ESD per IEC 61000-4-2: method and test levels

Author Hugues Orgitello Last updated 27 May 2026 ~14 min read

Guide · EMC immunity

Electrostatic discharge immunity testing per IEC 61000-4-2 is one of the most cross-referenced horizontal EMC tests: EN 55035 (multimedia), EN 60601-1-2 (medical), EN 61000-6-1 and 6-2 (generic), plus the full set of industrial, railway and building product standards rely on it. The test simulates the transient current produced by an electrostatically charged operator touching the equipment. This page lays out the standards framework (Edition 2.0:2008 plus Amendment 1 from 2017), the comparison of ESD models (component HBM vs the 61000-4-2 product simulator), contact and air severity levels, the test hardware, the A, B, C performance criteria, the link to ISO 10605 for automotive and IEC 60601-1-2 for medical, and the most frequent campaign-preparation pitfalls.

The ESD phenomenon and why it is tested

An electrostatic discharge is a sudden charge transfer between two objects at different electric potentials. An operator walking on synthetic flooring typically accumulates 4 to 15 kV by triboelectric effect, depending on ambient humidity and the floor material. When this operator touches a metallic appliance, the potential equalises within a few nanoseconds, with a peak current that exceeds ten amps.

The risk to the equipment is twofold. The current radiates a broadband electromagnetic field (continuous up to about 1 GHz), which couples to PCB traces and internal cabling. And if the return path to ground is poorly defined, the current flows through the electronics and can destroy a transistor junction or flip a logic register. IEC 61000-4-2 aims to verify that a product placed in a realistic environment survives such events without permanent degradation, and ideally without temporary loss of function.

Why a standardised test rather than a field test

Natural discharges vary in amplitude, rise time, and return path. To compare products between themselves and across labs, a reproducible reference signal is needed. IEC 61000-4-2 specifies a discharge gun equipped with a 150 pF / 330 ohm RC network: 150 pF approximates the capacitance of the human body relative to ground, 330 ohm reproduces the average impedance of an outstretched arm in contact with a conductive surface. The resulting current has a 0.7 to 1 ns rise time, a peak of around 7.5 A at 4 kV contact, and an exponential tail with a time constant near 50 ns.

This waveform is neither the worst nor the most common one in the field, but it is repeatable and accepted by every product standard that references ESD immunity. See CE tests for the general EMC framework in the EU.

ESD models: why several coexist

A frequent confusion concerns the different ESD models used in industry. Three families coexist, each with its own test subject and equipment.

HBM, MM and CDM: component level

The HBM (Human Body Model, ANSI/ESDA/JEDEC JS-001) evaluates the robustness of bare silicon during component-level qualification. Network 100 pF / 1.5 k ohm, peak current around 1.3 A at 2 kV. Common classes range from 0A (250 V) to 3B (8 kV); a mass-market microcontroller is typically qualified 2 kV HBM. The MM (Machine Model, ESDA STM5.2, withdrawn 2018) simulated discharge from a charged tool. The CDM (Charged Device Model, ANSI/ESDA/JEDEC JS-002) simulates a charged component itself touching a ground reference. All three apply to silicon, not to a finished product.

IEC 61000-4-2, finished product

IEC 61000-4-2 evaluates the complete product under power in its operational configuration. Its 150 pF / 330 ohm network and peak current of about 7.5 A at 4 kV are not equivalent to the component models. A product passing level 4 (8 kV contact) tells you nothing about the HBM qualification of its components, and conversely an HBM 2 kV component can survive in a level 4 product if the PCB and enclosure redirect the ESD current before it reaches the silicon.

Comparison table

Model	Standard	RC network	Typical peak current	Test subject	Phase
HBM	JS-001	100 pF / 1.5 k ohm	~1.3 A at 2 kV	Bare component	Silicon qualification
MM	STM5.2 (withdrawn 2018)	200 pF / 0 ohm	~3 A at 200 V	Bare component	Historical, rarely used
CDM	JS-002	Package-dependent	~7 A at 500 V	Bare component	Silicon qualification
IEC 61000-4-2	IEC 61000-4-2	150 pF / 330 ohm	~7.5 A at 4 kV contact	Complete product	Product certification
ISO 10605	ISO 10605	150 pF/330 ohm or 330 pF/2 k ohm	Varies by configuration	Automotive equipment	Product certification

See the glossary for the ESD acronym definitions.

Contact and air test levels

The standard defines four severity levels for each discharge mode. The applicable level is set by the product standard that references IEC 61000-4-2.

Contact discharge

Level	Test voltage	Typical use case
1	2 kV	Lightly disturbed environment, ESD-controlled climate room
2	4 kV	Moderate industrial environment, office equipment
3	6 kV	Severe industrial environment
4	8 kV	Heavily disturbed industrial environment, outdoor
X	As specified by product standard	Special case

EN 55035 imposes level 4 contact discharge (8 kV) for mass-market multimedia. EN 60601-1-2 likewise requires 8 kV contact for medical devices. EN 61000-6-2 (industrial immunity) requires 6 kV contact (level 3).

