Test/Review of Xtar VI01 USB Current/voltage detector

EDC Gear for Flashlight Carriers USB Power Devices
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Xtar VI01 USB Current/voltage detector





Xtar has made many flashlights and good chargers, this is a new type of product from them. It is a current and voltage meter to use in a usb connection.



I got the device in a cardboard/plastic package. It was very easy to open, the cardboard could slide out. The only contents in the package is the device, no usb cable or instruction sheet and it is not needed.



There is an usb connector in each end, one male, one female.



One of the usb connections has a loose cover. I like having a cover over the usb connector, but I do not like loose parts.



Here it is plugged into a laptop and connected to my phone. The display will show 3 digits and a letter, A for ampere and U for volt. The decimal place is always fixed giving the display a resolution of 0.01 volt and 0.01 ampere.



Another test with my laptop, this time with two different cables.
When using the two wire cable the phone will only charge with low current. Using the 4 wire cable (with data), the phone can charge at much higher current.



Some other tests it can be used for.



Measurements



To measure I needed some connection with very low resistance. I made two usb connecter with fairly thick wires sticking out.



First I measured the two when connected together, the result was 0.03 ohm or 30mOhm, for the wires and connection between the two.
Because I do not know how this is distributed, I cannot compensate for it in the voltage measurements. Anyway, these looses will also be present when using it in real situations and usual they will be larger.



With the device connected.



The actual setup required two high precision DMM's, one to measure input voltage and one to measure output voltage and a electronic load.
Voltage was measured on the wires sticking out of my test usb connectors, to avoid voltage drops in thin usb wires.



About are some of my measurements. In the two red lines I am way outside the rated specifications and the display shows wrong values.

With a few more test I could draw some conclusions:

  • Volt was within +/- 0.01 on the display when not loaded.
  • Ampere is within +/- 0.02 on the display.
  • When loaded with 2.5A the displayed voltage is about 0.1 volt to low.
  • When loaded the voltage will drop, calculations shows the device has between 0.16 and 0.17 ohm resistance, this includes the measurement resistor, the internal connections and connections resistance (The 0.03 ohm from above is subtracted).
  • The voltage is shown for the input voltage, i.e. the voltage on the usb output that supplies the current to the device.
  • When voltage drops below 4 volt the precision will be reduced (The device is only supposed to work down to 4.5 volt).
  • The voltage readout is usable down to about 3 volt.
  • The device uses 0.025A (25mA) from the usb power, this current is not included in the display reading
  • The usb data lines are passed through, this means the coding on a usb output will be seen on the connected device.





After a short time the measurement resistor in the device gets warm.



Running 1 hour at 2.5A made it warmer (max. temperature is higher, see scale) and the current readout was still correct.



Conclusion

The device works as expected and can be very useful to check all types of usb devices with.
The voltage readout will be precise at small loads (i.e. below 1A), but at the higher current it will show a slightly low a value. The current readout is always precise.



Notes

The device was supplied by Xtar a review.

2

That is a really fun gadget, never seen it before. I want it, I mean, I really need it ;-)

Thanks for testing, I am curious about the retail price.

3

Darn, you beat me to it :stuck_out_tongue:
Anyway thanks for the review, i just got mine today.

4

5-6€ in europe, maybe a bit cheaper on ebay.

5

You don't have a USB Charger Doctor do you? I tried using mine to test my solar charger and the display was almost impossible to read even when I tried shading it.

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I’m curious about the accuracy compared to a typical Charger Doctor. Do you have one to make such comparisons?

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Oh, I see in that thread that HKJ does have the Charger Doctor, an older version though.

8

HkJ or anyone else that might be familiar with this device, I picked up one of these Xtar USB meters and I’m finding the current to read about 0.02A too low. I have a breakout box for USB and so I had my Fluke 87 in series measuring the current. The fluke was also on the load side of the USB connection and not on the USB power source side. At no load I read 0.00A at the Xtar along with reading 0.000A at the Fluke…………so its not displaying the quiescent current to operate the USB meter. At first I was thinking it was off because it was measuring the quiescent current, but that would make it read 0.02A too high. So the conclusion that I’ve come up with is that its just flat out off and low by about 0.02A. The error seems to be constant on up the amperage range. That tells me its an offset problem, yet at 0 amps, that’s what it reads. The moment there is even a little current its reading low and off by 0.02. Probably not much can be done with it since it doesn’t look to be a gain issue where the possibility of adjusting the current sense resistor would come into play.

But wondering if you have any advice on this…………or just live with the inaccuracy knowing in my mind which way I need to fudge the output. (ie: add 0.02A to everything I see).

I’m mostly interested in these to measure USB current. The voltage was pretty spot on for 2 digit accuracy. (ie: Xtar=5.15, Fluke says 5.145v)

In comparison, I also have an YZX Studio USB meter which is almost dead on with the amperage accuracy of the Fluke……….and that was out to 3 to 4 decimal point accuracy…………very impressed!