The Tacklife MUT01 Digital Multimeter USB Power Tester is down to $6.98 with code 2XQ9TEGR on Amazon. While sitting around $10 without the code, it usually sells for closer to $13 and has gone as high as $19. The drop to $7 is the best we've ever seen.

Ever plug something into your computer and it doesn't work right away? Wondering if it's the device you plugged in or the port itself? Maybe you're transferring data from a hard drive and it seems to be running slowly? Maybe you've bought a portable battery charger and want to make sure it's still working after not using it for a while? Grab one of Tacklife's USB testers. It's only $7 with this deal and it will be able to tell you just how well that USB port is functioning. It's especially great if you have a PC with a dozen USB ports on the back and you want to know if some are better than others.

It can store up to 10 inputs for you to access. It supports testing for QuickCharge and testing whether the voltage is too high or too low. It's powered by the device it is plugged into, so you'll never have to worry about a battery either. Users give it 4.7 stars based on 40 reviews.

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