Review: The UM25C USB tester with colour LCD and Bluetooth

Features

In addition to its built-in display, the tester also has a decent technical specification:
• Voltage: 4.0 to 24.0 V (± 0.5% + 2 digits). Resolution 1 mV (5 digits)
• Current: 0.0 to 5.0 A, (± 1% + 4 digits). Resolution 0.1 mA (5 digits)
• Load resistance: 0.8 to 9999.9 Ω. Resolution 0.1 Ω (5 digits)
• Power: 0.0 to 99.999 W. Resolution 1 mW (5 digits)
• Temperature: -10 ° C to + 100 ° C (± 3 ° C)
• Timer: 0:00:00 to 99:59:59 (hh: mm: ss)
• Capacity: 0 to 99999 mAh
• Energy: 0 to 99999 mWh

Also noteworthy is its compatibility with the following charging standards:

• QC 2.0
• QC 3.0
• Apple with 0.5 / 1 / 2.1 / 2.4 A charging current
• Samsung (virtually all mobile devices)
• Android DCP
   

 

 
The tester is also fitted with various USB ports: USB-A (in + out), USB-C (in + out) and Micro-USB (in). There are also four pushbuttons to select various operating modes and a tiny slider switch to enable Bluetooth connectivity. The model with a "C" suffix has this Bluetooth capability but the cheaper UM25 version does not. The Bluetooth allows you to pair it with a smartphone (Android app is available) or a PC so that you can view the display data in more detail on a mobile device or PC screen. For the latter option, there is extensive software available based on LabView.
This provides a really useful range of features for making USB energy measurements.

Construction

 

All this technology will of course not fit into a superslim case. Measuring  7.1 x 3.1 x 1.2 cm (2.75″ x  1.25″ x 0.5″) (L x W x H) and weighing in at 24 g it is quite a bit bulkier than a standard USB stick. The relatively large built-in screen takes up much of the upper surface. You can see from the photos it’s constructed using a sandwich-style assembly with two outer plates and a middle plate held together with screws at the corners. The sides are open so there is no protection against accidental coffee spills or ingress of conductive debris.

 

Along one shorter edge is a normal USB-A plug and opposite is a USB-A socket. On one of the longer sides, the input and output are in the form of USB-C sockets and two buttons for operation. Opposite there are also two white buttons, the UM25C version also has a black slide switch for Bluetooth operation and a micro-USB socket as input. A micro USB output would not be useful because there are virtually no cables with a micro USB connector at both ends. If you want to use the tester while charging an Android smartphone (usually fitted with a micro-USB socket), you plug the cable coming from the charger into the micro socket on the tester and use a second cable from the USB-A socket to charge the smartphone.

N.B. Anyone interested in making USB measurements is sure to have a drawer full of spare USB cables.