1. A sensor for sensing the contact level of a human body comprising: a first capacitor having one end connected to ground; a second capacitor connected in series with said first capacitor and defining a node therebetween; a charging element, for delivering a charge to said first capacitor; a sensing point connected in series with said second capacitor, said sensing point being capable of defining a resistance when in contact with a human resistive element; and an output device for detecting when the voltage at said node falls below a pre-defined threshold value as the result of the leakage of said charge from said first capacitor to said second capacitor.