Mitigation of RF Radiation and Electromagnetic Interference from a Lithium-Ion Battery Pack Used in Wearable Safety and Health Devices in the Mining Industry

Lithium-ion batteries are used widely to power various portable devices operated in many industries, including mining. The safety of using lithium-ion battery is, therefore, always a topic of concern. Researchers from the National Institute for Occupational Safety and Health (NIOSH) recently found that a personal dust monitor (PDM) powered by a lithium-ion battery could unintentionally produce RF radiation that electromagnetically interfered with the miner-wearable-component (MWC) of a magnetic proximity detection system (PDS) causing the MWC to function improperly. A PDM is worn by a miner to continuously monitor dust exposure. A PDS consists of its magnetic radiation antennas mounted on a mining machine to generate steady magnetic fields and an MWC that measures magnetic fields to determine if the miner is at a safe distance from the machine. If the miner is at an unsafe distance, the PDS will warn the miner or stop the machine to protect the miner from being pinned or struck. Electromagnetic interference from a PDM causes the PDS to fail to warn the miner and to stop the machine putting the miner at risk. In an effort to understand the nature of this interference, NIOSH researchers characterized RF emissions from the PDM and found that the lithium-ion battery pack was the strongest RF emission source among the internal components. NIOSH researchers also investigated different shielding materials as a mitigation strategy to reduce RF emissions and to prevent accidents potentially caused by interference with the PDS. The measurements of RF radiation from a PDM's lithium-ion battery and the results of the shielding material evaluation are presented in this paper.