Looks like a good tester but the little "instruction sheet" is useless. This tester has many different screens that you can cycle through, all displaying many different numbers - some you can understand but many you can't. I'm not expecting a detailed printed manual at this price point, but at least I'll provide a link to download the REALLY USEFUL documentation that explains the features on each screen. It's pretty much useless without documentation - because you're just looking at lots of colorful numbers that don't make any sense.