A Tiny USB Power Meter That's NOT Crap?
Yeah, I’m surprised too, for the $20 price tag, I’d expect at least basic functionality and for it to not, well, explode. And so far it’s done well. But this is me you’re dealing with, so I’m not about to leave it at that, I’m about to describe everything it does… and what it apparently does not.
So first off, yes, it’s basically a cheap little thing that I really only needed for one purpose and currently only use it to play around (except the two blog posts where I used it for actual science).
The thing itself consists of a USB 3 connector on the front and back, USB-C on the sides, and four micro buttons. Two are always “HELP” and “NEXT”, the other two rotate the display 90 degrees. Sometimes, holding “NEXT” or “HELP” can perform an additional operation, as detailed in the “HELP” menu. Naturally, given it’s quality, the help menu text isn’t what I’d call perfect English, but it gets the point across.
Anyways, let’s get into what it can do.
User Interface
Overview (default)
The default screen when it loads up. There’s the two big readouts, voltage and amperage, a temperature monitor in the top right, and across the bottom is the current wattage ($volts \times amps$), as well as the “equivalent load impedance”, and two counters totaling up the milliwatt-hours and milliamp-hours taken. mWh is essentially the “total power consumed”, and mAh can be used to estimate your battery’s capacity, but I’m not going to go into that right now (basic version: just charge from 0% to 100%).
There’s 10 counters for mAh and mWh, and the “GROUP” segment indicates which one is being displayed.
Charging Mode
This is the same as the previous screen, but two readouts are now taking up the bottom screen. On the left, the voltages of the data-positive and data-negative pins of a normal USB cable, not counting the extras in USB 3 or USB-C. The mode indicator is it’s best guess at what charging protocol has been negotiated. Since this is the cheaper model, it can only recognize QC2.0 and QC3.0 charging.
Charge Timer
When the amperage is over what’s set in the bottom, “REC” turns green, the clock starts running, and the mAh and mWh displays start tracking. If you really wanted to rest something’s capacity, this is the screen for it.
Line Resistance
With an appropriate fixed test load, you can use the device to check the resistance that a particular cable has. Given that I lack one of those, I can’t exactly show off how it works. But it’s there.
Voltage Graph
Both graphs show data over the last 10 seconds, and are auto-ranging. The voltage one shows… voltage over time.
Amperage Graph
Both graphs show data over the last 10 seconds, and are auto-ranging. The amperage one shows… amperage over time.
Settings
Finally, there’s three user-adjustable settings on this: the screen sleep timer, brightness, and temperature units. The screen will automatically turn off after the specified amount of minutes (or 0 to disable), to conserve screen life, and since the device is powered off the connection it’s passing through, consume less power.
Brightness is a scale of 1 to 6, and is… brightness.
Despite saying “1” here, the temperature units are just a toggle between reading °F and °C. 1 is F, 0 is C.
Examples
USB-A
Here I have it charging my 10,000 mAh Anker battery pack, using everyone’s favorite omni-connector. Pretty simple.
USB-C
It can also pass through USB-C, though note that one port is the input and one is output. They’re labeled.
It ships with a small USB-C to USB-C cable, so you can plug one end into the output and the other end into your device, and you can see the result above, using a certain CMDR’s phone (can you guess what my favorite game is?)