Nerve conduction velocity (NCV) is a test to see how fast electrical signals move through a nerve.
Patches called surface electrodes, similar to those used for ECG, are placed on the skin over nerves at various locations. Each patch gives off a very mild electrical impulse, which stimulates the nerve. The nerve's resulting electrical activity is recorded by the other electrodes. The distance between electrodes and the time it takes for electrical impulses to travel between electrodes are used to determine the speed of the nerve signals.