Air discharge

Level	Test voltage	Typical use case
1	2 kV	Lightly disturbed environment
2	4 kV	Moderate environment
3	8 kV	Severe environment
4	15 kV	Heavily disturbed environment
X	As specified by product standard	Special case

EN 55035 imposes level 4 air discharge (15 kV) for mass-market multimedia. EN 60601-1-2 likewise requires 15 kV air for medical devices. EN 61000-6-2 requires 8 kV air (level 3).

Why air goes higher than contact

Contact discharge is applied through a metal electrode resting on the test point: charge transfer is integral. Air discharge proceeds by arc striking between a pointed electrode and the test point: the transfer depends on humidity, temperature, approach speed, and a fraction of the energy is lost in the arc. At the same voltage level, the injected current is lower in air. To obtain comparable severity in air, the standard requires higher voltages: 15 kV air is roughly equivalent in effect to 8 kV contact, though the correspondence is not exact.

§ § §

Test hardware and setup

An IEC 61000-4-2 campaign mobilises specific equipment, not interchangeable with other EMC tests.

The ESD gun

The ESD gun is the central instrument. It integrates the 150 pF / 330 ohm charging RC network, a high-voltage module adjustable from 0.2 to 30 kV typically, and two interchangeable tips: 8 mm round tip for contact discharge, conical tip for air discharge. Reference manufacturers include EM TEST (dito and ESD30), Teseq/Ametek (NSG 437 and 438), Haefely Hipotronics, Thermo Fisher Keytek. All ship with ISO/IEC 17025 calibration certificates and a mandatory annual calibration cycle.

The ground reference plane

The EUT sits on a 0.8 m high non-conductive wooden table, itself placed on a ground reference plane (GRP). The GRP is a metal sheet of at least 1 m x 1 m, extending at least 0.5 m beyond the EUT on every side, bonded to the building safety earth. The ESD gun return cable connects to the GRP through a low-inductance terminal.

Horizontal and vertical coupling planes

For indirect discharges, two metal planes are added to the setup.

• The HCP (Horizontal Coupling Plane) is a 1.6 x 0.8 m metal sheet on the table beneath the EUT (the EUT itself sitting on a 0.5 mm insulating sheet). The HCP is bonded to the GRP through two 470 k ohm resistors in series. Discharges onto the HCP are applied 10 cm from the EUT edge.
• The VCP (Vertical Coupling Plane) is a 0.5 x 0.5 m metal sheet, bonded to the GRP through two 470 k ohm resistors. The VCP sits 10 cm from each accessible vertical face of the EUT, in turn: front, back, left, right, top if accessible.

Indirect discharges (on HCP and VCP) test how the ESD field couples to the EUT via its cabling and by direct induction, a more realistic scenario than direct discharge when the EUT is protected by a sealed metal enclosure.

Setup diagram

                              ESD gun
                                |
                                v
                   +---[ EUT powered ]------+
                   |  (on 0.5 mm insulator) |
                   |                        |
                   +-----+---HCP plate-----+-----+
                         |   (1.6 x 0.8 m)  |
                         |                  |
                         |  >> 2x 470 kohm  |
                         |                  |
   VCP plate             |                  |
   (0.5 x 0.5 m)         |                  |
   10 cm from EUT        |                  |
   >> 2x 470 kohm        |                  |
                         |                  |
       +-----------------+------------------+--------+
       |       Ground Reference Plane (GRP)          |
       |       (>= 1 x 1 m, bonded to safety earth)  |
       +---------------------------------------------+
                              |
                            Earth

Ambient conditions

Room relative humidity must be between 30 and 60 %, and temperature between 15 and 35 degrees Celsius. Outside that range, repeatability falls, especially in air discharge. The test report logs humidity and temperature hourly.

Test point selection and discharge procedure

The procedure consists in identifying every point accessible to the user in normal operation and in maintenance, then applying the discharges in an ordered sequence.

Test point selection

The test plan typically identifies the following categories:

• Accessible conductive points: exposed metal hardware, connector shells, metallic peripherals. Contact discharge.
• Accessible non-conductive points: screen (glass), plastic front panel, plastic buttons. Air discharge.
• Coupling planes: HCP and VCP. Contact discharge onto the plane (never directly onto the EUT through this path).

On a typical desktop appliance, 10 to 30 points are selected. The selection rationale is recorded in the report.

Procedure and interval

For each test point and each polarity (+ and -), at least 10 successive discharges are applied, with a minimum interval of 1 second between discharges at the same point. The EUT runs its typical application software during the test (for example, an audio appliance plays a test file; a network gateway pushes a packet stream).

