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Track 13: EMI/EMC Compliance Testing

A comprehensive guide to EMC emissions and immunity testing per international standards. Learn about test setups, procedures, limits, and the equipment used in compliance laboratories.

1. Conducted Emissions Testing

Conducted emissions (CE) measure the noise your product injects back onto the AC mains power line. Testing uses a Line Impedance Stabilization Network (LISN) to provide a defined impedance and couple the noise to the measurement receiver.

LISN Conducted Emissions Setup AC Mains LISN 50\u03A9/50\u00B5H per CISPR 16 EUT Device Under Test L N Receiver EMI / SA 50\u03A9 CE noise Ground Reference Plane (2m x 2m)

Standard

CISPR 32 / EN 55032 (multimedia), CISPR 11 / EN 55011 (ISM), FCC Part 15 Subpart B. Frequency range: 150 kHz to 30 MHz.

Procedure

  1. Connect EUT to LISN on 80cm non-conductive table
  2. Measure Line (L) and Neutral (N) separately
  3. Use quasi-peak and average detectors
  4. Scan 150 kHz to 30 MHz
  5. Compare against Class A or Class B limits
  6. Record worst-case operating mode

CISPR Conducted Emission Limits

Frequency Range Class A QP (dBμV) Class A Avg (dBμV) Class B QP (dBμV) Class B Avg (dBμV)
150 kHz - 500 kHz796666-56*56-46*
500 kHz - 5 MHz73605646
5 MHz - 30 MHz73606050

* Class B limit decreases linearly with log frequency in the 150-500 kHz band.

Interactive Conducted Emissions Spectrum

55 dBμV
200 kHz
Adjust parameters to see the conducted emissions spectrum with CISPR limit overlay.

2. Radiated Emissions Testing

Anechoic Chamber / OATS EUT 360\u00B0 rotation 3m or 10m Antenna 1-4m height Receiver

Standard

CISPR 32, FCC Part 15 Subpart B, EN 55032. Frequency range: 30 MHz to 1 GHz (6 GHz for some standards). Measured at 3m (CISPR) or 10m (FCC/CISPR) distance.

Procedure

  1. Place EUT on turntable at 80cm height in chamber
  2. Antenna scans 1m to 4m height for maximum
  3. Rotate turntable 360 degrees for each frequency
  4. Measure horizontal and vertical polarization
  5. Scan 30 MHz to 1 GHz (or 6 GHz)
  6. Record peak, quasi-peak, and average values
Frequency Range Class A @ 10m (dBμV/m) Class B @ 10m (dBμV/m) Class B @ 3m (dBμV/m)
30 MHz - 230 MHz403040
230 MHz - 1 GHz473747

3. ESD Immunity (IEC 61000-4-2)

ESD Gun (IEC 61000-4-2) EUT ESD Gun 150pF + 330\u03A9 \u26A1 Charged Ground Reference Plane GND strap

Description

Simulates electrostatic discharge from a human body (150 pF charged through 330 ohm). Tests both contact discharge (applied directly to conductive surfaces) and air discharge (approached until spark occurs).

Rise Time

Sub-nanosecond rise time (0.7 - 1 ns) with peak currents up to 30A at Level 4. The fast transient has spectral content extending into GHz range.

ESD Test Levels (IEC 61000-4-2)

LevelContact Discharge (kV)Air Discharge (kV)Peak Current (A)
1227.5
24415
36822.5
481530
X (special)User-definedUser-definedVaries

4. Electrical Fast Transient (EFT) / Burst (IEC 61000-4-4)

EFT Burst Waveform 15ms burst 300ms period Single pulse: 5ns rise / 50ns duration Repetition: 5 kHz or 100 kHz

Description

Simulates fast transient bursts caused by relay switching, contactor operations, and switching of inductive loads. Applied to power supply ports and signal/control ports via capacitive coupling clamp.

Key Parameters

Rise time: 5 ns. Pulse duration: 50 ns. Repetition rate: 5 kHz (power) or 100 kHz (signal). Burst duration: 15 ms. Burst period: 300 ms. Applied for 1 minute per polarity.

