A Gallagher Digital Volt Meter is recommended to have, so you know that your fence is producing the 4000KV that you need. Displays fence voltage from 100V to 10kV in 100-volt increments, as well as fence voltage from 10kV to 12kV in 1,000-volt increments. We recommend you test the voltage of your fence – you are looking for at least 4KV of output from your fences. Powered by one 9V battery with a life of 6-12 months.