The interaction between ELF electric fields and RF survey meters: theory and experiment

An RF survey meter is often used to evaluate the safety of human exposure to RF electromagnetic fields. However, it has been noted that erroneous meter indications occur when the meters are used in strong, extremely low-frequency (ELF) electric fields, such as those found near electric power transmission and distribution facilities. In this paper, coupling between an ELF electromagnetic field and an RF survey meter has been studied theoretically and experimentally. It has been shown that coupling large enough to result in erroneous readings can be caused by unbalanced currents as small as 0.1% of the balanced currents on the transmission line that connects the probe to the readout unit. Unbalanced currents of this magnitude can be caused by capacitive coupling to the probe and readout unit.