Review on Functional Multimeter Capacity Temperature Detector by Cornelius Reeves

Seems pretty accurate. The fine print is difficult to read, but it is clear enough to use a small magnifying glass. Just hold down the button and the language will change to English and volts and amperes will become a readable font size. I've tried both USB A and C but I don't have a real C device right now. Both worked fine. I will update this if anything changes. Always remember that most USB-A cables longer than 3 feet will NOT charge your device at full power. If you're not careful to buy larger cables, this is all you get. The shorter the cable, the faster it charges. In the cable, the voltage drops by 25% up to the phone, and therefore the current also drops by the same percentage, so the actual power delivered (volts x amps) drops drastically. A USB-C power adapter works much better with a USB-C device since it starts at 20V instead of 5V. Don't blame the USB-A power adapter, it's regulated at 5V. If you simply connect this tester to a power supply with no load connected, you will see that the power supply is regulating properly. Then connect the load. The voltage will typically drop a few 1/10 volts and current (amps) will flow. The tester measures actual current (amps). But voltage is measured at the point on the cord where it is plugged in, not at the phone or other device. It crashes when it hits the device.