By Dr. Mercola. Do you notice you ... sand or concrete (especially when humid or wet). ... The Earth is a natural source of electrons and subtle electrical fields, ...
The test electrode (C) furthest from the electrode (X) under test, passes a current through the earth and the electrode under test, while the second test electrode (P) picks up a voltage. This voltage, measured between (X) and (P), is due to the test current and is a measure of the contact resistance (of the electrode under test) with earth.