LevelPower Ports (kV)Signal Ports (kV)Repetition Rate
10.50.255 / 100 kHz
21.00.55 / 100 kHz
32.01.05 / 100 kHz
44.02.05 / 100 kHz

5. Surge Immunity (IEC 61000-4-5)

Combination Wave Surge Open-circuit: 1.2/50 \u00B5s 1.2\u00B5s 50\u00B5s Short-circuit: 8/20 \u00B5s 8\u00B5s 20\u00B5s MOV Clamp TVS Diode GDT Spark Gap

Description

Simulates high-energy surges from lightning indirect effects, power line switching, and fault conditions. Uses a combination wave generator producing 1.2/50 us open-circuit voltage and 8/20 us short-circuit current simultaneously.

Protection Strategy

Multi-stage protection: GDT (primary, high energy) -> MOV (secondary, clamping) -> TVS diode (fine protection, fast). Coordination between stages is critical to ensure each device handles appropriate energy level.

LevelLine-to-Line (kV)Line-to-Ground (kV)Generator Impedance
10.50.52\u03A9 (L-L), 12\u03A9 (L-G)
21.01.02\u03A9 / 12\u03A9
32.02.02\u03A9 / 12\u03A9
44.04.02\u03A9 / 12\u03A9

6. Conducted RF Immunity (IEC 61000-4-6)

CDN Injection Setup RF Gen 150k-230MHz Amp CDN Coupling/ Decoupling EUT AE Port Ground Reference Plane 80% AM, 1kHz

Description

Simulates RF fields coupled onto cables and interconnects. Uses CDNs (Coupling/Decoupling Networks) or EM-clamp to inject 80% AM-modulated RF onto power and signal cables. Range: 150 kHz to 80 MHz (or 230 MHz).

Test Levels

Level 1: 1 V rms | Level 2: 3 V rms | Level 3: 10 V rms | Level 4: 30 V rms. Applied as unmodulated voltage, 80% AM at 1 kHz. Dwell time: typically 3 seconds per frequency step.

7. Radiated RF Immunity (IEC 61000-4-3)

Radiated Immunity Chamber TX Antenna Uniform Field Area 1.5m x 1.5m EUT 3m distance probe

Description

EUT is exposed to a uniform electromagnetic field (80 MHz to 1 GHz, extendable to 6 GHz). The field is 80% AM modulated at 1 kHz. A field uniformity calibration ensures +/-6 dB uniformity over 75% of the test area.

Test Levels

Level 1: 1 V/m | Level 2: 3 V/m | Level 3: 10 V/m | Level 4: 30 V/m. Automotive often requires 100-200 V/m. Forward power is adjusted during test to maintain constant field strength.

8. EMC Test Equipment

LISN (Line Impedance Stabilization Network)

Provides defined 50 ohm/50 uH impedance for conducted emissions measurement per CISPR 16. Isolates EUT from mains noise. Also called AMN (Artificial Mains Network). Handles up to 16A or 50A for high-power units.

Anechoic Chamber

Shielded room lined with RF-absorbing material (ferrite tiles + foam absorbers). Provides a controlled environment free from ambient RF noise. Semi-anechoic chambers have a reflective ground plane. Fully anechoic chambers absorb all walls.

EMI Test Receiver

Specialized receiver per CISPR 16-1-1 with peak, quasi-peak, average, and RMS detectors. Calibrated bandwidths: 200 Hz (band A), 9 kHz (band B), 120 kHz (band C/D). More accurate than spectrum analyzers for compliance.

Spectrum Analyzer

Used for pre-compliance and diagnostic measurements. Faster sweep than EMI receivers. Modern analyzers include time-domain scan (real-time) capability. Must apply correction factors for compliance-grade measurements.

Near-Field Probes

H-field (loop) and E-field (monopole) probes for localizing EMI sources on PCBs. Essential for debugging. Resolution depends on probe tip size. Used with spectrum analyzer for relative measurements.

Current Probes

Clamp-on probes to measure common-mode and differential-mode currents on cables. Transfer impedance specified in dB-ohms. Frequency range typically 10 kHz to 1 GHz. Essential for cable emission diagnostics.

