Ruideng UM25C USB Colour Display Tester

You may recall I have, elsewhere in here, blogged about Ruideng power supplies.


UM25CThe Ruideng UM25C USB tester unit comes in a handy metal container without leads. There is almost no info with it but a PDF document is available online.

A snug fit in the hand, the UM25C does its job without fuss and appears well-made.


Here it is in action, charging my phone from a power supply. As it happens I just sent a phone back to China with a charging issue and it occurs to me that with this gadget I could’ve given a more accurate diagnosis of the problem.

UM25C monitoring my old HTC phone charging

The unit measures incoming/outgoing voltage and outgoing current. Keeping leads short minimise losses and of course the unit cannot measure losses on the input lead so it is particularly important to keep the latter short.


The unit has an excellent full colour display on top and selection buttons on the two long sides. The display shows temperature, voltage and current as well as charging mode when known.

Alternative screens show current and power over time in mAH and mWH. In the example here, my phone is charging at 4.956V and 0.327A

Input options include microUSB and USB C as well as standard USB. Output options include standard USB and USB C. Given the number of new devices now using USB C, this is very useful. Output voltage readings are of course at the UM25C end of the short output cable.

To make any significant use of the temperature reading, you would of course have to mount the unit right next to the battery you are charging as the unit merely shows the ambient temperature around the unit itself by default. However, being able to see charging current and power in both instantaneous form and over time is in fact very useful. It is also possible to see current output over time in chart form.

You can also get a readout of the resistive loss in the output lead, very useful. I could not begin to explain how much time I’ve wasted in the past before I started to realise the significance of using short, thick leads for charging phones and tablets. The unit will work with charge current up to 5 amps.

There is an online manual for this device, which indicates that there are both PC and  Android Apps ( which allow remote monitoring by Bluetooth on Android, USB on PC, however, when I downloaded and tested the software on my HTC M8 Smartphone, part of the bottom of the display was unavailable and screen rotation would not work, nor would page changing, I’m assuming the lack of functionality and partially obscured buttons are tied together. On an Oukitel K6000 Pro the software appears fine the first time we tried, using Bluetooth password 1234.

PC software would not connect. Software in the above link is available and generally works except for screen rotate – and XLS export works, but the App for Android does not appear in the Playstore.

As for the main on-board software, that seems fine. I did note however that although you can reset accumulated data, you can’t reset the accumulated time that goes with the data, which seems like it might be a bug.

As improvements/fixes come out this blog will likely reflect the charges.


9 thoughts on “Ruideng UM25C USB Colour Display Tester

  1. Really curious if anyone knows how to communicate with this device through the serial port. That is to say without the software itself, just with something like a serial terminal application

  2. I bought a UM24C and a UM25C for measurements.
    Both work very well on the current Android app.
    Unfortunately, the PC software does not show data
    for voltage and current via the Bluetooth serial
    port, but only a zero line (Windows 10 64-bit).
    Other functions such as turning the display will

    1. Is working perfect for me in Windows 10 Pro X64, When i get a zero data screen is because i get the wrong COM port.

  3. Mr. Scargill…

    I experimented and found the time is reset when unplugged from a power source.


  4. Thank you, Sir.

    If anybody figures out how to reset the time, please speak up and let us know?


  5. A great find and an excellent review – thanks Pete.

    I’ve ordered myself a couple. This always happens when I read your reviews…dangerous web site! I have an original 7 segment LED ‘Keweisi’ (crazy?!) USB tester and the later LCD one with the mAH counter but these are the next step up so I’ve bought one of each – the basic and the bluetooth one.

    It’s great to see that you’re well enough to continue with your valuable and well-respected work on this site/blog! Take care!

  6. Welcome Peter. I am glad to read the blog again and wish you all the best!
    Yes the tester look like useful. I have an older than this and there was a problems with USB connector. Even the USB connector at the tester are perfect the “user” USB does not, and after 1..2A there are voltage loses. But it is possible to add wires from the board. May be the best function is wireless, because of possible voltage difference between tester and computer. Best days for you Pete!

    1. There will always be voltage losses, that’s why I mentioned the need to use thick lead and keep short. The mere act of testing current will introduce a very small voltage loss, this can’t be avoided but it can be minimised. Glad you like my little write-up..

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