USB current/voltage monitor with mA resolution? - Page 1
Forum section: electronics / testgear

author: ebastler
author_rank: Super Contributor
timestamp: January 02, 2023, 11:47:27 am
content: Well, "Test Equipment" is a big word for this, but it's probably the right category... I bought one of those cheap, no-name USB dongles which measure voltage and current going to a connected device. Turns out that, while its display resolution is 10 mA, it does not detect a 50 mA current at all, which is a bit disappointing.Can anyone recommend a gadget which actually works? 1 mA resolution would be neat, but 10 mA with the ability to actually measure from 10 mA onward would be ok too. Does theUNI-T UT658Blive up to its "0 to 3.5A" spec, or are there other products which have worked well for you? Thank you!If I get a choice I would prefer a version with a small "pigtail" cable over the all-in-one dongle style, by the way. Less strain on the computer's USB connector, and does not block any adjacent ports.

author: AVGresponding
author_rank: Super Contributor
timestamp: January 02, 2023, 01:33:45 pm
content: Mine is just a cheap-as-possible Keweisi with 10mA resolution, and though it will register loads lower than 50mA, I wouldn't have much confidence in the accuracy, since it's the LSD and likely at least a count or two either way anyway.The one Big Clive uses has 1mA resolution iirc, something like this:https://www.ebay.co.uk/itm/394032196307.These also allege a 1mA resolution, but the low price would make me suspicious, might have to leverage eBay's buyer protection:https://www.ebay.co.uk/itm/255742466524.There don't seem to be many on a lead, surely you can just use a USB A extension cable though?

author: tszaboo
author_rank: Super Contributor
timestamp: January 02, 2023, 02:48:28 pm
content: I have a RUIDENG AT34 for self made USB stuff at work. It's OK, the display is small. Get a USB extender cable for it if the format bothers you. Haven't tested the accuracy as it's not really critical, measured 9mA on some stuff plugged in.

author: skander36
author_rank: Frequent Contributor
timestamp: January 02, 2023, 07:50:52 pm
content: There are a lot of USB testers that can be used for monitoring, and claim that can show uAmps.(attached)I am using a cheap USB tester that can show a 5 mA current from a RPI Pico.

author: Hawaka
author_rank: Regular Contributor
timestamp: January 02, 2023, 08:33:16 pm
content: I have an UM25C usb tester. Bought because of the extra digit and it claims 100uA resolution. Never checked it against a proper multimeter, but small variation in my circuit are display as small variation in current, so I guess it's not all that wrong. Never used the app tho.I just check the manufacturer (joy-it) and their USB-C meter claims 10uA resolution, would be interesting to see if that claim hold.Edit: corrected current resolution, thanks egonotto for noticing the typo.

author: ebastler
author_rank: Super Contributor
timestamp: January 03, 2023, 07:20:45 am
content: Thank you all for the great suggestions!I had not come across the class of "better" USB power monitors at all, with their ability to analyze USB-C power delivery modes. Now I am tempted by the FNB58 -- overkill for what I need at the moment, but the large and clean display and the rocker switch for controlling it are neat. Thanks again!

author: dophuc
author_rank: Contributor
timestamp: January 03, 2023, 10:49:18 am
content: Quote from: ebastler on January 03, 2023, 07:20:45 amAbout a year ago I gave a brief introduction to two types of USB meters, FNB48 and Shizuku. FNB58 is an upgrade of FNB48, but the function and usage are quite similar. Newer USB meters are now available, supporting the detection (and triggering) of the latest PD3.1 charging standard. You can refer to some types like WITRN C3, chargerlab power-z km003c... advertised as using 16 or 20 Bits ADC...https://www.eevblog.com/forum/testgear/compare-some-types-of-usb-meter-such-as-fnb48-azhzy-ct3-ud18/msg4077952/#msg4077952

author: AVGresponding
author_rank: Super Contributor
timestamp: January 03, 2023, 01:12:46 pm
content: Quote from: Hawaka on January 02, 2023, 08:33:16 pmNice! I searched that and found that forum member HKJ has a review and performance test of it on his website. Looks ridiculously good for the money (assuming you get a genuine one...)https://lygte-info.dk/review/USBmeter%20RD%20Tech%20USB%20Meter%20UM25C%20UK.html

author: egonotto
author_rank: Super Contributor
timestamp: January 04, 2023, 04:37:44 am
content: Hello,Current measurement resolution: 0.0001A is not 100 nA!Best regardsegonotto

author: MrAl
author_rank: Super Contributor
timestamp: January 04, 2023, 11:52:43 am
content: Ruideng works pretty well. It also shows accumulated mAHr's and mWattHrs.Dont remember the cost, under $10 USD Amazon.Been using this for some years now.You can get a 1 foot USB extension cord with it or longer if you like.It can show voltages higher than 5v so charging modes that put out 12v will show up as 12v also.The one thing i dont like about it is the button on the back is far too small, and you have to hold it in for about 6 seconds to get the previous milliampere hour reading to zero out. The reading is persistent so you have to clear it before taking a new reading, but that's only for the accumulated readings if you just need current and voltage you dont have to clear it. But that button bites.It does have an interesting mode where you can flip the display orientation upside down. That's so that if you have to have it upside down to begin with, you can flip the display and then it reads normally.I would certainly buy another one, unless i looked for one with more functions, although i dont think i would need much more. It reads current, voltage, milliampere hours, milliwatt hours, resistance, and temperature. I am pretty sure it has 1ma resolution. The rule though is that if you need 10ma resolution then go for at least half that, 5ma resolution, or 2ma even better and of course 1ma even better yet.