EEVblog 1693 - Uni-T UTE310 Power Meter Teardown & Practical Demo - Page 1
Forum section: electronics / general

author: EEVblog
author_rank: Unknown
timestamp: June 30, 2025, 01:26:43 am
content: A teardown of the Uni-T UTE 310 Digital Power Meter, and an example meausing the power consumption of the new Brymen BM786BT multimeter in bluetooth data transmission mode.https://uni-trendus.com/products/ute310-digital-power-meter00:00 - Uni-T UTE310 Power Meter02:44 - Teardown06:54 - Power supply07:47 - FPGA and ARM processors (plural)09:23- Seperate isolated volatge and current measurements11:28 - Special Snowflake shunt resistor14:04 - Turn on and a looks at the current ranges15:04 - Flashing LEDs15:51 - Shunt resistor heatsink sizing16:46 - Inside the metal cans. ADC's + Amplifiers. Talking head Dave, PCB walkthrough27:05 - Power on, offset error, and the tyranny of ranging30:19 - Demonstration with BM786BT multimeter battery consumption34:51 - Current waveform view39:11 - The offset has drifted40:43 - Conclusion

author: Kleinstein
author_rank: Super Contributor
timestamp: June 30, 2025, 06:56:32 am
content: The OPA1656 is a high quality OP-amp, but not so much an Audiofool one, but a surprisingly cheap ($2,50 range Qty1 ) high grade dual OP-amp.Those matches resistors are very likely Susumu RM series ones.The LT1037 is a slightly improved OP37, which is the decompensated OP27 variant. The point is low noise and good bandwidth.Chopper OP-amps are slower and usually add some noise at there internal chopper frequency, which is maybe in the 100-300 kHz range. So not such a good combination with a fast ADC.If they would want better accuracy the obvious way would be more shunts and smaller steps.

author: tszaboo
author_rank: Super Contributor
timestamp: June 30, 2025, 10:12:20 pm
content: Quote from: Kleinstein on June 30, 2025, 06:56:32 amI'm a bit surprised to see those audio opamps in a circuit where DC accuracy, stability and offset is probably more important. I would have expected some OPA350 or similar parts. Driving those Linear ADCs is not trivial, large bandwidth is needed because they present a switched capacitive load. And the driver needs to settle within 0.5 LSB within less than a microsecond.I never understood why these meters don't come with regular power socket output.Something else I noticed, that the FPGA and the micro both seem to be connected to that SRAM. I wonder if they use the memory interface to communicate with each other, like the FPGA just appears as memory space for the micro.While originally the design looks clean, I think it's actually quite all over the place. Like there are all these isolation slots in some places, but you have tracks that are the same distance and those don't have that. Also the metal can violates those distances, and the resistor divider doesn't have isolation. And a singe current shunt? Busbars for only 20A?

author: Martin72
author_rank: Super Contributor
timestamp: June 30, 2025, 10:36:27 pm
content: Nice device, I hope there will be a proper review at some point.Regarding the “offset drift” mentioned:This device will also need some time to stabilize thermally, so there's no need to be surprised.

author: MaxPi
author_rank: Newbie
timestamp: July 01, 2025, 02:06:26 am
content: U57 is a little crookedly soldered

author: Kleinstein
author_rank: Super Contributor
timestamp: July 01, 2025, 06:38:30 am
content: From the drift specs the OPA1656 is actually better than the OPA350.The OPA350 is shown in quite some ADC examples, but the specs for drift and low frequency noise are relatively poor.The OPA1656 is labeled an audio amplifier, but it still a DC specs that are not that bad. Only the offest voltage itself is relatively high. < 1 mV is still good for audio.For the ADC driver settling to 0.5 LSB between the samples is the ideal case, but for the high speed, high resolution this is more wishful thinking. With a constant sampling rate one can get away with less.