Antennas

Biconical (30-300 MHz), log-periodic (200 MHz-2 GHz), horn (>1 GHz), bilog (broadband 30 MHz-3 GHz). Each has calibrated antenna factors for converting received voltage to field strength.

ESD / Surge / EFT Generators

Specialized pulse generators per IEC 61000-4-x standards. ESD gun (4-2), burst/EFT generator (4-4), combination wave surge generator (4-5). Must be calibrated annually per standard requirements.

9. Standards Comparison: IEC / CISPR / FCC

Different regulatory bodies and standards organizations have overlapping but distinct requirements. This table summarizes key differences.

Aspect CISPR / IEC (EU - CE Mark) FCC (USA) VCCI (Japan)
Conducted Emissions CISPR 32 / EN 55032, 150 kHz - 30 MHz, QP + Avg FCC Part 15B, 150 kHz - 30 MHz, QP VCCI V-3, aligned with CISPR 32
Radiated Emissions CISPR 32, 30 MHz - 1 GHz (6 GHz), 10m or 3m FCC Part 15B, 30 MHz - 40 GHz, 3m/10m VCCI V-3, 30 MHz - 1 GHz, 10m
Immunity (ESD) IEC 61000-4-2, mandatory for CE Not required by FCC Not required by VCCI
Immunity (EFT) IEC 61000-4-4, mandatory for CE Not required Not required
Immunity (Surge) IEC 61000-4-5, mandatory for CE Not required Not required
Immunity (CI/RI) IEC 61000-4-3 / 4-6, mandatory Not required Not required
Classes Class A (commercial), Class B (residential) Class A (commercial), Class B (residential) Class A / Class B
Certification Self-declaration (DoC) with test report Supplier's DoC (SDoC) or certification Self-declaration (voluntary)
Key Difference Full emissions + immunity required Emissions only, no immunity Voluntary, emissions only

Note on Harmonization

CISPR standards are developed by the IEC and adopted (with modifications) by regional bodies. The EU references CISPR via EN harmonized standards. FCC limits are generally similar to CISPR Class B at 10m, but detector requirements and frequency ranges may differ. Always verify the specific standard applicable to your product and target market.

Track 13 Quiz: EMC Compliance Testing

1. What is the purpose of a LISN in conducted emissions testing?

The LISN provides a standardized 50 ohm/50 uH impedance at the EUT power port, isolates from mains noise, and couples the EUT's conducted emissions to the measurement receiver.

2. Conducted emissions testing covers which frequency range?

Conducted emissions are measured from 150 kHz to 30 MHz. Above 30 MHz, radiated emissions testing takes over, as noise tends to radiate rather than conduct at higher frequencies.

3. In ESD testing per IEC 61000-4-2, Level 4 contact discharge is:

IEC 61000-4-2 Level 4 contact discharge is 8 kV (air discharge is 15 kV). The corresponding peak current is approximately 30 A.

4. The EFT burst test (IEC 61000-4-4) simulates:

EFT/Burst testing simulates the fast, repetitive transients generated by switching of inductive loads, relays, and contactors. Individual pulses have 5 ns rise time and 50 ns duration.

5. The surge test waveform (IEC 61000-4-5) combination wave consists of:

The combination wave generator produces a 1.2/50 us open-circuit voltage waveform and an 8/20 us short-circuit current waveform. This simulates lightning indirect effects and power switching surges.

6. Which major difference exists between EU (CE marking) and FCC requirements?

The EU CE marking requires both emissions testing (EN 55032) and immunity testing (EN 55035 referencing IEC 61000-4-x). FCC Part 15 only requires emissions testing with no immunity requirements.

7. For radiated emissions, what is the CISPR Class B limit at 30-230 MHz measured at 10m?

CISPR Class B (residential) limit for 30-230 MHz at 10m distance is 30 dBuV/m. Class A (commercial) is 40 dBuV/m at the same distance. At 3m, add approximately 10 dB.

8. What is the purpose of field uniformity calibration in radiated immunity testing?

Field uniformity calibration ensures that at least 75% of the 16 measurement points in the 1.5m x 1.5m test area have field strength within +6 dB of the nominal level, providing repeatable test conditions.