Electromagnetic compatibility testing in EMC lab
EN 61000–4–6:2014 Electromagnetic compatibility (EMC) — Part 4 – 6: Testing and measurement techniques — Immunity to conducted disturbances, induced by radio-frequency fields (IEC 61000 – 4-6:2013)
Analog: IEC 61000 – 4-6:2013 Electromagnetic compatibility (EMC) — Part 4 – 6: Testing and measurement techniques — Immunity to conducted disturbances, induced by radio-frequency fields
Replace: EN 61000 – 4-6:2009 Electromagnetic compatibility (EMC) — Part 4 – 6: Testing and measurement techniques — Immunity to conducted disturbances, induced by radio-frequency fields
New in this edition:
• Updates in CDN usage;
• Calibration of clamps;
• Reorganized clause 7 regarding test setup and injection methods;
• Annex A is dedicated to EM and decoupling clamps;
• Annex G which now addresses the measurement uncertainty of the voltage test level;
International standard EN 61000 – 4-6:2014 relates to conducted immunity requirements of electrical and electronic equipment to electromagnetic disturbances created by RF transmitters in frequency range 150kHz-80MHz. This standard is not applicable to equipment have no wires (power supply cables, grounding cables, signal, telecommunication cables etc.).
Electronic activity in radio frequencies in any equipment creates electromagnetic field. When wires and cables are exposed to these fields, currents and voltages are created in these conductors. Radio, TV, radar, smartphones etc. use radio frequency energy to perform their functions, therefore emit high power fields. These fields can be conducted through cables to other equipment or radiated in air and induced in cables. Current test method verifies equipment susceptibility to high power electromagnetic fields induced in cables. These disturbing fields are approximated by electric and magnetic near-fields. Disturbances are induced in cables directly using coupling decoupling devices. Disturbances are induced in common mode regarding ground reference plane. Cable systems connected to an equipment are assumed to be in resonant mode (λ/4, λ/2 open or folded dipoles) and as such are represented by coupling and decoupling devices having a common mode impedance of 150Ω with respect to a reference ground plane. Where possible the EUT is tested by connecting it between two 150Ω common mode impedance connections: one providing an RF source and the other providing a return path for the current.
International standard EN 61000 – 4-6:2014 define following immunity levels in frequency range 150kHz-80MHz. Test levels are expressed in RMS values.
During immunity tests these signal is 80% amplitude modulated using 1kHz sine wave to simulate actual threats. Example of amplitude modulation is shown below.
Test levels must be selected according to specific product standards or generic standards that defines levels in accordance to electromagnetic environment. For equipment intended to be operated in a wide range of environments following classification can be used:
Class 1: Low level electromagnetic environment. Typical environment next to low power transceivers and environments at least 1km far away from radio and television transmitters.
Class 2: Moderate electromagnetic environment. Typical environment next to portable transmitters with power less than 1W. Typical household and commercial environment.
Class 3: Severe electromagnetic environment. Typical environment where transmitters with power less than 2W are in use in close proximity. High power broadcast transmitters and ISM equipment are in close proximity. Typical industrial environment.
Disturbances are injected using coupling decoupling devices. These devices couple signal to cable with low insertion loss and decouple disturbance from auxiliary equipment. Both devices can be integrated in one enclosure. Preferred device is CDN– coupling decoupling network. Also current clamp can be used and electromagnetic clamp can be used with appropriate decoupling network.
Disturbances shall be injected in all cables connected to equipment under test. In current case (upper picture) EUT has two cables ant two auxiliary equipment. In first cable CDN is used for disturbance injection between EUT and auxiliary equipment. In second cable injection clamp is used.
During the testing only one cable at a time is tested. The frequency range is swept from 150kHz to 80MHz, using the signal levels established during the setting process, and with the disturbance signal 80% amplitude modulated with a 1kHz sine wave, pausing to adjust the RF signal level or to change coupling devices as necessary. Where the frequency is swept incrementally, the step size shall not exceed 1% of the preceding frequency value. The dwell time of the amplitude modulated carrier at each frequency shall not be less than the time necessary for the EUT to be exercised and to respond, but shall in no case be less than 0,5s. The sensitive frequencies (e.g. clock frequencies or frequencies identified by the manufacturer or obtained as outcome of the test) shall be analysed in addition to the stepped frequencies.
Attempts should be made to fully exercise the EUT during testing, and to fully interrogate all exercise modes selected for susceptibility.
The use of a special exercising program is recommended.
The tests results are classified in terms of loss of function or degradation of performance. International standard EN 61000 – 4-6:2014 does not define Pass/Fail criteria. This is defined by generic or specific product standards. EN 61000 – 4-6:2014 defines performance criteria that can be used to evaluate equipment under test performance.
Performance criterion A
Normal performance within limits specified by the manufacturer;
Performance criterion B
Temporary loss of function or degradation of performance. Self-recovery after the test, without operator intervention;
Performance criterion C
Temporary loss of function or degradation of performance. Operator intervention needed for recovery after the test;
Performance criterion D
Loss of function or degradation of performance which is not recoverable. Damage
of hardware or software, or loss of data.
The manufacturer’s specification may define effects on the EUT which may be considered insignificant, and therefore acceptable.