have to worry about battery life and run over to it to turn it off, what a hassle?

author: joeqsmith
author_rank: Super Contributor
timestamp: June 02, 2025, 01:13:05 am
content: Quote from: floobydust on June 01, 2025, 11:31:36 pmI am not sure what people use the remote feature for or what long-term means to you, and if you plan to tie your phone up that long. I've ran tests over 24 hours using the PC. That said, I did buy one of those C-cell packs for one of my Flukes. I wonder if Brymen will offer something like that for their 78x.QuoteYes, but I wasn't thinking to use the meter during charging and thought you break the loop (have the wireless charging + shielding). Personally, I would rather they use a standard battery that I can swap. After having been burned by wanting to use the UT181A only to find the battery is dead, that's not going to happen to a meter I actually use. Charging would be a deal breaker unless I can swap the batteries out and use the meter while the other set is charging.

author: EEVblog
author_rank: Unknown
timestamp: June 02, 2025, 01:39:09 am
content: Quote from: floobydust on June 01, 2025, 11:31:36 pm1) For remote viewing when you can't watch the screen due to physical or safety requirements.2) Short term data logging (minutes to hours) is useful for a ton of stuff.

author: floobydust
author_rank: Super Contributor
timestamp: June 02, 2025, 01:39:24 am
content: Adding tech to an existing product i.e. BT to a DMM needs the use-case scenario thought out.I've been in a plant environment where you want to monitor and log something for a day or two, sampling say every minute. Portable datalogging, like when overnight charging batteries, looking for glitches, equipment temperatures etc.If Brymen had thought about it, just bolt on an SPI FRAM or SD card for local storage... but no it's on the app to do the bulk storage I guessI don't know but at some point we'll have to be clear about battery life with the 787BT, how many samples/hours are reasonable because nothing ruins a party like a dead battery.Can the Brymen app turn off (or on) the DMM? A problem with the rotary switch not turned to "off" to disconnect the input voltage though.Or if I forget it and leave things logging over a weekend I imagine the batteries will go dead.For people that don't know, safety standard like 61010 require a DMM to be "touch safe" that is no shock hazard from the buttons, rotary switch, battery, memory card etc. up to the overvoltage category. The assumption is the test leads (=DMM PCB) are at high voltage measuring something yet you can safely hold this in your hand.So the batteries, SD card, fuses etc. have to reside inside a screwed-on (tool required to open) cover. This is why replacing multimeter batteries sucks.

author: EEVblog
author_rank: Unknown
timestamp: June 02, 2025, 01:43:20 am
content: Quote from: joeqsmith on June 02, 2025, 01:13:05 amQuite possible for someone with the 3D modelling chops to design a DIY 3D print for a bigger battery compartment.The advantage of having an externally accessible battery.EDIT: I've asked Brymen if they would consider releasing the battery cover 3D file as open source. Their lawyers would likely say no just from a safety compliance perspective, but worth a shot.

author: PCB.Wiz
author_rank: Super Contributor
timestamp: June 02, 2025, 05:29:38 am
content: Quote from: ali_asadzadeh on May 29, 2025, 01:33:25 pmIt depends what specs you chase, but better performance usually comes from separate ADC and MCU.New parts you can expect to be better than older ones.The voltage reference also matters, as you chase precision, as does current consumption. It is all a trade off.eg TI has a new ADS8689W, 16-bit, 100-kSPS, one-channel, wide bandwidth SAR ADC with programmable input ranges on +5V supply, that has a good reference.,Nuvoton has a NADC24. that has good ADC but somewhat ordinary inbuilt ref.New better-end DMM's often include Frequency counters, so that's another angle needing attention.

author: David Hess
author_rank: Super Contributor
timestamp: June 02, 2025, 06:30:05 am
content: Quote from: EEVblog on June 01, 2025, 11:06:02 pmHandheld digital multimeters used to have 2000 hours of battery life from a 9V battery. Meters today seem to have around 200 hours of battery life.

author: EEVblog
author_rank: Unknown
timestamp: June 02, 2025, 07:00:38 am
content: Quote from: David Hess on June 02, 2025, 06:30:05 amI think the best Fluke meters ever got was 1000 hours?

author: Kleinstein
author_rank: Super Contributor
timestamp: June 02, 2025, 09:24:44 am
content: There was a time in the 1980s / early 90s when 2000 hour battery life was common. It is possible with some lower power variants for the ICL71xx cips, like ICL7126 or 7137. Already with a true RMS option one usually is a bit high than that.Newer meters, especially auto-ranging or true RMS tend to have a bit less battery lifetime, like 200-500 hours.With the battery leakage problem a somewhat shorter lifetime can even be good. With not so frequent / long use the battery might last for many years and may well leak well before empty. Another point is the usual auto turn off - it helps agains accidently leaving the meter on for weeks.The newer DMM chips have well more inside than just the ADC, display driver and reference. There is usually an input amplifier and quite a lot to CMOS switches for range and function switching, especially for autoranging. Many newer ones also include some sort of limited bandwidth digital RMS.The one easy feature I would like from a DMM is a battery compartment that is build so that a leaking battery would not cause much damage (beyond the battery contacts).

author: EEVblog
author_rank: Unknown
timestamp: June 02, 2025, 09:46:13 am
content: Quote from: Kleinstein on June 02, 2025, 09:24:44 amAh, you are right, the ICL7126 even boast 3000 hours in the banner specs. Reduce that for full multimeter functionality.The Fluke 70 series II is specced at 2000hrs for Alkaline and 1600hrs for zinc carbon.Fluke 70 series III is the same spec.The 70 series IV dropped that to 400 hours.

