Grounding indicators are used to monitor and verify the presence of grounding systems. The purpose of a grounding indicator is to continually verify that a connection to ground is maintained in areas where potentially flammable materials are stored, handled, or transferred. If uncontrolled static discharges are allowed to occur (from people, materials, or equipment) this can lead to fires or explosions in hazardous atmospheres and result in injuries, fatalities, financial losses, and plant downtime. A good grounding monitoring system will improve the reliability of equipment and reduce the likelihood of damage as a result of lightning or fault currents.
Grounding indicators first verify a positive connection to the object to be grounded and then check for a complete "ground loop" back to a "high integrity" ground point. When the connections are in place, a light indicator will confirm the ground connection. Grounding indicators can be either battery powered or line powered. With battery powered grounding indicators, the system operates from a self-contained battery supply so that no wiring is necessary. As a result, battery operated grounding monitoring systems are portable. Other grounding indicators operate with a 110/220 volt power supply. This is generally specified when only a visual indication of ground is needed and the use of an internal battery powered supply is inconvenient.
Grounding monitoring systems are critical in protected electronic manufacturing environments, explosive, ordinance, and munitions environments. Grounding indicators can be used to verify static ground connections on a wide range of industrial plant facilities and equipment including: road tankers, railcars, barges, drums, dispensing equipment, mixing stations, totes, and other conductive equipment. The national code of practice that guides the effective control of static electricity is the National Electrical Codes (NEC) NFPA77. Although this is a voluntary standard, it has been adopted by municipalities in many states, counties, and cities as the regulation governing the electrical installations. The NEC is administered by the National Fire Protection Association and has been approved by the American National Standards Institute (ANSI). Other organizations that have set guidelines for grounding include the Underwriters Laboratories (UL), Mine Safety Health Administration (MSHA), Occupational Safety Health Administration (OSHA), and the Telecommunications Industry Standard (TIA).