Verification between discharges

After each volley of 10 discharges, the observer checks that the EUT still behaves per the applicable criterion (A, B or C). If a non-recoverable loss of function appears (criterion C not met), the test stops and the failure is recorded with the discharge number, point, polarity, and voltage.

Performance criteria A, B and C

This is the core of the evaluation: physical survival of the EUT is not enough; the function must be preserved per a clearly specified category.

Criterion A: no degradation during or after

The EUT keeps operating normally during and after the test. No observable degradation of the main function is tolerated: no glitch on the output, no communication error, no internal counter reset. This is the most demanding criterion, typically applied to safety-critical functions (alarm, emergency stop) and real-time communication functions (industrial protocol transmission).

Criterion B: temporary degradation, self-recovery

The EUT may show a temporary degradation during the test (brief communication interruption, red pixel on screen, one-second measurement error), but it must recover by itself, without user intervention, as soon as the disturbance ends. Typical criterion for secondary functions on multimedia equipment or display functions.

Criterion C: degradation, recovery by user intervention

The EUT may lose a function that requires manual intervention to restore: reset, reboot, cable reconnection. The least demanding criterion, allowed for non-essential functions.

Criterion choice per product standard

Product standard	Applicable criterion for direct discharges
EN 55035 (multimedia)	A for main functions, B for secondary
EN 60601-1-2 (medical)	A or B per patient risk (clinical risk analysis)
EN 61000-6-1 (residential/commercial generic)	B
EN 61000-6-2 (industrial generic)	A for critical outputs, B for the rest
EN 50155 (railway onboard)	A for safety functions, B otherwise

For criterion definitions, see RED tests which covers radio certification, and CE tests for the general EMC framework.

ISO 10605 for automotive

Automotive has its own ESD standard, ISO 10605, sharing the IEC 61000-4-2 philosophy but with parameters adapted to vehicle context.

Two RC networks per scenario

ISO 10605 recognises two discharge scenarios with distinct RC networks:

• User discharge on cabin: 150 pF / 330 ohm network, identical to IEC 61000-4-2. Contact levels 4, 6, 8 kV; air levels 8, 15, 25 kV.
• Discharge during assembly (harness, open connector): 330 pF / 2 k ohm network, simulating discharge from an operator wearing a partially defective ESD wrist strap during assembly. Contact levels 4, 6, 8 kV; air levels 8, 15, 25 kV.

Levels reaching 25 kV air

ISO 10605 reaches 25 kV in air discharge, versus 15 kV for IEC 61000-4-2. This extension reflects the higher triboelectric build-up voltages encountered in automotive (synthetic clothing, textile seats, dry cabin climate in winter). An automotive product must be designed for 8 kV contact and 25 kV air for user discharge, plus assembly tests in parallel.

Procedural differences

ISO 10605 typically requires 3 discharges per polarity per point (vs 10 for IEC 61000-4-2), with a minimum 5-second interval between discharges. The assembly scenario often calls for a pre-conditioning protocol (initial discharge at 8 kV to stabilise the material).

See AEC-Q100/Q101 for ESD robustness at the automotive component level.

IEC 60601-1-2 for medical

Medical applies IEC 61000-4-2 with two specifics: levels are generally the highest (8 kV contact, 15 kV air, level 4), and the performance criterion must be formalised through a clinical risk analysis per ISO 14971. If the temporary loss of a patient monitoring function can cause clinical harm, the applicable criterion shifts from B to A. The dossier must show consistency between the risk analysis and the criterion chosen for each function.

Active implantable devices (cardiac pacemakers, neurostimulators) are tested additionally to ISO 14708-3 with higher ESD levels and specific protocols, outside the scope of this page.

Common pitfalls in campaign preparation

Five mistakes recur in first-pass ESD failure reports.

1. Expired or out-of-range gun calibration. The ESD gun must be calibrated annually against a coaxial target measuring discharge current to ground. An out-of-calibration gun may indicate 8 kV but deliver 6 or 10 kV. The verification is in the calibration certificate provided by the lab before the session.

2. Insufficient interval between discharges. Fast-recharge guns can fire 5 to 10 discharges per second. The standard requires a 1-second minimum, because some failures accumulate thermal stress on TVS diodes and varistors. Firing too quickly produces artificially optimistic results (the component is not in steady thermal state) or pessimistic ones (unrealistic stress accumulation). The lab must enforce a controlled interval.

3. HCP/VCP setup absent or wrongly assembled. Testing an EUT without HCP and VCP makes the direct discharge pass without testing indirect coupling, giving incomplete coverage. The report must show both planes present and bonded through the 470 k ohm resistors. See CE pitfalls for EMC report anomalies.

