IEC 61000-4-39 Proximity Magnetic Field Immunity Testing for Medical Devices

Many active medical devices contain components or circuits that respond to magnetic fields, and in everyday use they may be held next to an RFID reader, wheeled through a shop's anti-theft gate, placed on a wireless charging pad or brought close to an NFC device. These fields are non-uniform and fall off quickly with distance. The introduction to IEC 61000-4-39 notes that existing radiated immunity methods such as IEC 61000-4-3 may not be suitable for such close-proximity fields, and the power-frequency magnetic field test runs only at 50 Hz or 60 Hz. Amendment 1 to IEC 60601-1-2, published in 2020, added subclause 8.11 and Table 11 for this purpose, using the test methods of IEC 61000-4-39. This article covers the field sources, the Table 11 test points, when testing can be skipped, how the test is run and judged, and where SUNGO performs it.

The short answer

• IEC 61000-4-39 is the basic EMC standard for immunity to radiated fields in close proximity, covering 9 kHz to 6 GHz. Its 9 kHz to 26 MHz part is magnetic field immunity, applied with a radiating loop. GB/T 17626.39-2023 is the identical Chinese adoption of IEC 61000-4-39:2017.
• For medical electrical equipment, IEC 60601-1-2:2014+A1:2020 subclause 8.11 and Table 11 set three test points: 30 kHz (home healthcare equipment only), 134.2 kHz and 13.56 MHz.
• Subclause 8.11 sets out a four-step evaluation. Equipment with no magnetically sensitive parts, sufficient separation or an acceptable exposure risk need not be tested; manufacturers may also go straight to testing.
• The field is applied only to enclosure and accessory surfaces accessible during intended use, and the locations go into the test plan and test report. Results are judged against basic safety and essential performance.
• China's YY 9706.102-2021 is, per its cover and foreword, a modified adoption of IEC 60601-1-2:2007 and contains no such test, so this article does not treat the test as mandatory for Chinese registration; any separate evaluation is for the reviewing authority to decide.
• At SUNGO the test is performed by the Hefei laboratory. The standards in the scope table below are within its IAS accreditation scope (TL-1119), listed as whole standards without edition years. Confirm with the laboratory which edition (e.g. IEC 60601-1-2 including Amendment 1) the IAS report will cite.

Standards and scope

IEC 61000-4-39: the basic standard

Edition 1.0 of IEC 61000-4-39 was published in March 2017 by IEC subcommittee 77B (high frequency phenomena) of technical committee 77 (electromagnetic compatibility), as a basic EMC publication under IEC Guide 107. It specifies immunity requirements, test levels and test procedures for equipment exposed to radiated energy from RF transmitters used in close proximity, over 9 kHz to 6 GHz. "Close proximity" generally means 200 mm or less for RF fields above 26 MHz and 500 mm or less for magnetic fields below 26 MHz.

It does not replace the general radiated immunity requirements of IEC 61000-4-3 and applies only where equipment is exposed to sources in close proximity. It is an independent test method, and other methods are not to be substituted for it when claiming compliance. As a basic standard it leaves applicability, test levels and performance criteria to product committees; for medical electrical equipment, that means IEC 60601-1-2.

The standard splits the spectrum into ranges: 9 kHz to 150 kHz and 150 kHz to 26 MHz for magnetic field immunity using radiating loops; 26 MHz to 380 MHz, for which edition 1.0 does not yet define a test; and 380 MHz to 6 GHz, using a TEM horn antenna. This article covers only the magnetic part.

GB/T 17626.39-2023 and EN 61000-4-39

The Chinese counterpart, GB/T 17626.39-2023 (Radiated fields in close proximity immunity test), is a recommended national standard published on 2023-12-28 and implemented on 2024-07-01. It is an identical adoption of IEC 61000-4-39:2017 under the national EMC standardization committee TC246. The European number is EN 61000-4-39. The Hefei laboratory's IAS certificate lists the IEC, EN and GB/T numbers.

IEC 60601-1-2 subclause 8.11

IEC 60601-1-2 Edition 4.0 was published in February 2014 and Amendment 1 in September 2020; the consolidated text is Edition 4.1. Proximity magnetic field immunity is new in the amendment, which adds IEC 61000-4-39:2017 to the normative references, adds a "proximity magnetic fields, see 8.11" row to the enclosure port table (Table 4), introduces subclause 8.11 (9 kHz to 13.56 MHz) and Table 11, and adds Table 10 item 38: where testing is performed, the locations of field application are recorded in the test report.

The US FDA Recognized Consensus Standards database lists IEC 60601-1-2 Edition 4.1 (2020-09) under recognition number 19-36 with partial recognition; the parts not recognized, an environment example in Figure 3 and a footnote citation in Table 8, do not concern subclause 8.11 (checked on 2026-10-22).

