UM25C USB LCD Voltage Meter

UM25C USB LCD Voltage Meter

I have a couple of devices I needed to test the Amperage and voltage draw on. These devices are powered by USB or charged by USB.
The Raspberry Pi is one of those devices and I need to know the exact amperage it gives off.  This also includes the 7″ touchscreen I have.

So I did some digging on eBay and found the perfect USB Meter I needed.   The UM25C.  This version is equipped with Type-C in and out, Micro USB In, Bluetooth On/Off, and of course USB Female to Male connectors.
This device is not 100% accurate but close enough to give me the data I need.

So it took two months to get this device.  I did my unboxing and the guy who I bought it from on eBay apparently leaves his business card in every product he sends out.
I guess he really wants to repair phones.  The transparent card looks cool, but I don’t recommend it. Support your local repair businesses.

When you open the case you will see a QR-Code that will show you instructions to here:

On that site, you will see


Taking the UM25C out of the case for the first time!

At first glance, I was extremely disappointed. It looks like the LCD is all scratched and on top of it, they didn’t even bother to clean the fingerprints off.
Later I found out there is a protective film over it. So I’m happy.


Buttons and Interfaces

  • There are 4 buttons on the device.
    Two of those buttons rotate the screen and the other two are previous/next and edit.
  • The screen has:
    Measurement Main / Quick Charge Recognition / Charging Recording / Data Connection Cable / Measurement Graphing and System Parameter Settings.
  • Demo Image
  • Demo Image
  • Demo Image
  • Demo Image
  • Demo Image

Testing Devices


I was able to find out what the amp output is on a lot of my devices including a solar panel device I created some time ago.  I will be using this for future projects and videos on my Youtube channel.

It can take power from all 3 ports.
The UM24C is similar to this version UM25C except it doesn’t have Bluetooth and the UI is a bit different.

Desktop Application

Since I don’t have Bluetooth on my computer, I cannot show the Desktop app in a working state but here is a screenshot of the application anyways.

As you can see I really don’t like the Skyblue color.  I find it outdated.
It does have everything you need including temperature.  I can see this tool being used on the Raspberry Pi since the Pi has Bluetooth.  Unfortunately, there is no linux version of this tool.

Android Application


This is a really nice UI.   They should’ve made the desktop version look this good.   Unfortunately, they did not.
With both the desktop and the mobile app you can control the device and keep a reading without touching the UM25C.

This app is only for Android.  I wished it was also for IOS but that’s something that will probably never happen.


Technical Parameters

Model: UM25/UM25C
Voltage measurement range:4-24.000V Current measurement range: 0-5.0000A Capacity accumulation range: 0-99999mAh Energy accumulation range:0-99999mWh Load impedance range: 0.8Ω-9999.9Ω Temperature range:-10℃~100℃/0℉~200℉ Screen brightness setting: Levels 0-5
Voltage graphing range: 4-24.00V
Product weight:23.74g(UM25C)/19.26g (UM25)

Display screen:1.44 Inch color LCD display
Voltage measurement resolution:0.001V
Current measurement resolution: 0.0001A Voltage measurement accuracy:±(0.5‰+2digits) Current measurement accuracy:±(1‰ +4 digits) Time measurement range:0-99h59min59s Temperature measurement error:± 3℃/ ± 6℉ Delay off the screen time:0-9minutes
Current graphing range:0-5.000A
Refresh rate: 2Hz

(No packaging);54.56g(UM25C)/50.08g (UM25)( With packaging)
Quick charge recognition mode:QC2.0、QC3.0、APPLE 2.4A/2.1A/ 1A/0.5A、Android DCP、SAMSUNG


Created By HangZhou RuiDeng Technologies Co., Ltd

If you’re looking to find a device that can read the voltage I would recommend this.  I would also recommend a good Voltage meter too if you need a more precise accuracy.
If you do connect to Bluetooth just enter 1234 to pair with the device.

Do you have one?  Are you thinking on getting one?  Please let me and others know and what you will be using it for.

If you want to buy one  Amazon eBay

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