IEC 61000-4-8 magnetic field immunity: 1 to 100 A/m

Hugues Orgitello updated 7 Oct 2026 15 min read

The IEC 61000-4-8 test checks immunity to the 50/60 Hz magnetic field with a calibrated induction coil: five severity levels from 1 to 100 A/m (plus an open level X), short-duration fields of 300 and 1 000 A/m at the two highest levels, and three orthogonal axes. The field produced by transformers, motors, distribution cabinets and high-current chargers penetrates enclosures and couples into PCBs. Product standards such as EN 55035 (multimedia), the generic EN 61000-6-1 and 6-2, and IEC 60601-1-2 (medical, 30 A/m for equipment with magnetically sensitive parts) reference this test and set the level and the performance criterion. This page lays out the standards framework (Edition 2.0 of 2009), the severity levels, the geometry of induction coils, the test procedure on the three orthogonal axes, the performance criterion, the connection to IEC 61000-4-9 (pulsed field) and 4-10 (damped oscillatory field), and the campaign pitfalls.

TL;DR:

• Five severity levels for the continuous field: 1, 3, 10, 30 and 100 A/m, plus an open level X; a short-duration field of 1 to 3 s adds 300 A/m at level 4 and 1 000 A/m at level 5.
• Three orthogonal orientations are mandatory, by rotating the EUT 90 degrees or by switching the coil orientation.
• The performance criterion comes from the product standard: product standards generally ask criterion A for the continuous field.
• IEC 60601-1-2 asks 30 A/m for medical equipment with magnetically sensitive parts, in every environment; its 2020 amendment also added proximity magnetic fields per IEC 61000-4-39.

Why a low-frequency magnetic immunity test

Electromagnetic compatibility splits phenomena into three families: high-frequency fields and currents (radiated and conducted tests above 150 kHz), fast transients (ESD, EFT, surge), and low-frequency fields close to mains. The last family is covered by IEC 61000-4-8 and its neighbours 4-9 and 4-10.

The magnetic field at 50 or 60 Hz is present wherever a significant alternating current flows: a distribution transformer cell typically generates 5 to 50 A/m at one metre, a 10 kW motor produces 1 to 5 A/m at the same distance, an automation cabinet with busbar reaches 10 to 30 A/m at 0.5 metre. These levels correspond to the real environment of industrial or medical equipment installed near electrical infrastructure.

Why a low-frequency field disturbs electronics

At 50 Hz the wavelength is 6000 km. No antenna or resonant-cavity coupling is at play. The coupling mechanisms are quasi-static. The field penetrates metallic enclosures through apertures (vents, ventilation slots, discontinuous gaskets), because the skin depth in mild steel at 50 Hz is roughly 0.8 mm: a 1 mm sheet attenuates by only a few decibels.

Once inside, the field couples into PCB current loops. A 10 cm square loop exposed to 10 A/m at 50 Hz picks up roughly 50 microvolts peak, which sounds modest but is enough to disturb a 24-bit measurement sensor, a class AB audio amplifier, a Hall sensor or a sensitive relay. Legacy CRT displays were the first victims (beam deflection visible at 1 A/m), but the topic stays current for electron microscopes, precision balances, biomedical signal amplifiers and resistive current sensors.

Standards framework: IEC 61000-4-8 Ed 2.0:2009

The edition in force is IEC 61000-4-8 Ed 2.0:2009, superseding Edition 1.0 of 1993 and its 2000 amendment. Its scope is immunity to magnetic disturbances at the power frequencies of 50 Hz and 60 Hz; it defines the recommended test levels, the test equipment and setup, and the procedure, and leaves the choice of level and performance criterion to product committees.

