EMI Measurement Equipment in EMC Compliance Testing of Electronic Products

Abstract: With the high-frequency and integrated development of electronic products, conducted and radiated electromagnetic interference generated by switching power supplies, motor drives and other modules continues to intensify. Electromagnetic Compatibility (EMC) has become a mandatory threshold for product launch and export certification. As core instruments to quantify interference and locate non-compliance issues, EMI measurement equipment is indispensable hardware for R&D, quality inspection departments of electronic manufacturers and third-party testing laboratories. Taking the LISUN EMI-9KB Conducted & Radiated EMI Test System as the research object, this paper illustrates the working principle and core technical parameters of this set of EMI measurement equipment. It systematically analyzes its application scenarios in three major sectors including information technology equipment, household appliances and lighting products. Through a comparison table showing performance differences among series devices, this paper demonstrates the engineering value of this EMI measurement equipment in quickly locating interference sources, supporting EMC certification and avoiding electromagnetic safety risks, providing references for enterprises in various industries to select EMC testing solutions.

Introduction

Nowadays, consumer electronics, household appliances, LED lighting and industrial power tools are widely applied. High-frequency electromagnetic noise is generated when internal switching transistors, variable frequency motors and high-speed chips operate. One type propagates through power lines and signal cables in conductive mode, disturbing power grids and surrounding equipment. The other radiates into space in the form of electromagnetic waves, resulting in abnormal phenomena such as noise on radios, flickering screens and malfunction of intelligent sensors. In severe cases, it may cause failure of electronic control systems and bring potential safety hazards.

A series of mandatory standards have been formulated at home and abroad to control electromagnetic emission, including domestic standards GB 4343.1, GB/T 9254.1, GB 17743 and international standards CISPR 14, CISPR 32, EN 55015 and FCC. Electronic products must pass conducted and radiated EMI tests to obtain 3C, CE, FCC certifications. Against this backdrop, EMI measurement equipment is in strong demand across the industry. Conventional simple spectrum analyzers feature insufficient precision and incomplete standard compatibility, failing to carry out compliance testing. As standardized professional EMI measurement equipment, the LISUN EMI-9KB Conducted & Radiated EMI Test System can complete full-range conducted emission and radiated emission tests. It accurately identifies non-compliance sources such as switching power supply noise and motor radiated interference. Widely deployed in R&D laboratories, production line sampling stations of manufacturers and third-party certification testing institutions, it greatly shortens product rectification cycles and reduces costs caused by certification failures. 

Figure: EMI tester

System Architecture and Core Performance of LISUN EMI-9KB EMI Measurement Equipment

System Composition and Structural Advantages
The complete set of LISUN EMI-9KB EMI measurement equipment consists of EMI-9KB EMI test receiver, LISN artificial mains network, isolation transformer, matched coaxial cables and PC-based testing software. Optional components such as three-loop antennas, absorbing clamps and RF current probes can be equipped to expand testing capabilities for radiation and port disturbance. The equipment adopts a fully enclosed high-conductivity alloy housing with multi-point grounding shielding structure and shielding efficiency ≥85dB. It eliminates self-generated electromagnetic interference from hardware, ensuring measured data only reflects real noise from equipment under test, and solves common industry problems including excessive self-noise and measurement distortion of ordinary testing instruments.

The system is equipped with bilingual PC software compatible with Windows 7 to Windows 11. It automatically completes frequency band scanning, spectrum curve plotting, standard limit comparison and test report export. Both fixed-point measurement and continuous scanning modes are supported. The software simultaneously acquires peak, quasi-peak and average detector data to meet mainstream global EMC testing standards.

Parameter Comparison Table of LISUN EMI-9K Series EMI Measurement Equipment
To intuitively distinguish applicable scenarios of EMI-9KB from EMI-9KA, EMI-9KBS and EMI-9KC within the same series, core specifications are sorted as follows:

As shown in the table, EMI-9KB is highly versatile EMI measurement equipment. Its 300MHz frequency range covers standard testing frequency bands for 99% of civil electronic products. Balancing testing capacity and cost, it becomes the mainstream selection for enterprise R&D laboratories and third-party testing labs.

Key Technical Indicators Supporting Accurate Interference Localization

1. Multi-range Standard Measurement Bandwidth: 200Hz bandwidth for 9kHz~150kHz, 9kHz bandwidth for 150kHz~30MHz and 120kHz bandwidth for 30MHz~300MHz, strictly complying with CISPR 16 measurement specifications to accurately capture low-frequency harmonics of switching power supplies and pulse noise of motors;

2. Three Detector Modes: Simultaneous collection of Peak (PK), Quasi-Peak (QP) and Average (AV) values. Quasi-peak detection is mandatory for certification standards and can directly generate compliance judgment data;

3. Low Noise Floor: Noise floor ≤0dBμV under peak detection from 9kHz to 30MHz. Weak interference signals will not be submerged by instrument noise floor, enabling precise localization of slightly exceeding frequency points;

4. Automatic Scanning & Diagnosis: The software automatically marks frequency points exceeding standard limits. Combined with spectrum curves, interference types can be quickly identified: continuous spikes on power lines represent common-mode noise of switching power supplies, while wideband space radiation originates from brush sparks of motors and leakage of high-speed signal lines. It provides quantitative basis for circuit filtering, housing shielding and grounding optimization.