author: David Hess
author_rank: Super Contributor
timestamp: June 02, 2025, 12:18:03 pm
content: Quote from: EEVblog on June 02, 2025, 09:46:13 amMany of the Beckman meters had the same specification.Quote from: Kleinstein on June 02, 2025, 09:24:44 amBack then alkaline battery leakage was less of a problem. I do not remember ever having a 9 volt battery leak, at least externally.Quote from: Kleinstein on June 02, 2025, 09:24:44 amAutoranging meters of the past had significantly lower battery life than the manual ranging meters, and this was sometimes advertised as a reason to get a manual ranging meter. Now they all seem to have about the same low battery life.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 02, 2025, 12:22:32 pm
content: Quote from: EEVblog on June 01, 2025, 11:06:02 pmWith their mention of tape eraser, I think we are talking A/m not V/m, or free space magnetic flux density. These tests are covered under 61000-4-8.QuoteIf I need to log for extended periods I am using line powered equipment. That equipment is mostly on GPIB, which is controlled over Ethernet. It could be controlled over the air, or across the internet. With Labview, that has been trivial since revision 5.Battery life wise, the longest I measured was the free Harbor Freight meter DT833 at 1285 hours and the Fluke 17B+ at 1228. The worse was the UNI-T UT181A at 40 hours. Most of the more capable (functional wise) meters were under 200 hours.Quote from: floobydust on June 02, 2025, 01:39:24 amBeen there myself, logging for weeks. But, we have equipment specifically for that. Cost is far outside of what we are talking about with a low cost handheld meter.Quote from: floobydust on June 02, 2025, 01:39:24 amThere is no remote control of the DMMs power.Quote from: floobydust on June 02, 2025, 01:39:24 amFluke uses the 1/4 turn facets that can be opened with a coin.

author: David Hess
author_rank: Super Contributor
timestamp: June 02, 2025, 12:27:42 pm
content: My notes say that the Tektronix DMM916 series use either the Microchip TC8129 or HYCON Technology HY3130/HY3131. I do not remember why I have both listed.The Beckman RMS225 uses a Maxim chip.

author: joeqsmith
author_rank: Super Contributor
timestamp: June 02, 2025, 02:11:05 pm
content: I have a couple of sets of digital calipers that use a common coin cell. Seems like whenever I would need them the battery was dead. My solution was much like Fluke's.Want more life, add more capacity.

author: EEVblog
author_rank: Unknown
timestamp: June 03, 2025, 12:41:59 am
content: Quote from: joeqsmith on June 02, 2025, 02:11:05 pmSame here. Almost every time.

author: EEVblog
author_rank: Unknown
timestamp: June 03, 2025, 12:47:19 am
content: Quote from: David Hess on June 02, 2025, 12:27:42 pmI had forgotten about that one.1.6mA @9V isn't that great, for those playing the power consumption game.

author: EEVblog
author_rank: Unknown
timestamp: June 03, 2025, 12:48:29 am
content: I still want a modern benchtop battery powered meter shaped like the sloped front Fluke 37

author: David Hess
author_rank: Super Contributor
timestamp: June 03, 2025, 03:37:52 am
content: Quote from: EEVblog on June 03, 2025, 12:47:19 amAnd Tektronix did not list battery life in their specifications.I still have not found a handheld multimeter as good as or better than my DMM916, and I can think of improvements, but battery life has not been a consideration in this case.

author: EEVblog
author_rank: Unknown
timestamp: June 03, 2025, 11:42:30 am
content: Quote from: EEVblog on June 02, 2025, 01:43:20 amThe response I expected:Quote

author: joeqsmith
author_rank: Super Contributor
timestamp: June 03, 2025, 01:25:10 pm
content: Brymen could take the opportunity to make a new product and injection mold one.If customers do come up with a printable part, I would assume they are smart enough not to use it in a high risk environment.

author: robert.rozee
author_rank: Frequent Contributor
timestamp: June 03, 2025, 03:42:21 pm
content: Quote from: EEVblog on June 03, 2025, 12:48:29 amhi Dave,in terms of a DIY version, what degree of compromise would you be willing to accept? for instance would an upper DC voltage limit of +/-64v be acceptable? non-TRMS? or even no AC ranges at all? is resistance measurement essential?another approach is to rebuild a fluke 77 into the form-factor of a 37. this just requires moving the LCD to a daughter board, with the 77's PCB mounted to the bottom of the (37-style) case. rotary selector knob can be either mechanically coupled to the existing one or replaced with a new front-mounted multi-ganged rotary switch.recently i've been testing out using an ADS1115 (https://www.ebay.com/itm/356286232949) with a micro auto-ranging it from 1mV up to 64v DC with fixed 12.8:1 divider resistors. so far it is producing pretty usable 10,000 count results. adding an ACS712 (https://www.ebay.com/itm/166755159605) then gives you a fully isolated 5A DC current range, albeit at less usable counts. for me this achieves most of what is needed in a bench meter.cheers,rob :-)

author: EEVblog
author_rank: Unknown
timestamp: June 03, 2025, 11:12:20 pm
content: Quote from: robert.rozee on June 03, 2025, 03:42:21 pmI'm currently working on a smaller 3D printed back panel and stand for the Fluke 37 front panel.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 07, 2025, 09:09:05 pm
content: I hate to change or buy new batteries when I need a DMM, so maybe to cascaded DC-DC converts and a Li-ion battery is the game changer hear.

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: June 07, 2025, 09:40:24 pm
content: If 3000VDC isolation is not enough, It can go bigger with cascading two of themhttps://www.lcsc.com/product-detail/image/F0505S-1W_C20617254.html