A nerve conduction velocity test, or NCV, measures the rate of nerve conduction. During an NCV test, electrodes are placed on the skin and impulses are sent between them. Often performed in conjunction with electromyography, or EMG, an NCV test can detect nerve damage or dysfunction based on the information it gathers from the nerve impulses. It does this by measuring the time it takes for the impulse to leave one electrode and reach the other.