Product standards that reference IEC 61000-4-8

Product standard	Required level	Criterion	Justification
EN 55035 (multimedia)	Set in its enclosure-port table	Per the standard	Applies only to equipment containing devices susceptible to magnetic fields
EN 55024 (IT equipment, legacy pre-CISPR 35)	1 A/m	A	Office IT equipment
EN 61000-6-1 (generic residential)	3 A/m	A	Generic residential/commercial standard
EN 61000-6-2 (generic industrial)	30 A/m	A	Severe industrial environment
EN 60601-1-2 (medical, 4th edition with AMD1:2020)	30 A/m at 50 or 60 Hz, one value for both healthcare environments	Per the standard	Applies to equipment with magnetically sensitive components or circuitry; raised from 3 A/m in the 3rd edition
EN 50121-4 (railway signalling and telecom apparatus)	Per the standard, including the 16.7 Hz traction frequency where relevant	Per the standard	Railway environment

IEC 60601-1-2 is the case most often misquoted. Its 4th edition raised the power-frequency level from 3 to 30 A/m, and the 2020 amendment (AMD1) restates the row in the enclosure-port table as a single "30 A/m, 50 Hz or 60 Hz" for equipment with magnetically sensitive components or circuitry, with no lower value for home healthcare. The same amendment added a second magnetic test, proximity magnetic fields to IEC 61000-4-39, aimed at sources such as RFID readers and wireless chargers:

Proximity test frequency (IEC 60601-1-2, Table 11)	Modulation	Immunity test level
30 kHz	CW	8 A/m
134.2 kHz	Pulse modulation, 2.1 kHz	65 A/m
13.56 MHz	Pulse modulation, 50 kHz	7.5 A/m

The 30 kHz test applies only to equipment intended for the home healthcare environment, and, as with power-frequency fields, the test targets equipment with magnetically sensitive components or circuitry; the location of the applied field is set in the test plan and recorded in the report.

Frequencies covered

The scope of IEC 61000-4-8 is the power frequencies of 50 Hz and 60 Hz: 50 Hz in Europe and most of the world, 60 Hz in North America and parts of Japan. Other frequencies come from product or sector standards, not from IEC 61000-4-8 itself:

• 16.7 Hz for the 15 kV traction networks of Germany, Austria, Switzerland, Sweden and Norway, where railway standards call for it.
• 400 Hz for aircraft and some military equipment, under their own environmental test standards.

See the glossary for the EMC acronyms, and CE tests for the general EMC framework in the EU.

What are the IEC 61000-4-8 test levels?

The standard defines five severity levels. The applicable level is set by the product standard.

Level	Continuous field intensity	Short-duration intensity	Typical environment
1	1 A/m	-	Residential far from industrial sources
2	3 A/m	-	Typical residential and commercial
3	10 A/m	-	Moderate industrial
4	30 A/m	300 A/m (1 to 3 s)	Severe industrial, medical critical care
5	100 A/m	1 000 A/m (1 to 3 s)	Heavy industrial, close to high-current busbars
X	Specified by product standard	Specified	Special case

The short-duration level (column 3) applies in addition to the continuous field at levels 4 and 5 only, and simulates transient phenomena associated with a short-circuit or a motor start. It runs for 1 to 3 seconds, or in a variant 1 to 10 cycles of the mains frequency (20 to 200 ms at 50 Hz).

Quick read for the designer

For a consumer product certified to EN 55035, the requirement is typically 1 A/m: a permissive level, reachable without special precautions. For an industrial product certified to EN 61000-6-2, the requirement rises to 30 A/m: this calls for magnetic shielding considerations, orientation of sensitive loops, and filtering on analogue sensors. For a medical device intended for critical care (EN 60601-1-2 in a professional healthcare environment), 30 A/m is mandatory and requires a robust architecture from the PCB upward.

Test hardware and configuration

An IEC 61000-4-8 campaign relies on a high-power mains-frequency generator, a calibrated induction coil and an EUT-positioning system.

The generator

The generator supplies alternating current at the test frequency (50 or 60 Hz, or another frequency where the product standard asks for it). To produce 30 A/m at the centre of a 1 m by 1 m coil, typically 24 to 30 A are needed in a single-turn coil. Frequency stability and harmonic content are controlled: THD below 8 percent is required by the standard. The reference manufacturers are EM TEST (MIG 5060 and MIG OS6), Teseq/Ametek (ECOS and NSG 1007).

The induction coil

Three geometries are specified:

• Single square coil 1 m by 1 m, single thick-section turn on a non-magnetic frame. Typical calibration constant: 0.87 A/m per ampere injected at centre.
• Single rectangular coil 1 m by 2.6 m, for larger EUTs. Different constant, supplied by the manufacturer.
• Two-element Helmholtz coils, two parallel coils separated by their radius, producing a very uniform field in the central volume. More accurate but bulkier.

