In this surprising video I look at three USB voltage and current meters (some do additional features calculated from the measured voltage and current) and investigate their accuracy for both voltage and current compared to a decent multimeter. Are they all the same as each other (for good or bad) or are some better than others. I do a full analysis of voltage and current by altering the load going through the meters. This is done by using an Arduino to switch on (and off) multiple LEDs on a 256 LED Matrix. I then compare this to what a multimeter measures, with this being accomplished by cutting into a USB cable and intercepting a power wire so I could measure the current. The results are interesting!