author: tszaboo
author_rank: Super Contributor
timestamp: July 01, 2025, 08:53:12 am
content: Quote from: Kleinstein on July 01, 2025, 06:38:30 amYeah, the OPA350 is quite a dated part, that I used about a decade ago to drive similar ADCs. With offset compensation, similar as bench multimeters do.Today there are some e-trim OPAs that will be better AC specification. It's just surprising to see an Audio OPA in that circuit. But when I look at the datasheet, the DC spec is there, and it's likely cheaper than the more precision focused parts. If I would need to select a part today, I would've picked OPA328 for example.The fast settling isn't that impossible. The ADC driver will have a small RC filter on the output, like 10 Ohm 1nF or something like that. When the sampling capacitor is connected, which is the order of pFs, most of the charge is coming from the 1nF. The OPA need to be fast to charge up this resulting load to 1/2 LSB in a relatively larger time.The annoying part is that you can design the driver circuit and test it, but never actually measure it. Your 8 or 12 bit scope doesn't have the chance to see the voltage drops, not dynamically. Especially not if you have any multiplexing the system.

author: Martin72
author_rank: Super Contributor
timestamp: July 02, 2025, 12:12:05 pm
content: Quote from: MaxPi on July 01, 2025, 02:06:26 amIf that's a picture from Dave's video, then I would take a closer look at the IC if I were him.As it looks now, one side isn't soldered at all and is just lying on the pads, or there is still solder paste between pins 9 and 10:

author: thm_w
author_rank: Super Contributor
timestamp: July 02, 2025, 08:25:15 pm
content: Quote from: tszaboo on June 30, 2025, 10:12:20 pmIts two current shunts right? There was a relay click.Busbar design would be shared with the UTE310H which does 50A.Quote from: Martin72 on July 02, 2025, 12:12:05 pmU57 = LTGVR =LT8609Vin is connected to EN, probably as intended.

author: Martin72
author_rank: Super Contributor
timestamp: July 02, 2025, 08:46:56 pm
content: Hi,QuoteYes, but that's not what I meant.If that's still solder paste, it's a sign that the side of the IC hasn't been soldered.If Dave could take a detailed picture of it, that would clear things up.

author: EEVblog
author_rank: Unknown
timestamp: July 03, 2025, 11:47:09 am
content: Quote from: MaxPi on July 01, 2025, 02:06:26 amFrom my hires photosLooks crooked but ok.The unit wouldn't work if this wasn't electrically ok, it generates multiple voltage rails for all the FPGA and ARM logic.

author: Martin72
author_rank: Super Contributor
timestamp: July 03, 2025, 12:12:25 pm
content: These solder joints......would never get through our QC, it's also a question of reliability.But hey, at least the device doesn't cost much.

author: tszaboo
author_rank: Super Contributor
timestamp: July 03, 2025, 12:27:37 pm
content: Quote from: thm_w on July 02, 2025, 08:25:15 pmMaybe? I've seen one shunt that looked like a PBV shunt. The other is probably something very different.

author: pdenisowski
author_rank: Super Contributor
timestamp: July 05, 2025, 08:49:34 am
content: Very cool review - thanks!And with regards to why "U" is used for voltage: the notion that "U" comes from the German word "Unterschied" seems to be the result of Google's AI having been trained on a few random English-language internet posts. If you ask Google this question in German ("Woher kommt U für Spannung?") you get the answer that "U" is from the Latin word "urgere". So it appears that linguistic / etymological "truth" (as per Google) depends on which language you ask the question in

author: Furna
author_rank: Frequent Contributor
timestamp: July 05, 2025, 09:33:28 am
content: Quote from: Martin72 on July 03, 2025, 12:12:25 pmIt's over 1500 bucks ... it is not exactly on the low end product line.UNI-T is trying to acuire their space in a higher level market, but this kind of mistakes are hardly tollerated.

author: EEVblog
author_rank: Unknown
timestamp: July 05, 2025, 11:21:18 am
content: Quote from: Furna on July 05, 2025, 09:33:28 amRelative I guess. Is there a cheaper digital power meter with this capability?

author: EEVblog
author_rank: Unknown
timestamp: July 05, 2025, 11:24:29 am
content: Quote from: pdenisowski on July 05, 2025, 08:49:34 amI refuse to conceed any ground to the U afficionardoes.