The coil holds an annual calibration certificate giving the field map inside its usable volume (typically the central 50 percent of the bounding volume), with the uniformity tolerance per the standard (plus or minus 3 dB).

Configuration diagram

                    +-------------------------------+
                    |  Induction coil (1 turn)      |
                    |  geometry 1 m x 1 m           |
                    |                               |
                    |  +-------------------+        |
                    |  |                   |        |
                    |  |   EUT energised   |        |
                    |  |   centred in the  |        |
                    |  |   uniform volume  |        |
                    |  |                   |        |
                    |  +-------------------+        |
                    |        |                      |
                    |        | 90 deg rotations     |
                    |        | X, Y, Z              |
                    |        v                      |
                    +-------------------------------+
                            |          |
                            |          |
                       +------------+  |
                       | Generator  |  |
                       | 50/60 Hz   |  |
                       | I = 0 to 30A| |
                       +------------+  |
                            |          |
                            +--- GRP ---+
                                  |
                                Earth

  Orientations to test (3 orthogonal axes):
    X horizontal       Y horizontal           Z vertical
    [EUT]              [EUT rotated 90 deg]   [EUT rotated 90 deg]

Ambient conditions and EUT setup

The EUT sits on a non-conductive wooden table or non-magnetic support, centred in the uniform volume of the coil. The test room must be away from ambient-field sources above 1 A/m, which excludes immediate proximity to HV-to-LV transformers or unshielded distribution panels. The report logs the ambient field before and after the test.

The EUT runs its typical application software during the test (simulated ECG trace, sensor bus traffic, network packet stream). The observation setup must detect any degradation, even brief.

How is the test performed? The three orthogonal axes

The test consists of applying the field at the specified intensity in the three orthogonal orientations in turn, observing the EUT during and after each sequence.

Standard sequence for a continuous level

For a level 4 test (30 A/m) the procedure is:

1. EUT stabilisation. The EUT is energised, its application software runs, and the observation is verified as nominal for at least 1 minute.
2. Orientation 1 (X horizontal). The field is established at 30 A/m, held for 1 to 3 seconds after stabilisation, then cut. The observation is verified during and after.
3. 90 degree rotation. The EUT is rotated about a vertical axis to expose Y to the field direction.
4. Orientation 2 (Y horizontal). The cycle repeats: field established, held, cut, observed.
5. 90 degree rotation about a horizontal axis. The EUT is tilted to expose Z (vertical) to the field direction.
6. Orientation 3 (Z vertical). The cycle repeats.

A common variant: instead of rotating the EUT, the coil is rotated, or a three-orthogonal-coil system is used and the excitation is switched between them. The physical result is equivalent.

Sequence for the short-duration level

When the product standard specifies the short-duration level (levels 3 or 4), a second sequence follows the continuous sequence: the field is applied at the transient amplitude (100 or 300 A/m) for 1 to 3 seconds, or for 1 to 10 cycles of mains frequency (20 to 200 ms at 50 Hz), per the product specification. This mode simulates a nearby short-circuit or a high-power motor start.

Observation and acceptance

The observer verifies the EUT's primary function during each application of the field and during the 1 to 3 seconds after the cut. Any degradation, even brief, is logged with the orientation, the level and the nature of the observation (communication loss, measurement artifact, analogue output drift).

Performance criterion: set by the product standard

As a basic EMC publication, IEC 61000-4-8 does not itself impose a performance criterion: the product standard does. In practice most product standards ask criterion A for the continuous field, and the reason is physical. A power-frequency magnetic field is not a transient in the real environment: equipment installed near a transformer stays exposed for years, so a degradation tolerated in the lab would be a permanent degradation on site.

The short-duration field (300 A/m at level 4, 1 000 A/m at level 5, for 1 to 3 seconds) represents fault conditions such as a short-circuit current, and product standards that use it may accept a different criterion for it. Read the criterion in the product standard you test against rather than assuming one.

The magnetic family: 4-8 vs 4-9 vs 4-10

Three IEC 61000-4-x tests cover magnetic phenomena. Their relationship is summarised below.

Test	Simulated phenomenon	Levels	Duration	Criterion	Typical product standard
IEC 61000-4-8	Continuous power-frequency magnetic field (50/60 Hz)	1 to 100 A/m continuous; 300 and 1 000 A/m short-duration	Continuous, 1 to 3 s	Per product standard, usually A	EN 55035, IEC 60601-1-2, EN 61000-6-2
IEC 61000-4-9	Pulsed magnetic field (nearby lightning strike, short-circuit)	100 to 1000 A/m peak	6.4/16 microsecond pulse	B	EN 61000-6-5 (substations), EN 61000-6-2
IEC 61000-4-10	Damped oscillatory magnetic field (HV switching)	10 to 100 A/m peak	100 kHz or 1 MHz oscillation	B	EN 61000-6-5, severe industrial EN 61000-6-2

IEC 61000-4-9, pulsed field

The 4-9 test simulates the magnetic effect of a very high fault current (distribution short-circuit, nearby lightning). The pulse has a 6.4 microsecond front and 16 microsecond half-duration, with peaks up to 1000 A/m at level 5. Criterion B applies, the phenomenon being transient. Mainly relevant for HV substations and severe industrial environments.

IEC 61000-4-10, damped oscillatory field

The 4-10 test simulates HV breaker or disconnector switching, which generates a damped oscillation at 100 kHz or 1 MHz. Peak 100 A/m at level 5. Criterion B applies. Mainly relevant for substation equipment.

For neighbouring EMC tests, see ESD per IEC 61000-4-2, surge and burst per IEC 61000-4-5 and 4-4, and mains dips and interruptions per IEC 61000-4-11.

The medical case: 30 A/m in IEC 60601-1-2

IEC 60601-1-2 is the product standard most often misquoted on this test. Its 4th edition raised the power-frequency level from 3 to 30 A/m, and Amendment 1 of 2020 restates the row of the enclosure-port table (Table 4) as a single value: 30 A/m at 50 Hz or 60 Hz, applicable to medical electrical equipment with magnetically sensitive components or circuitry. There is no lower value for the home healthcare environment, and no separate ICU or operating-room level.

The performance criterion for each function comes from the manufacturer's risk management: if loss of a function under the field could harm the patient, that function has to keep working. The justification belongs in the risk-management file and in the test report.

The same amendment added proximity magnetic fields to IEC 61000-4-39; see the table in the product-standards section above.

See also

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

Working on low-frequency EMC immunity (IEC 61000-4-8, 4-9, 4-10) for medical devices and industrial equipment in severe environments for a real product? AESTECHNO can audit your design and certification plan. Get in touch

Common campaign pitfalls

Six errors recur in first-pass failure reports for the 4-8 test.

1. EUT positioned outside the uniform volume. The coil produces a uniform field in only the central 50 percent of its bounding volume, with a plus or minus 3 dB tolerance. An EUT placed near the coil edge receives a weaker field than expected, and the lab may wrongly conclude the EUT is compliant. The test plan must specify positioning and the report must photograph it.

2. One of the three orientations omitted. The classic pitfall on flat-lay EUTs is to forget the vertical axis, which requires a rotation about a horizontal axis that is not always practical. Testing X and Y without Z passes an EUT that would have failed on Z. The report must photograph all three rotations.

3. Coil calibration out of date. The coil's A/m-per-ampere constant drifts if the frame deforms, if the turn is displaced, or if a magnetic mass has been added nearby. Annual calibration is mandatory, and absence of ferromagnetic mass within 2 metres is documented.

4. EUT in standby or out of nominal mode. Equipment tested in standby exercises few sensitive functions and often passes trivially. The test plan must specify the operating mode (measurement loop, simulated ECG capture, active network transmission) and the observation criterion.

5. High generator THD. A generator with THD above 8 percent injects harmonics that couple differently than pure 50 Hz. The standard requires THD below 8 percent at rated current; the measurement is logged in the report.

6. Ambient field not measured. The test room must have an ambient field below 1 A/m. A room near an unshielded distribution transformer can exceed that. Measuring the ambient field before and after the test is mandatory. See CE pitfalls for general EMC reporting anomalies.