4. Coiled or poorly arranged cables. The arrangement of power and signal cables changes inductance and stray capacitance, which shape the ESD current path. Testing with cables coiled under the table then shipping the product with cables uncoiled along a wall creates a gap that can produce a market-surveillance failure. The cable arrangement must be photographed and archived.

5. EUT off or in standby during the test. The test must run with the EUT powered and executing its application software. An EUT tested powered off trivially passes: it cannot lose a function it is not executing. The test plan must specify the operating mode (test loop, audio playback, network transmission) and the associated observation criterion.

ESD-robust design

Compliance is not decided at the lab but earlier, on the PCB and enclosure. TVS diodes (Transient Voltage Suppressors) placed as close as possible to inputs and outputs redirect the ESD current to ground before it reaches sensitive components. A TVS with 5 V trigger voltage and 30 W dissipation suits a USB or Ethernet input. Gas discharge tubes (GDT) sit in the first line on ports exposed to very high threat.

The return path for ESD current must be short and low-impedance: continuous ground plane under sensitive signals, ground vias around input points, and separation of ESD-collecting traces from high-speed digital signal traces. A metal enclosure bonded to safety earth is a major protection since it intercepts the discharge before it reaches the electronics. Plastic enclosures compensate with more aggressive circuit protections and common-mode ferrite beads on cabling.

See also

• Surge and Burst (IEC 61000-4-5 / 4-4): EMC transients
• Voltage dips + interruptions (IEC 61000-4-11)
• Harmonics and flicker (IEC 61000-3-2 and 3-3): mains quality
• Radiated emissions EMC test: pre-scan and final scan

ESD-robust design?

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Link to other EMC tests

ESD never runs alone. It belongs to a complete campaign covering all EMC phenomena.

Phenomenon	Standard	Typical residential level
ESD	IEC 61000-4-2	8 kV contact, 15 kV air
Radiated RF field	IEC 61000-4-3	3 V/m, 80 MHz to 6 GHz
Electrical fast transients (EFT)	IEC 61000-4-4	2 kV mains, 1 kV I/O
Surge	IEC 61000-4-5	2 kV differential, 4 kV common
Conducted RF	IEC 61000-4-6	3 V, 150 kHz to 80 MHz
Mains dips and interruptions	IEC 61000-4-11	0 %, 40 %, 70 % at various durations

ESD generally sits first in the sequence: a failure often reveals a structural defect (grounding, shielding) that also shows up on other tests. Solving ESD early avoids re-running several tests after modifications.

Key takeaways

• IEC 61000-4-2 evaluates a complete product under power, with a 150 pF / 330 ohm RC network simulating an operator discharge. Distinct from the HBM, MM and CDM component models that evaluate bare silicon.
• Four contact severity levels (2, 4, 6, 8 kV) and four air levels (2, 4, 8, 15 kV). EN 55035, EN 60601-1-2 and most mass-market standards require level 4 in both modes.
• Three performance criteria, A (no degradation), B (temporary degradation, self-recovered), C (recovery by user intervention), chosen by the product standard based on function criticality.
• The test setup includes a ground reference plane, a horizontal HCP and a vertical VCP, bonded through 2 x 470 k ohm resistors. Indirect discharges on HCP and VCP test radiated coupling.
• ISO 10605 and IEC 60601-1-2 extend IEC 61000-4-2 with levels and criteria suited to automotive and medical respectively.
• Robustness comes from design: TVS protections, PCB layout with continuous ground plane, and conductive enclosure. A product tested only at the lab arrives too late.

For practical application in certification, see CE tests for EU EMC tests, RED tests for radio equipment, and FCC tests for the US side (noting that the FCC does not require immunity testing for Part 15 Subpart B). See also the glossary for ESD acronym definitions.

Sources & references

1. IEC 61000-4-2:2008+AMD1:2017, testing and measurement techniques, electrostatic discharge immunity test , IEC webstore.iec.ch/publication/4189
2. EN 55035:2017+A11:2020, electromagnetic compatibility of multimedia equipment, immunity requirements , CENELEC standards.cencenelec.eu/dyn/www/f?p=205:110:0::::FSP_PROJECT,FSP_ORG_ID:67027,1258635
3. ISO 10605:2008+A1:2014, road vehicles, electrical disturbances from electrostatic discharge , ISO www.iso.org/standard/72428.html
4. EN 60601-1-2:2015+A1:2021, medical electrical equipment, electromagnetic compatibility , IEC webstore.iec.ch/publication/67383
5. ANSI/ESDA/JEDEC JS-001-2023, Human Body Model component-level ESD , JEDEC / ESDA www.jedec.org/standards-documents/docs/jesd22-a114f
6. Directive 2014/30/EU on electromagnetic compatibility , EUR-Lex eur-lex.europa.eu/eli/dir/2014/30/oj