EN 61000-4-2, “Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement techniques – Electrostatic discharge immunity test”, defines how to test the resistance of equipment to static electricity discharges. Laboratories simply call it the “ESD test”; it is the most frequently applied immunity test in EMC testing.
Let us take care of EN 61000-4-2 testing and the CE marking of your product together; CE Danışmanı (CE Consultant) manages the whole process.
What does this test simulate?
A person walking on a carpet, synthetic clothing or a plastic chair charges the human body to several thousand volts. The charge jumps as a spark when the person touches a key, a metal housing or a connector. The ESD test reproduces this discharge in the laboratory and shows whether the equipment freezes, restarts or suffers permanent damage.
The discharge is very short, but its rise time is below one nanosecond; sensitive microcontrollers, touch surfaces and communication ports are therefore the parts most affected.
EN 61000-4-2 at a glance
| Current edition | IEC 61000-4-2:2025 (3rd edition, replacing the 2008 edition); applied in Europe as EN 61000-4-2 |
|---|---|
| Official title | Electromagnetic compatibility (EMC) – Part 4-2: Testing and measurement techniques – Electrostatic discharge immunity test |
| Type of standard | Basic EMC test standard: defines the test method; the level and the performance criterion are set by product and generic standards |
| Legislation | EMC Directive 2014/30/EU; harmonised product and generic standards refer to this test |
Which products does it apply to?
Almost every electrical and electronic product that is touched during use: household appliances, IT and multimedia equipment (EN 55035), lighting, measuring instruments, industrial control panels, medical devices and vehicle electronics.
- Discharges are applied only to points accessible in normal use; boards and connectors behind covers are not tested.
- Ceiling-mounted equipment that is not touched after installation is generally not tested.
- Painted surfaces declared as insulating receive air discharges only.
Test setup
- Generator: the ESD gun represents the human body; its typical values are a 150 pF storage capacitance and a 330 Ω discharge resistor.
- Ground: a metal ground reference plane (GRP) is connected to protective earth. Table-top equipment stands on a 0.8 m non-conductive table, floor-standing equipment on a 0.1 m insulating support.
- Coupling planes: a horizontal coupling plane (HCP) lies on the table and a 0.5 × 0.5 m vertical coupling plane (VCP) stands 0.1 m from the equipment. Both are connected to the GRP through cables with two 470 kΩ resistors; the equipment is separated from the HCP by 0.5 mm of insulation.
- Direct discharge: the gun is applied to the accessible points of the equipment. Contact discharge is preferred; air discharge is used where contact is not possible.
- Indirect discharge: to represent discharges to objects near the equipment, contact discharges are applied to the edge of the HCP and to the centre of the VCP.
- Number and interval: unless the product standard states otherwise, 10 single discharges per point and polarity, at least 1 s apart. For air discharge all levels up to the target are applied; for contact discharge only the target level.
Test levels
| Level | Contact discharge | Air discharge |
|---|---|---|
| 1 | 2 kV | 2 kV |
| 2 | 4 kV | 4 kV |
| 3 | 6 kV | 8 kV |
| 4 | 8 kV | 15 kV |
The generic standards for residential and industrial environments require ±4 kV contact and ±8 kV air discharge; your product standard sets the exact level. The voltages of the two methods differ, but their severities are not considered equivalent.
Performance criteria
- A: the equipment works normally within its specified limits, also during the discharge.
- B: temporary degradation that recovers by itself. The generic standards require this criterion for ESD.
- C: temporary loss of function that needs user action or a restart.
- D: damage to hardware or software, or loss of data. The test is failed.
In every case the equipment must not become unsafe as a result of the test; this is assessed together with the Low Voltage Directive safety evaluation.
Place in the CE marking process
- The EMC standard of the product is identified; the ESD level, the application points and the criterion are read from it.
- Housing earthing, connector protection and TVS diodes are reviewed during design; a pre-test is run if needed.
- The test is carried out in an accredited laboratory; the report records the application points, the number of discharges and the climatic conditions.
- The report goes into the technical file; the EU Declaration of Conformity under the EMC Directive is drawn up and the product is CE marked.
Standards applied together
- EN 61000-4-4: electrical fast transient (burst) immunity
- EN 61000-4-5: surge immunity
- EN 61000-4-3: radiated RF field immunity
- EN 61000-6-1 and EN 61000-6-2: generic immunity for residential and industrial environments
Frequently asked questions
What is the difference between contact and air discharge?
In contact discharge the tip of the gun touches the equipment and the discharge is triggered by a switch; it is the preferred method because it is highly repeatable. In air discharge the charged tip approaches the equipment and the spark jumps through the air; it is used for insulating surfaces and points such as displays that cannot be touched by the tip.
Does humidity affect the test?
Yes. As the humidity falls, the peak value of the discharge current rises. The standard allows testing below 30 % relative humidity; if the equipment meets the criterion under these conditions, no further action is needed.
What if my product fails?
The input and interface stages are usually strengthened: TVS diodes are added to connector pins, metal parts are bonded to the chassis with a low impedance, clearances at the board edge are increased and a watchdog is added to the firmware. The test is then repeated at the same points.
Other standards in this group
- EN 61000-4-6: Conducted RF Immunity Test
- EN 61000-4-11: Voltage Dips and Interruptions Test
- EN 61000-4-3: Radiated RF Field Immunity Test
- EN 61000-4-4: Electrical Fast Transient Burst Test
