How to measure the power consumption of usb devices?

[eeguy]

Hello, I want to compare different usb devices to see which one consumes the least power. What is the recommended measurement device to use?

[JustMeHere]

Google "usb doctor"  Pick one that meets your needs

[eeguy]

It seems that there are many products named "USB Charger Doctor" but by different companies? Are these the ones you suggested? Which brand is good?

Also, are the readings instantaneous ones? It seems that the numbers will just be changing all the time.
I would prefer something that could measure the power consumption over a period of time determined by me.

[brucehoult]

The one I have ("X-Dragon") just shows instantaneous use. There is no reason they could not integrate the current / power over time and provide a UI to show that, in a similar way to "Kill A Watt" and clones do for mains electricity.

I don't know of any off-hand.

[Veteran68]

Just grab one of the myriad USB testers available these days. The market is full of them.

I currently have these:

X-Dragon - First one I owned, cheap and simple. One of my dogs somehow got hold of it and took it outside, I found it in the backyard wet and covered in mud. Cleaned it up and it still worked!

Klein Tools ET920 - The one I've used the most to this point. More sophisticated than the X-Dragon but much less than the Fnirsi FNB58. I like how it has flexible cable leads for both USB-A and USB-C, unlike the unibody testers with a rigid connector, and which require patch cables to use both A and C type connectors. The cable attachment makes it less likely to be bumped or jerked and risk breaking a port or connector.

Fnirsi FNB58 (Bluetooth) - Most sophisticated one I own, it has tons of features including waveform display of voltage and noise signals, like a mini oscilloscope. I haven't used this one as much yet as I just got it a couple months ago. Requires a patch cable to use with USB-C devices. Fnirsi does make the C1 model that has a USB-C connector, but less features.

[Rick Law]

It seems that there are many products named "USB Charger Doctor" but by different companies? Are these the ones you suggested? Which brand is good?

Also, are the readings instantaneous ones? It seems that the numbers will just be changing all the time.
I would prefer something that could measure the power consumption over a period of time determined by me.

Buying low price device like this is typically a crap-shoot.  Luckily, these are very simple and cheap device so you are not gambling big.

I have killed a few, but I still have two surviving kinds, for now I will call it type-A and type-B.  The few significant different I found are:
(1) Some may have two out port, so you can use it as a splitter and charge two things at once -- current shown is the combined.  (Type A)
(2) Some may have Watt and track the total watts used thus far and time connected.  (Type B)
(3) Some have "doubled sided" plug.  You can rotate the USB-tester 180 degrees and the testor can plug into the same socket with a different side being top-side so you can always keep the display side face up. (Type B).

Using an Adafruit INA219 module as yard-stick (connected on the source output side of the USB-tester), both (type-A and type-b) about 5% with voltage, 10% accuracy with current.  Good enough as "USB tester" but not good enough to use it for serious work.  Resolution is 0.01V and 0.01A.  The type-B (more feature filled one) appears a bit more accurate but hardly enough to matter.  The bigger issue is the voltage drop.  Type-B with the 0.1ohm shunt has a bigger drop.  It does matter because on occasion (depending on what I use as power source), the drop is enough to affect the charge-receiving device to dial down the current draw.

Bottom line, suggestion is, get one with the feature/price you need, test it out...

EDIT:  Corrected an error.  The INA219 is the source to the charge device.  It is on the OUTPUT side of the USB tester  between the usb tester and the device being charge.  I mistakenly said it was on the source side of the USB tester.

[JimKnopf]

I got some USB meters that can measure current. Best one i can recommend is the AVHzY CT-3. It can draw a graph and you can connect to it via Software and save readings. But as others pointed out, all these USB Meters are not accurate because the use the same source for powering the device itself and the DUT. But just for comparison of several devices it will be sufficient. If you want high precision measurements put a 5 or more digit Multimeter in series with your DUT. I use a Keithley DMM 6500 for that.

[LinuxHata]

Almost all are good, but all of them inject current measuring resistor into the GND line, so if you have other devices connected to same supply (computer), you will be getting not so good results

From the cheap models, I'd suggest KEWEISI brand - they are all reasonably well made and precise.
If you want top notch device with scope, logging, triggering - Fnirsi FNB48/58 are your choice.

Also consider that certain brands of phones (Oppo, Realme, Vivo, etc.) use special type USB socket - it has additional pin for charger control. Cheap USB meters have no support for that pin. Fnirsi and expensive ones - have. it is easy to identify such device - just check description, if there's support for VOOC - then you got correct meter.

[ledtester]

... But as others pointed out, all these USB Meters are not accurate because the use the same source for powering the device itself and the DUT. ...

Some USB power meters may be externally powered -- the TC66 comes to mind.

If the USB power source is stable (i.e. not a battery) I think the voltage and current measurements are accurate -- that is, the tester only displays the current consumed by the downstream device. For measuring battery capacity you definitely want to power the tester with a separate supply.

Here's a video on using the TC66 as a 5.5-digit DC multimeter:

Using the TC66 USB tester as a $30 5½ digit precision multi-meter -- TheHWCave
https://youtu.be/iZ5JjA6DoZg

Update: Here's the video where the accuracy of of the TC66 is discussed:

Ruideng TC66 / TC66C USB Type-C Tester - Way too good for just USB! - TheHWcave
https://youtu.be/rOlhibDUJgs

[LinuxHata]

Some of FNIRSI devices also have separate USB for powering.

[BILLPOD]

UM24/UM24C USB Meter - Voltage, Power and Current Tester ...