Robust design for low-frequency magnetic fields

Compliance with 4-8, especially at the 30 A/m level, is decided upstream by PCB and enclosure design.

Reduce sensitive current loops

Any closed current loop on a PCB picks up an electromotive force proportional to the area, the field intensity, and the frequency. At 50 Hz and 30 A/m, a 100 square cm loop picks up roughly 170 microvolts peak. Reducing the loop area (signal return routed close to the forward path, continuous ground plane) reduces the induced parasitic voltage proportionally.

Orientation of sensitive components

Components with a strong magnetic coupling factor (relay coils, measurement transformers, Hall sensors, moving-coil microphones) have a sensitive direction. Orienting them so their sensitive axis is perpendicular to the most likely orientation of the external field reduces coupling. This optimisation targets a specific axis, but the three-orthogonal-axes test verifies that the EUT survives in any orientation.

Magnetic shielding

Mild-steel enclosures attenuate poorly at 50 Hz (0.8 mm skin depth, a few dB per millimetre). For significant shielding, high-permeability materials are needed: mumetal, permalloy, low-frequency ferrites. A 0.5 mm mumetal shield can reach 30 to 40 dB attenuation at 50 Hz, but the material is expensive, fragile, and loses its properties after bending if not annealed. A full mumetal envelope is typically reserved for very-high-precision instruments.

Filtering and software integration

On analogue sensors, a low-pass filter with cutoff below 50 Hz attenuates the induced parasitic. On ECG or audio measurements, a 50 Hz notch is standard. In software, averaging over 20 or 40 ms windows (one or two mains periods) removes the residual magnetic component.

What to remember

• IEC 61000-4-8 Ed 2.0:2009 evaluates immunity to a continuous magnetic field at the power frequencies of 50 and 60 Hz.
• Five severity levels: 1, 3, 10, 30 and 100 A/m, plus an open level X. A short-duration field of 1 to 3 seconds adds 300 A/m at level 4 and 1 000 A/m at level 5.
• Three orthogonal orientations mandatory, by EUT rotation or by orthogonal-coil switching.
• The criterion comes from the product standard; most ask criterion A for the continuous field, because the phenomenon is permanent in the real world.
• IEC 60601-1-2 asks 30 A/m at 50 or 60 Hz for medical equipment with magnetically sensitive parts, with one value for professional and home healthcare, and adds proximity magnetic fields per IEC 61000-4-39 since 2020.
• IEC 61000-4-9 and 4-10 complete the magnetic family: 4-9 pulsed (lightning, short-circuit), 4-10 damped oscillatory (HV switching). Both accept criterion B.
• Robustness comes from design: smaller sensitive current loops, oriented relay coils and Hall sensors, mumetal shielding for extreme cases, low-pass and 50 Hz notch filtering on sensitive sensors.

For practical certification, see CE tests for the EU EMC framework, RED tests for radio, and the glossary.

Sources & references

1. IEC 60601-1-2:2014/AMD1:2020, Table 4 and Table 11 (public sample), IEC via iTeh Standards cdn.standards.iteh.ai/samples/100132/e7d4039bdb1f4559aa3c012ff789f5b6/IEC-60601-1-2-2014-AMD1-2020.pdf
2. IEC 61000-4-8 Ed 2.0:2009, power-frequency magnetic field immunity test, IEC webstore.iec.ch/publication/4229
3. EN 60601-1-2:2015+A1:2021, medical devices, electromagnetic compatibility, IEC webstore.iec.ch/en/iec-search/result?q=EN%2060601-1-2
4. EN 55035:2017+A11:2020, multimedia equipment, electromagnetic immunity, CENELEC standards.cencenelec.eu/dyn/www/f?p=205:110:0::::FSP_PROJECT,FSP_ORG_ID:67027,1258635
5. EN 55024:2010+A1:2015, information technology equipment, immunity, CENELEC standards.cencenelec.eu/dyn/www/f?p=205:110:0::::FSP_PROJECT,FSP_ORG_ID:35375,25
6. IEC 61000-4-9, pulsed magnetic field immunity test, IEC webstore.iec.ch/publication/4231
7. Directive 2014/30/EU on electromagnetic compatibility, EUR-Lex eur-lex.europa.eu/eli/dir/2014/30/oj