How is this device different from a simple galvanometer?
Inside the E-meter device, there are some transistors, and many resistors, and that makes the device a little more complicated then the simple galvanometer. The movement of the E-meter scale is designed to bounce around a lot, it is intentionally made unstable to produce extra data for the auditor to interpret. Without the trained interpreter, the data from the E-meter device is useless. Just as the disclaimer on the device says: "By itself, this meter does nothing.''