[General Accessories] vectron:
With probably over a hundred of gadget and accessory reviews, this is the first time I'm making such a bold statement. Yes, I do consider this as one of the MUST have tools for any smartphone users. This is Charger Doctor, USB amp-volt tester I just got from DX.com : http://dx.com/p/usb-av-usb-power-current-voltage-tester-translucent-blue-silver-235090 and this little guy is only $5.99

How many times we seen posts asking "my phone is not charging fast enough" or "I have a bunch of usb cables and old chargers, which one to use"? I lost a count. When it comes to chargers, at least those get labeled, although some are "mislabeled" or get degraded after months of use. Why do you think our phone is charging slow? Its the current output of your charger AND usb cables you are using. The charging formula is very simple, capacity of your battery in 'mAh' / rating of your charger in 'mA' = to get time in 'h' to charge. The number is usually approximated since nothing is ideal due to efficiency loses. So how do you find this perfect combo of charger and cables to give you the fastest charging speed? Use Charger Doctor!!!

This is a very simple little pass-through usb dongle. For those who know anything about electronics, and I actually took the case apart and snapped a few shots for your to appreciate the guts of it, or anybody who just have an open mind - the principle of this device is simple. You have full size usb input and output with interconnected power and signal, but power will go through a sensing resistor to measure voltage drop for calculating the current (ohm's law of V = I * R). I'm just guessing by looking at this gadget, it has some DAC to convert and to output the reading on a small led display which shows your Voltage reading and I-current reading. Here is a catch, since its full usb - it will connect between your charger and usb cable so you are NOT measuring at the output of the cable going into the phone. By using free Galaxy charging app you can approximately see the drop between the charger and going through the cable. Plus, this way you can "calibrate" the cable loss if you want to use this setup with another tablet or smartphone, other then Galaxy type.

In simple words for those who might not be following my technical explanation, just gather all your chargers and cables, and test different combinations to find the highest current reading you can get. KEEP in mind, when this little gadget is plugged in, it will draw its own current to power up dac and LED display, that is why you will see an additional drop when you compare reading with just a charger and a cable, and with this Charger Doctor in-between So once you find a perfect combo, unplug this dongle because it will "slow" down your charging by funneling some of the current. To demonstrate what I mean, I have a little presentation below with combination of 2 wall chargers and 3 pairs of cables, and took comparison pictures with Charger Doctor and without it. Keep in mind, this might not be 100% accurate, but it will give you a really good idea. As you can see, I found that one of the usb cables (black one) was the worst one, and the best combination of charging speed was using original Samsung OEM wall charger and yellow usb cable from UE boom. I hope they will also release a similar device with micro-usb in and out, but even with full size usb - for $5.99 its one cool gadget! Also, if you have solar powered charger - this will be a must where it will help you greatly to find a sweet sunny spot for a maximum current charge.

Here are the pics.

And for EE or hobby geeks: