To easily check Body Voltage ground the Black Lead (to radiator or Earthing Product or Ground Plug) and hold the Red Lead between finger and thumb, or place on bare skin on the body. Take a reading while not earthed. You may need to adjust the AC Voltage Range by pressing the Range Button to obtain a reading.
Then test again while feet are on the Earthing Product to see how much Body Voltage has been reduced by. Using an Earthing Mat for example, you should see the AC Voltage reading drop into the low mV and to even 10ths of a mV. Can also be used to give an idea of the Resistance (therefore conductivity) of the Earthing Product. Full instructions provided. Will also measure flow of Free Electrons into the Body.