China and the EU

YY 9706.102-2021 is China's mandatory industry standard for EMC of medical electrical equipment, published on 2021-03-09 and implemented on 2023-05-01, replacing YY 0505-2012. Its cover and foreword state that it is a modified adoption of IEC 60601-1-2:2007, whereas proximity magnetic field immunity only entered IEC 60601-1-2 with Amendment 1 in 2020. Its normative references cite GB/T 17626.2, .3, .4, .5, .6, .8 and .11 for immunity but not GB/T 17626.39, and its text has no proximity magnetic field clause. Whether a product needs a separate evaluation for Chinese registration is best confirmed with the reviewing authority or the registration testing institution. For the EU, which edition of EN 60601-1-2 gives a presumption of conformity is set by the list of harmonised standards in the Official Journal of the European Union; confirm the edition to use with your notified body.

Where proximity magnetic fields come from

The introduction of IEC 61000-4-39 notes that new technologies also use magnetic fields, which are non-uniform and vary considerably in magnitude and direction. Typical sources include motors, power transformers, switching power supplies, higher-powered electronic article surveillance (EAS) gates, RFID transmitters, inductive charging systems and NFC devices, and their fields decrease rapidly with distance.

The 13.56 MHz point in Table 11 is the NFC centre frequency: ISO/IEC 18092 defines NFCIP-1 for inductively coupled devices operating at a centre frequency of 13.56 MHz. Informative Annex B of IEC 61000-4-39 is titled "Test frequencies, levels and modulations", with B.2 covering magnetic emitters in the range from 9 kHz to 26 MHz; see the standard for details. Other magnetic sources at the intended use location, such as induction heating equipment, can be addressed separately in risk management; step c) of subclause 8.11 covers only the Table 11 frequencies, field strengths and modulations.

Table 11: test frequencies, modulation and field strength

Table 11 of IEC 60601-1-2:2014+A1:2020, "Test specifications for ENCLOSURE PORT IMMUNITY to proximity magnetic fields", is as follows (as given in Amendment 1; visible in the publicly available preview):

• Note a: only for ME equipment and ME systems intended for use in the home healthcare environment.
• Note b: the carrier is modulated with a 50 % duty cycle square wave.
• Note c: r.m.s. value before modulation is applied.

Table 1 of the amendment allows the test at any one power input voltage and any one power frequency within the rated range. Against the ranges of IEC 61000-4-39, 30 kHz and 134.2 kHz fall in the 9 kHz to 150 kHz range and 13.56 MHz in the 150 kHz to 26 MHz range.

Evaluate before deciding whether to test

Subclause 8.11 sets out four steps, and the manufacturer may go directly to step d). The result of each applicable step must be documented in the test report or the risk management file.

1. a) Magnetically sensitive parts: equipment with no magnetically sensitive components or circuitry in the enclosure or an attached accessory needs no further evaluation.
2. b) Separation distance: where the enclosure or accessory design ensures, during intended use, at least 0.15 m between those components and the Table 11 field sources, no further evaluation is needed.
3. c) Risk analysis: otherwise, analyse the risk of exposure to the Table 11 frequencies, field strengths and modulations at less than 0.15 m. If the risk is acceptable, the Table 11 tests need not be performed.
4. d) Testing: equipment meeting neither b) nor c) is tested to Table 11 using the methods of IEC 61000-4-39.

Subclause 8.11 does not list which components count as magnetically sensitive. Engineers need to judge that from the circuit and mechanical drawings, including distances to accessible surfaces, and keep the rationale. If the evaluation is weakly supported, testing may still be needed later.

How the test is performed

Radiating loop and level setting

IEC 61000-4-39 generates the non-uniform field with a radiating loop antenna. Clause 6.1 specifies the test equipment for 9 kHz to 150 kHz and for 150 kHz to 26 MHz separately, and clauses 8.5.1 and 8.5.2 give the level setting procedure for each range: the loop's field is set to the required level before it is applied to the equipment. Loop dimensions, calibration arrangement and tolerances are as given in the standard.

Test windows and test distance

Rather than immersing the equipment in a uniform field, the radiating loop is applied close to the surface, one "test window" at a time over the selected regions. Table 4 of the standard defines window size and test distance, and the standard's two example figures for radiating loop testing are captioned with a 100 mm x 100 mm window (9 kHz to 150 kHz) and an 80 mm x 80 mm window (150 kHz to 26 MHz). The test distance, window layout and execution are as specified in clauses 7.1 and 8.5.3.

Which surfaces are tested

Step d) of subclause 8.11 applies the field only to enclosure or attached-accessory surfaces accessible during intended use. Test windows may be chosen to illuminate only the area of the magnetically sensitive components, and the locations should be specified in the test plan and must be recorded in the test report.

In practice, mark the magnetically sensitive parts on the drawings so the windows can be aimed at them; otherwise all accessible surfaces need covering, which adds considerably to the test effort. Also state in the test plan which parts of cables, sensors, handles and probes count as accessible accessory surfaces.

Operating mode and monitoring

Run the equipment in the mode most likely to show an effect on essential performance and monitor it throughout. Where the device itself includes radio equipment such as an NFC or RFID module, communication may not be possible when it is tested in its passband; the amendment states that basic safety and essential performance must still be provided.

