edVirtus Reference

What Are Hazards of Electromagnetic Radiation to Equipment (HERE)?

How Can Strong RF Fields Disrupt Electronic Systems?

Hazards of electromagnetic radiation to equipment, abbreviated HERE, occur when RF electromagnetic energy couples unintentionally into electrical or electronic equipment and degrades its operation. Unlike HERP, HERE concerns system performance, reliability, and safety rather than direct biological effects.

RF energy may enter equipment through antennas, cables, wiring, apertures, connectors, conductive structures, or direct field penetration into circuits. The coupled energy can create unwanted voltages and currents that compete with the signals the equipment is intended to process.

Possible consequences include false indications, data corruption, degraded receiver performance, unintended control actions, intermittent resets, sensor errors, communication failure, or permanent component damage. In a safety-critical system, even a temporary malfunction may have serious operational consequences.

Susceptibility depends on frequency, field strength, modulation, pulse characteristics, cable length and routing, enclosure design, grounding and bonding, filtering, shielding, circuit bandwidth, and the immunity of the components involved. Resonant wiring or apertures can make particular frequencies especially effective at coupling energy.

HERE overlaps with electromagnetic compatibility and electromagnetic interference engineering. In many organizations, equipment hazards are managed under electromagnetic environmental effects or EMC programs rather than under personnel-exposure rules. The terminology may vary, but the coupling and susceptibility problem is the same.

Assessment may combine site field measurements, cable-current measurements, equipment immunity testing, radiated and conducted susceptibility tests, and analysis of the installed configuration. Testing should reproduce credible operating modes without creating unsafe or damaging conditions.

Controls include shielding enclosures, filtering power and signal lines, improving grounding and bonding, rerouting or shortening cables, increasing separation, controlling transmitter operation, using fiber-optic isolation, and selecting equipment with adequate immunity.

HERE assessment is especially important where strong transmitters operate near navigation, medical, industrial-control, aviation, maritime, communications, or protection systems. Safe operation requires both adequate transmitter control and equipment designed for its electromagnetic environment.