Test / Notice: Micro-USB voltage and intensity detector


Some time ago, I had the opportunity to test a voltmeter with USB amperemeter, the USB Detector KW203.

This one had the advantage of integrating 2 USB ports, one for data and the other for refills. This has several diagnostic purposes: check the plug, check the external battery, check the consumption of the device that is used/recharged, and also check the cable (yes, not all cables are equal, far from it!)!

I didn't think about it at the time of the test, but this kind of indicator, besides as an information and diagnostic tool, can also be used as an optimization tool (other than by changing cables): in the case of portable solar panels, it's extremely useful! Just because you see the sun and point the solar panels in that direction doesn't mean you're at the bottom of the yield! At times, you just have to place the solar panel a bit differently so that you forget the intensity and therefore your smartphone, tablet, mp3 player or other device can recharge twice faster! I've tested it several times, and it's an undeniable asset! Sometimes, even if some of the solar panels are hidden by shade, they are more effective than if they were fully illuminated! What for? Because it depends on the angle of entry of the light rays.

Unfortunately, at the moment, I have not seen any solar panels incorporate this kind of indicator! Which is a shame!

I had noticed that the voltmeter / ampmeter with 2 USB ports KW203 has a "defect" when you plug 2 devices in USB at the same time: it shows you the total intensity that take the 2 devices, but impossible to know who takes what, and so you can very well have a device that recharges with 0.01A , which will be extremely long (as if not charging) and the other. In the end, in the long run, it comes back to the same because as soon as one has finished recharging, the intensity of the current will go into the other. But in the short term, so if the external battery is very limited in capacity or when you use solar panels (so limited radiation in time), it is interesting to know if both devices recharge at more or less the same speed, or if one gets recharges much faster than the other! And choose which device to charge first or let them recharge both at the same speed!

With the KW203, it's impossible to tell the difference, but there's another object that kind of makes that difference: the PMT025 cable that directly incorporates a voltmeter and ampmeter!


PMT025 Cable Features

  • Model PMT025
  • USB-microUSB cable
  • One metre long
  • No need for external energy sources
  • 0.05 to 5A
  • Voltage 5V
  • Margin of error of -or – 3%
  • LED indication (red)

The test

This time, it's literally a cable that integrates the voltmeter and ampmeter! What makes it possible to no longer walk with a cable is 2 in 1, unlike the other model where you had to have the voltage indicator – a cable.

The length is one meter, so it should be suitable for most uses without problem.

It's a USB-microUSB cable, so in a sense, it limits the devices, but in another sense, it's classic, so enough to use with a stride of devices: smartphone, tablets, some action cam, etc…

In terms of the characteristics of the voltmeter and the ampmeter, it is 5V and 0.05 to 5A. Compared with the other device, we can be a little disappointed: it was 3.2V to 10V and 0 to 3
A. Except that in reality, the disappointment is not so huge: as far as I know and if I'm not mistaken, everything in USB always uses 5V. Of course, this value can drop, but below, at the end of a certain threshold, it will not recharge anything! So voltage level, there are not really big differences, in this case with USB ports. On the amp
erage side, it's slightly different: you have 0.05 – 5 and 0 – 3. On the one hand, you have a larger detection margin but it starts very light later at 0.05 while on the other hand you have a direct detection, but a smaller margin. Which one is better? Well I want to say that there is not one better than the other, they are complementary: the ideal would have been 0 to 5A. The first (this cable) consumes a bit more ( 0.05A ), but allows a longer use over time (currently, as far as I know, it is 2.1A max recharge for a USB device, but with luck, it could still increase) while the s econd hardly consumes but is very limited, because 2 refills at the same time of 2.1A, it will not support!

Note that the consumption of 0.05A of this cable PMT025 is not done by the display of LEDs: if I plug in series the KW203 followed by the PMT025, itself connected to nothing at all, the KW203 will not indicate any amperage (that does not mean that it does not consume , but that its consumption is within the margin of error of the KW203) while the PMT205 will tell me the voltage it detects and an amperage of 0 (normal because it has no device plugged on), but therefore that the LEDS itself consumes virtually nothing.


So how to explain the 0.05A? I'd say it's the fusion of everything: LED consumption – loss at cable level (the cable is 1 meter long for recall, while the KW203 was only about 10cm!)


(Yes, I can count, the difference is not 0.05 but 0.04 on the image, but you have to take into account other elements like the margin of error of the 2 detectors, hidden numbers and also the refresh time of the indicated value!)

Regarding the micro-USB side, it is interesting to note that it fits perfectly to most smartphone cases, the microUSB port being raised from 1.5 to 2 mm.

The PMT205 is also not just a charging cable with built-in detector, but it can also carefree ly set a data exchange cable between a smartphone/tablet to a pc for example!


This built-in voltage sensor cable is primarily a complement to the KW203, both of which are excellent. Each has its own advantages and disadvantages.


  • 5v
  • 0.05 to 5A
  • 1m
  • USB-microUSB cable
  • Reloading and data transfer cable
  • Alternate volt/amp display


  • 3 to 10V
  • 0 to 3A
  • 10cm, requires 1 to 2 additional cables
  • 2 female USB ports, one data and one charging
  • Consumption of the 2 indistinguishable ports if used at the same time
  • View volt/ampere simultaneously


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