author: Furna
author_rank: Frequent Contributor
timestamp: July 05, 2025, 11:45:43 am
content: Quote from: EEVblog on July 05, 2025, 11:21:18 amNone that I am aware of; but there are with (much) less capabilities from reputable vendors that cost 1/3.I am following your reviews on UNI-T devices and I am happy a new vendor is entering the market I am interested in.Anyway if I receive a device with that issue (I understand the divce is working but IMHO a component soldered that way is an issue), I wouldn't know what to do.Fix it? and discuss with UNI-T in case I need a warranty intervention later?Live with it?What did you do? Did you fix it?In any case: thank you for the review.And ... I agree with your position regarding the U

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 05, 2025, 11:50:39 am
content: Quote from: EEVblog on July 03, 2025, 11:47:09 amDefinitely not OK! Apparently it works at the moment, or else it would have been cought in the factory, but it's pretty clear that the solder has not flowed properly because of the moved IC. So this is still a reliability issue. It's also a strong indicator they do not use AOI during production, which is also quite unexpected.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: July 05, 2025, 12:00:10 pm
content: I clicked on the link to uni trendus that Dave posted here, and I got a grey window with some lottery thing and they wanted me to enter my e-mail address. So that was an instant close again for that website.

author: Martin72
author_rank: Super Contributor
timestamp: July 05, 2025, 01:38:44 pm
content: QuoteThere is an “X” in the upper right corner of the grey window....QuoteNot with 300 kHz bandwidth.GW Instek GPM-8310 comes close in terms of features, costs about the same, and has 100 kHz bandwidth.QuoteMywas also meant to be ironic.At that price, you would expect more attention to detail in terms of quality even from a Chinese manufacturer.

author: pdeal
author_rank: Contributor
timestamp: July 06, 2025, 11:26:39 am
content: Well Dave you pushed me over the top. I just bought a Hioki 3332. While the price of this Uni-T instrument is probably good for a serious user, it’s beyond what i can justify. The Hioki i found on ebay for $175. I still haven’t received it but I’m anxious to look inside it. I suspect it’s a lot more analog circuitry than the Uni-t. Good review, i enjoyed it. I think this type instrument really shines in particular with AC measurements. The Hioki is rated at 50A though. And i agree with you on the ‘U’ rubbish!

author: EEVblog
author_rank: Unknown
timestamp: July 06, 2025, 11:57:14 am
content: Quote from: Doctorandus_P on July 05, 2025, 11:50:39 amIt is hard to tell the reliability of solder joint from photos like this. Lighting alone can make a good joint like like crap, and vice-versa.

author: EEVblog
author_rank: Unknown
timestamp: July 06, 2025, 11:59:03 am
content: Quote from: Doctorandus_P on July 05, 2025, 12:00:10 pmJust close the window.This is the official Uni-T US website. They now have an entire US division and sell direct.

author: temperance
author_rank: Super Contributor
timestamp: July 06, 2025, 12:39:51 pm
content: Are we really going to shame or ditch a brand because one IC is not properly placed? Sometimes pick and place machines fuck up (for many reasons), and the optical inspection probably caught this. The IC is slightly rotated but solder joints are fine. Throw the equipment out of a second floor window three times and the IC will not come off at all. There are no shorts and the part is operating. Or do you prefer a board with flux residues and a hand placed components?A storm in a teacup.

author: EEVblog
author_rank: Unknown
timestamp: July 08, 2025, 07:12:33 am
content: Quote from: temperance on July 06, 2025, 12:39:51 pmDidn't Keysight once ship a whole batch of multimeters with dodgy soldering or something?

author: Furna
author_rank: Frequent Contributor
timestamp: July 09, 2025, 07:20:43 am
content: Quote from: EEVblog on July 08, 2025, 07:12:33 amI do not know; probably yes.How Keysight reacted? Did they recall the meters? Did they offer some sort of "repair" for free?Did you contacted UNI-T? How they reacted?

author: Kleinstein
author_rank: Super Contributor
timestamp: July 09, 2025, 10:41:38 am
content: The chip is a bit rotated, but the connections are still OK. It does not look good, but I see no issue. The optical inspection may have considered this still good enough (for Australia).