Judging results: back to essential performance

Under IEC 60601-1-2 the equipment must continue to provide basic safety and essential performance during the test. How clearly results can be judged therefore depends on how essential performance was defined and whether the acceptance criteria can be observed or measured at the bench: permitted deviation, whether an alarm is acceptable, whether automatic recovery is required, and whether recovery needing operator action counts as a pass.

If an anomaly occurs, identify the frequency and window that triggered it, then trace the coupling path in the circuit and mechanical design. For diagnosis, fixes and retest scope, see EMC Failures: Locating the Cause, Fixing It, Scoping the Retest. The Hefei laboratory's IAS scope also includes IEC TS 60601-4-2 (guidance and interpretation on electromagnetic immunity performance), which can be referenced in the test plan if needed.

How this differs from power-frequency magnetic field immunity

The row next to proximity magnetic fields in Table 4 of IEC 60601-1-2 is power-frequency magnetic field immunity: IEC 61000-4-8 at 30 A/m, 50 Hz or 60 Hz, with the field frequency matching the equipment's power frequency. IEC 61000-4-8 (Edition 2.0, 2009-09) attributes this field to power-frequency current in conductors or, less often, to sources such as transformer leakage, and describes immersion (equipment at the centre of an induction coil) and proximity (a small coil moved along the equipment to find sensitive areas) methods. The proximity magnetic field test addresses localised, non-uniform fields above 9 kHz close to the surface, so frequencies, modulation, application method and exemption logic all differ. One does not substitute for the other; list both separately in the test request.

Accreditation scope table

Entries relevant to this article from the Hefei laboratory's IAS scope of accreditation (TL-1119), as they appear on the certificate:

Where the work is done at SUNGO, and under which accreditation

• Location: the Hefei laboratory, Zipeng Town, Feixi County, Hefei, Anhui Province, China.
• Legal entity: Hefei SUNGO Medical Technology Co., Ltd., an independent company.
• Accreditation: the standards listed in the table above are within the Hefei laboratory's IAS accreditation scope (TL-1119), listed as whole standards without edition years. If you need an IAS report to a specific edition, for example IEC 60601-1-2 including Amendment 1, confirm the edition with the laboratory before ordering.
• Shanghai laboratory: Shanghai SUNGO Medical Technology Co., Ltd. is a separate legal entity with its laboratory at 958 Kangqiao East Road, Pudong, Shanghai. The standards in the table above are not in its accreditation scope.

Acceptance of a report by a particular regulator or notified body depends on that body's requirements; confirm them with your regulatory agent or the reviewing authority before choosing the standard numbers and edition for the report.

Preparing for testing

• Markets and editions: target markets and the standard numbers required (IEC, EN or GB/YY) with edition years; the edition used for the report is confirmed when the order is accepted.
• Subclause 8.11 evaluation: a list of magnetically sensitive components or circuits, with positions and distances to accessible surfaces marked on the drawings, plus the relevant risk management file extract if steps a) to c) were evaluated.
• Intended use environment: whether the device is intended for the home healthcare environment, which decides whether 30 kHz applies.
• Accessories and surfaces: attached accessories (cables, sensors, probes, handles) and the surfaces accessible during intended use.
• Essential performance: its definition, bench-checkable acceptance criteria and the monitoring method, with any dedicated monitoring software or fixtures.
• Operating modes: the modes to cover; for built-in RFID, NFC or wireless charging, the operating bands and how to switch modes.
• Samples: production-equivalent units with a fixed, declared firmware version, supplied with power adapters, batteries and other items needed for operation.

Sample quantity and fixtures depend on product design and the clauses selected; they are confirmed when the order is accepted.

FAQ

Our device has no magnetically sensitive components. Do we still need the test?

Under step a) of subclause 8.11, no further evaluation is needed. Record the conclusion and its basis in the test report or the risk management file.

Is the 30 kHz test always required?

No. Note a) to Table 11 limits 30 kHz to equipment intended for the home healthcare environment; for other equipment the applicable test points are 134.2 kHz and 13.56 MHz.

Our device has built-in NFC or RFID. Is a communication dropout a failure?

The amendment accepts that equipment with radio functions may not communicate when tested within its passband, but basic safety and essential performance must be maintained. Whether a dropout is acceptable depends on whether the link carries essential performance and on the criteria defined beforehand.

Is the test required for registration in China?

YY 9706.102-2021 is a modified adoption of IEC 60601-1-2:2007 and contains no proximity magnetic field test. Whether a product needs a separate evaluation for Chinese registration is best confirmed with the reviewing authority or the registration testing institution.

What accreditation does a SUNGO report for this test carry?

It is issued by the Hefei laboratory of Hefei SUNGO Medical Technology Co., Ltd., with the standards in the scope table within its IAS accreditation scope (TL-1119); the edition is confirmed when the order is accepted. Acceptance by a particular regulator depends on that regulator's requirements.

Requesting a quote

For a quote or a check of your standards list, see our EMC testing service page, then use the contact page to send the product name and models, target markets, standard numbers and editions, intended use environment and a note on where the magnetically sensitive parts are. We will check each standard against the Hefei laboratory's IAS accreditation scope (TL-1119) and then propose a test plan.