I received this USB Power Meter two days ago. My first reaction was the voltage meter worked correctly but the current meter did not provide correct values and mostly stayed on 0.00Amps.
I played with it some more and after a little experimentation found that you must plug the USB Power Meter into the power source before you plug any USB devices into the power meter or the current measurements are all incorrect. This is the trick to making this device work correctly.
The instructions that came with the USB Power Meter do not mention that you need to power up the USB Power Meter before connecting the load. I am assuming the most of the low reviews come from user that did not discover this.
I have been using this to monitor charging of an Estes Proto X quad copter battery from a Morphie USB battery. It does the job well.
I also tried it connected to an IPhone charger and an IPhone, and a computer and a few different USB devices. Worked well.
I did not check the calibration of the unit I received but I may do that in a few days and update my review. All of the numbers displayed seemed reasonable. The manual says +/- 1% for voltage and +/-2% for current.
The maximum current specified in the manual is 2.0Amps. This should be fine for most USB devices. I will point out the latest IPad chargers are 12 Watts (2.4Amps) so this is not the type of device you should be playing with if you do not know a little about electronics. It is not likely that you would damage the power source or the test device but you could damage the meter.
I noticed that that one of the other reviewers was trying to measure USB cables and complained that when putting the meter at the end of a long cable the cable losses prevent the meter from having high enough voltage to work correctly.
A method to work around this issue is to plug the power meter directly into the computer, plug the test cable into the power meter, and then connect a known load to the end of the cable. Measure current. Remove the cable and connect the same load directly to the Power Meter and Measure current a second time. A low resistance cable should show little difference between the two measured currents. A higher current difference represents a lower quality (higher resistance) cable. If you want the most accurate measurement use a resistor as a load or something with no active parts.
Since you know the voltage and both currents you can calculate the voltage drop in the cable or the resistance of the cable, but most users would just want to compare two cables to see what one is better. The cable the provides the lowest current drop is the better one. If you are using a cell phone as a load work quickly so that the change in battery charge does not affect your results.
For the price I paid I am happy with this meter. If I could make two changes they would be eliminate the power up issue where load has to be connected last. And second provide an internal battery so that the meter would work correctly over larger voltage ranges.
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USB 3.0 Tester Multimeter 3.7-30V 0-4A
MakerHawk-US
Very useful for evaluating chargers and monitoring charging
Reviewed in the United States on August 22, 2013
The description and technical details of this listing is very vague. I bought this purely on faith that it worked as I expected (as there were no reviews at the time) and was pleasantly relieved that it meets my expectations.If you read no further, I think this meter is great and would recommend it. I use it to test 3rd party phone chargers and cables and was surprised to find out how differently they perform.The company that makes this is Centech and their web site is here:http://www.centech.jp/Using Google Chrome, you can visit the site and use the translation feature to read it in English.Technical Details.Most of this information is from the manual which is very brief. I've attempted to upload a scan of the one useful page (the rest of the 4 page manual is warranty, saftey considerations, and liability.) It's hard to read, so here is the text of that manual (below). It appears this has a 2.00 Amp current maximum rating, 0.05 Amp minimum for a reading, and uses 0.01 Amp power, which should be fine for nearly all casual uses. All readings are from the main 5V power line (red pin 1) on USB. (The data + and data - lines are not monitored.)2.00 Amp maximum current.0.05 Amp minimum current.0.01 Amp power draw (to power the meter.)FROM THE MANUAL:SpecificationCurrent Value(A) | Error +/-2% max (+/-0.04 max for 0.1~2.00A)Voltage Vlaue(V) | Error +/-1% max (+/-0.05V at 5V)Major Components:USB connector (male USB plug)LCD DisplayMode ButtonTarget Device (female USB port)Operation:1. Please connect the USB Power Meter into the host machine. Note: At this time, no target device should be connected.2. When the Meter is ready for use it will display 0.00A3. Please connect a target device to the USB Power Meter.4. The mode of the Meter can be changed by pressing the mode button as follows. Initial mode is current (A) - Current value is displayed in real time. Voltage value in real time (V) - Voltage value is displayed in real time. Peak current mode (PA) - Maximum current the value is updated and displayed during this mode Minimum voltage mode (PV) - Minimum voltage is updated and displayed during this mode.MY REVIEW:A) Construction:The constructions is solid. A Circuit board, LCD display, USB plug, and USB port are housed in a clear plastic housing. It's solid, not flimsy, and seems that it will hold up to use. There is a single mode button on the top next the LCD display that seems like it shouldn't fail easily.B) Size: The size and shape of the unit is typical to a USB flash drive. It's relatively slim and long and should have no trouble fitting in to most USB ports or adapters.C) The modes. There are 4 modes. Real time current (Amps), real time voltage (V), peak current reading, and minimum voltage reading. Press the button to cycle through the modes. It takes 3 full seconds from the time you press the button until the LCD display shows the next mode but you can repeatedly press the button quickly to cycle through the modes. For example, 3 quick presses and wait 3 second, you'll see "PV" (peak voltage, the 4th mode) on the display.D) The display. The LCD display is a reasonable size and easy to read. The only criticism is the mode for shows "PV" (you would think peak voltage) which is really minimum voltage. It's just poorly named.E) Accuracy. This seems like it's pretty accurate. I compared it's readings with my own digital multimeter and came out with nearly identical readings.Conclusion:This is a great product. I would prefer it was a $20 instead of $30, but it is really very convenient and a heck of a lot more convenient than stripping wires and using a multimeter.I'm using this to evaluate a collection of AC wall and auto DC USB chargers and iPhone cables.The reason I got this was to determine the performance of different chargers and cables. It seemed like I was getting faster charging with some and slower charging with others and was able to confirm that. I've now tested every cable and every charger combination and was very surprised to learn how differently some perform. Now I believe I can evaluate the best ones. For what I paid for this I'll probably save a lot of money on chargers and cables in the future.There is one other competing product on Amazon right now: PortaPow USB Power Monitor / Multimeter / DC Ammeter for Solar Panels, Mains Chargers, etc which is a little cheaper. It seems as if both products do pretty much the same thing, but this one is a little more compact.UPDATE:I've now had this for about 2 months. I occasionally use it. Recently we used it where I work to troubleshoot why an iPad was charging very slowly and found that perhaps it was a damaged cable not delivering power. We were able to confirm changing chargers and cables fixed the issue.It's handy, compact, and works as expected.
Reviewed in the United States on August 22, 2013
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