Measurements of contact currents in radiofrequency fields

Radiofrequency electromagnetic fields can affect human health not only by direct interactions but indirectly through induction of charges on isolated or poorly grounded conductive (metallic) objects located in these fields. A person who touches such an object may perceive a tingling or prickling sensation or heat, or experience pain or electric shock. For sufficiently large objects, these phenomena can occur at field strengths that are relatively low and below the health protection limits based on direct interactions. We describe a method and circuitry developed to evaluate steady-state contact currents that may flow through a person touching conductive objects and give a summary of experimental tests performed. The method is simple and viable for field tests aimed at preventing pain, shock, and burn hazards in radiofrequency electromagnetic fields except those related to spark discharges. The method is applicable up to about 30 MHz.