Multi-industry Application Analysis of EMI Measurement Equipment (EMI-9KB)

Information Technology Equipment: EMC Pre-compliance Test for Chargers and Computer Peripherals
High-frequency switching inside IT products such as computers, printers, laptop power adapters, mobile fast chargers and Type-C docking stations easily causes excessive conducted disturbance. Enterprises adopt LISUN EMI-9KB EMI measurement equipment to conduct pre-tests in the R&D phase and complete rectification before submitting samples to third-party laboratories:

1. Conducted test: Extract power port disturbance voltage via LISN, locate excessive switching harmonic frequency points from 150kHz to 30MHz and guide installation of X/Y filter capacitors;

2. Radiation screening: Match three-loop antennas to test space radiation within 30~300MHz and check radiation leakage of fast-charging wireless modules;

3. Compliance benefits: Resolve interference problems in advance to avoid repeated testing caused by failed third-party

Household Appliances & Power Tools: Special Test on Motor Pulse Interference
Refrigerators, air conditioners, washing machines, electric drills, vacuum cleaners and other products are equipped with variable frequency motors and carbon brush structures. A large amount of pulsed electromagnetic interference is generated during operation, which may disturb televisions, routers and smart home central control equipment. LISUN EMI-9KB EMI measurement equipment provides a complete testing solution for such products:
Conducted item: Test power line disturbance voltage under motor start-stop and speed regulation conditions;
Radiated item: Identify high-frequency radiation from gaps of motor housing and internal driver boards;
Interference localization: Distinguish carbon brush spark interference and driver chip noise through spectrum curves, optimize magnetic rings and shielding cover design to satisfy mandatory EMC standards GB 4343.1 and CISPR 14-1 for household appliances, ensuring electromagnetic compatibility between home appliances and other consumer electronics.

Lighting Products: Radio Disturbance Test for LED Driver Power Supplies
LED lamps and moving head stage light drivers belong to non-linear loads. High-frequency noise generated during dimming easily radiates and interferes with smart switches and wireless sensors. As dedicated EMI measurement equipment, EMI-9KB fully complies with GB 17743-2022 and CISPR 15 standards for lighting products:
Low-frequency conducted test to measure driver harmonics within 9kHz~30MHz;
30~300MHz radiated test for space field strength of complete lamps;
Optional RF current probes can test disturbance current of signal lines and dimming interfaces, solving radiated interference non-compliance risks for mass-produced lamps before market launch.

Third-party Testing & Certification Laboratories: Carrier for Standardized Certification Testing
Third-party certification laboratories such as SGS, CQC and TÜV are widely equipped with LISUN EMI-9KB EMI measurement equipment to issue authoritative EMI test reports. The equipment embeds limit databases of national standards, European standards and American standards. Report formats comply with general specifications of certification bodies and can be directly applied for global market access including CE, FCC and VCCI. Moreover, the interference diagnosis function supports enterprises in completing rectification against non-compliance, expanding value-added service scope of testing institutions.

Summary of Application Value of EMI Measurement Equipment (EMI-9KB)

Quickly locate sources of excessive electromagnetic interference: For typical EMC problems including switching power supply noise, motor radiated interference and leakage of high-speed signal lines, full-band spectrum scanning accurately locks excessive frequency points and interference paths. It replaces traditional manual troubleshooting and improves rectification efficiency by over 40%;

One-stop solution for multi-standard compliance testing: Single equipment supports domestic GB standards and international emission standards including CISPR/EN/FCC, covering three mainstream industries: IT equipment, household appliances and lighting. Enterprises do not need to purchase multiple testing instruments, lowering capital investment;
Avoid equipment failures and safety risks triggered by electromagnetic interference: Screen electromagnetic noise in advance during product R&D and mass production, preventing mutual interference between devices and control system failures after launch, and minimizing losses from after-sales rework and product recalls;
Support global EMC certification of products: Standardized test data can be directly used for domestic and overseas certification, significantly improving customs clearance efficiency for exported products and helping manufacturers explore overseas markets.

Conclusion

Against the backdrop of increasingly strict EMC control in electronic industry, EMI measurement equipment serves as core testing equipment to guarantee product compliance and stable operation. Featuring wide frequency coverage from 9kHz to 300MHz, high measurement accuracy, fully automatic operation and excellent self-shielding performance, the LISUN EMI-9KB Conducted & Radiated EMI Test System acts as universal EMI measurement equipment suitable for manufacturers, R&D centers and third-party testing institutions engaged in information technology equipment, household appliances and lighting products. This equipment accurately identifies electromagnetic interference generated by switching power supplies, motors and other modules, and accelerates rectification against EMI non-compliance. It provides complete data support for EMC compliance certification, eliminates equipment malfunctions and safety hazards caused by electromagnetic interference from the source, and delivers great engineering application and industrial promotion value. As operating frequency of electronic products keeps rising, extended EMI measurement equipment such as the full 1GHz EMI-9KC will become mainstream testing instruments for high-end communication and multimedia devices.