Electromagnetic Susceptibility (EMS)

Electromagnetic Susceptibility (EMS) is the ability of electronic devices to continue functioning properly when exposed to electromagnetic disturbances. In compliance terminology, EMS is referred to as immunity and is, alongside Electromagnetic Interference (EMI), the second core component of Electromagnetic Compatibility (EMC).

Types of EMS Tests

EMS is evaluated through standardized immunity tests that simulate disturbances a device may encounter in real-world environments:

• Electrostatic Discharge (ESD) – sudden discharges caused by human contact or nearby objects (EN 61000-4-2).

• Electrical Fast Transients (Burst) – rapid disturbances from switching operations (EN 61000-4-4).

• Surge – overvoltages from lightning strikes or power grid switching (EN 61000-4-5).

• Radiated RF Immunity – exposure to radio-frequency fields from transmitters (EN 61000-4-3).

• Conducted RF Immunity – disturbances introduced via cables and lines (EN 61000-4-6).

Performance is classified into criteria A–D, ranging from full functionality to temporary or permanent loss of function.

Relevance in Product Design

High susceptibility can lead to malfunctions, data corruption, or safety risks when devices are exposed to electromagnetic fields. Typical challenges include:

• Malfunction of automotive electronics due to nearby transmitters.

• Medical devices affected by mobile phones or hospital equipment.

• Industrial control systems disrupted by switching operations or surges.

To reduce susceptibility, design measures such as shielding, filtering, proper PCB layout, and grounding are applied during development.

Testing and Standards

EMS compliance is verified in accredited laboratories using signal generators, coupling/decoupling networks, and anechoic chambers.

Relevant standards include:

• EN 55035 (CISPR 35) – immunity for multimedia equipment

• EN 61000-6-2 – immunity for industrial environments

• EN 61000-4 series – test methods for ESD, Burst, Surge, RF immunity

• IEC 60601-1-2 – medical device EMC requirements

These standards define test setups, severity levels, and performance criteria to ensure reliable device operation in disturbed environments.

Practical Relevance

Demonstrating immunity is essential for EMC compliance and market access. Manufacturers must show that products meet immunity requirements in line with international standards.

→ See also: Electromagnetic Compatibility (EMC) and Electromagnetic Interference (EMI).