Research on Common Mode Inductor Balance Tester for Ls and DCR Balance Measurement of Common Mode Inductors and Filter Common Mode Inductors

Abstract

This paper focuses on the application of Common Mode Inductor Balance Tester in the balance measurement of inductance (Ls) and direct current resistance (DCR) for common mode inductors and filter common mode inductors. Taking the LISUN LS8517CX Common Mode Inductor Balance Tester as a core case, the article elaborates on the technical principles, measurement accuracy, functional characteristics, and model differences of this testing equipment. It also provides detailed comparative data through tables to illustrate the performance advantages of different models in various testing scenarios, aiming to offer a comprehensive reference for production line quality control, incoming material inspection, and component design and evaluation in the electronics industry.

1. Introduction
Common mode inductors and filter common mode inductors are critical components in electronic circuits, playing a vital role in suppressing electromagnetic interference (EMI) and ensuring signal integrity. The balance of inductance (Ls) and direct current resistance (DCR) are key parameters affecting their performance. Improper balance can lead to unbalanced filtering effects, increased power loss, and even circuit malfunctions. Therefore, precise measurement of these parameters is essential for maintaining product quality and reliability.

The Common Mode Inductor Balance Tester, also known as a filter balance tester, is specialized equipment designed to address these measurement needs. This paper introduces the technical specifications and application scenarios of the LISUN LS8517CX series, highlighting how this equipment meets the rigorous requirements of modern electronics manufacturing through high-precision testing and flexible automation integration capabilities.

2. Technical Principles of Common Mode Inductor Balance Tester

2.1 Basic Measurement Principles

The balance tester operates based on the principle of electrical impedance analysis. For common mode inductors, it measures the inductance (Ls) by applying an alternating current (AC) signal at specific frequencies and analyzing the phase shift and amplitude change of the voltage and current. The DCR is measured using a direct current (DC) source to calculate the resistance value through Ohm’s law. The “balance” here refers to the consistency of parameters between multiple windings or components, which is critical for multi-winding inductors and filter modules.

2.2 Key Technical Features of LISUN LS8517CX

High Precision: The equipment achieves a basic measurement accuracy of up to 0.1%, with some models (e.g., LS1085CX) reaching 0.05%, ensuring reliable data for critical component evaluation.
Wide Frequency Range: Capable of testing from 50Hz to 200kHz, covering the frequency bands required for most common mode inductors in low-frequency and high-frequency applications.
Multi-Parameter Testing: Besides Ls and DCR, it can measure other parameters such as quality factor (Q), impedance (|Z|), phase angle (θ), and dissipation factor (D), providing a comprehensive assessment of component performance.

Automation Integration: Equipped with diverse communication interfaces (RS232C, USB, Handler), it enables seamless connection with automated production lines, improving testing efficiency and reducing manual errors.

3. Model-Specific Applications

• LS7575BN: Maximum frequency 10KHz, 4.3 “LCD 2U standard case
• LS1085CX: Test frequency 50-200kHz, DCR test function, standard test box, balance fixture
• LS8517CX-4PA: 2 pairs of winding test with frequency 50-200kHz, can simultaneously test Ls, DCR, cycle ratio, balance function
• LS8517CX-6PA: 3 pairs of winding test with frequency 50-200kHz, can simultaneously test Ls, DCR, cycle ratio, balance function

LS8517CX Common Mode Inductor Balance Tester

4. Application Scenarios of Common Mode Inductor Balance Tester

4.1 Production Line Quality Assurance

In mass production, the balance tester is integrated into automated production lines to perform 100% inline testing of common mode inductors. For example, in the manufacturing of switching power supplies, the LS8517CX can quickly measure Ls and DCR of filter inductors at high test speeds (e.g., 50 times/s for LS1085CX), ensuring that each component meets design specifications before assembly. The comparator function (PASS/FAIL/BIN classification) enables real-time quality screening, reducing defective product rates.

4.2 Incoming Material Inspection

Component suppliers and electronics manufacturers use the tester to verify the quality of incoming common mode inductors. By testing parameters against supplier datasheets, inconsistencies in Ls or DCR caused by material variations or manufacturing defects can be identified. For instance, a DCR deviation exceeding 5% may indicate poor winding soldering or wire gauge issues, which can be flagged early through precise measurements.

4.3 Component Design and R&D

During the design phase, engineers rely on the tester’s high-precision data to optimize inductor structures. For example, when developing a high-frequency filter inductor, the LS1085CX’s 200kHz test capability allows engineers to analyze inductance stability at high frequencies, while the phase angle (θ) measurement helps evaluate the reactive and resistive components of the inductor. The ability to store and recall multiple test groups (50 internal, 500 external via USB) facilitates comparative analysis of different design prototypes.

5. Advantages of LISUN LS8517CX Series

5.1 High Precision and Stability

The 0.1% basic accuracy (0.05% for LS1085CX) ensures reliable measurements even for small inductors (down to 0.0001μH) or low-resistance DCR (0.01mΩ). This is particularly important for high-density circuit boards where component miniaturization requires ultra-precise parameter control.

5.2 Versatility and Scalability

With support for multiple test frequencies, impedance ranges, and winding configurations, the series can adapt to diverse industry needs. For example, the LS8517CX-6PA’s three-pair winding test is indispensable for testing multi-phase inductors used in electric vehicles or renewable energy systems.

5.3 User-Friendly Interface and Automation

The 4.3-inch LCD display (LS7575BN) and intuitive menu system simplify operation, while advanced trigger modes (e.g., bus control) enable seamless integration with robotic arms or conveyor systems in smart factories. The ability to export test data to USB drives supports traceability and quality management systems.

6. Challenges and Future Trends

While current common mode inductor balance testers offer high performance, challenges remain in testing ultra-high-frequency inductors (e.g., above 1GHz) and components with nanoscale structures. Future developments may focus on:
Extending frequency ranges to accommodate next-generation wireless and radar applications.
Integrating AI algorithms for real-time defect prediction and measurement optimization.
Enhancing portability for on-site testing in remote or harsh environments.

7. Conclusion

The Common Mode Inductor Balance Tester, represented by the LISUN LS8517CX series, is an indispensable tool for ensuring the quality and performance of common mode inductors and filter components. Its high precision, wide frequency coverage, and automation capabilities make it suitable for all stages of the product lifecycle, from R&D to mass production. By providing detailed parameter measurements and balance analysis, this equipment helps manufacturers meet increasingly stringent electromagnetic compatibility (EMC) standards and drive innovation in the electronics industry.