1.5.2 Hazards To Equipment (HERE)
HERE results when RF electromagnetic fields induce unwanted voltages or currents in cables, electronic circuits, sensors, control systems, or other electrically conductive components. These induced signals may interfere with the normal operation of electronic equipment, resulting in degraded performance, false indications, intermittent malfunction, corruption of data, unexpected system behavior, or, in extreme cases, permanent damage to sensitive components. The likelihood of such effects depends upon the strength and frequency of the RF field, the susceptibility of the equipment, and the manner in which the electromagnetic energy couples into the system.
Modern electronic systems frequently contain high-speed digital circuits, microprocessors, analog sensors, and communication interfaces that operate using relatively small electrical signals. These circuits may be susceptible to external electromagnetic fields if adequate protection is not provided. RF energy can enter equipment directly through its enclosure or indirectly through cables, antennas, power supplies, or other conductive paths, where it may disrupt normal operation. In safety-critical systems, even temporary interference may have significant operational consequences.
Examples of equipment potentially affected by HERE include communications systems, navigation equipment, radar receivers, industrial control systems, medical devices, aircraft avionics, scientific instruments, and computer networks. Interference may cause a radio receiver to become desensitized, a navigation system to produce erroneous information, an industrial controller to malfunction, or a medical device to operate incorrectly. For this reason, electronic equipment intended for use in strong electromagnetic environments is designed to operate reliably in the presence of RF fields.
The discipline of electromagnetic compatibility (EMC) addresses many of these issues by ensuring that electronic equipment operates correctly in its intended electromagnetic environment while minimizing interference with other equipment. EMC engineering employs techniques such as shielding, filtering, grounding, careful cable routing, circuit design, and enclosure design to reduce both the susceptibility of equipment to external RF fields and the electromagnetic emissions generated by the equipment itself.
Although HERE is principally an equipment performance issue rather than a direct human health hazard, reliable operation of electronic systems is often essential for safety. Consequently, the management of electromagnetic interference forms an important part of the design, installation, testing, and operation of modern communications, industrial, medical, transportation, and defense systems. Understanding HERE therefore complements the study of personnel protection by ensuring that both people and the equipment upon which they depend continue to operate safely and reliably.