Rectification skills and precautions for EMC electromagnetic compatibility testing

Date：2022-12-08 14:51:00Views：475

The full name of EMC test (electromagnetic compatibility test) is Electro Magnetic Compatibility, which is defined as the ability of equipment and systems to work normally in their electromagnetic environment without causing unbearable electromagnetic interference to anything in the environment. Therefore, the EMC test includes two requirements: on the one hand, the electromagnetic interference generated by the equipment to the environment during normal operation cannot exceed a certain limit; On the other hand, it means that the appliance has a certain degree of immunity to electromagnetic interference existing in the environment, that is, electromagnetic sensitivity.

Rectification techniques for adding magnetic ring in EMC test of electromagnetic compatibility are as follows:

1. Put the magnetic ring through the connecting line and inject it outside.

2. Wrap the connecting line in the anti-interference magnetic ring for several times, which can both fix and increase the anti-interference effect of the line.

3. The buckle type magnetic ring is conveniently clamped on the power line and signal line. Flexible, reusable installation. It has its own card type fixation, which does not affect the overall image of the equipment.

4. The magnetic ring "as long, as thick as possible, and as small as possible in inner diameter" shall be selected for appearance. That is, the longer the magnetic ring is, the better, and the closer the aperture is to the cable it passes through, the better. However, in the case of DC or AC bias, there is also the problem of ferrite saturation. The larger the cross-sectional area of the suppression element, the more difficult it is to saturate.

5. The magnetic ring can conditionally reflect the electromagnetic wave, thus reducing the distortion of signal transmission. The position of the magnetic ring sleeve should be as close as possible to the end of the source (the inlet and outlet of the cable), which will more effectively suppress electromagnetic radiation.

6. Nickel zinc ferrite should be used to suppress high-frequency interference, and manganese zinc ferrite should be used to suppress low-frequency interference. Because the magnetic permeability of manganese zinc ferrite is thousands to tens of thousands, while that of nickel zinc ferrite is hundreds to thousands, the higher the magnetic permeability of magnetic ring ferrite is, the greater the impedance at low frequencies is, and the smaller the impedance at high frequencies is.

7. The magnetic ring is fragile, so it needs to be well fixed during installation to avoid the magnetic ring breaking due to collision during transportation. We usually fix it with ties.

Precautions for EMC testing of electronic products:

1. Protection of electromagnetic spectrum

We only have limited electromagnetic spectrum, which can be used for radio transmission, microwave communication, X-ray machines and a large number of other products. Unfortunately, even electronic devices without transmitters emit electromagnetic radiation, just like the by-products of switching currents and voltages inherent in electronic circuits. Without limiting the amount of unexpected electromagnetic radiation from electronic products, the electromagnetic spectrum may be adversely affected, and the frequency band reserved for radio transmission may be damaged. As the number of non wireless and wireless electronic products continues to explode, the already crowded electromagnetic spectrum will become more crowded. Protecting this important resource is essential to ensure that the equipment can continue to operate normally in the future.

2. Safety

For many products and industries, EMC performance can mean the difference between life and death. Many medical, military, industrial, aerospace and automotive products (among others) have safety critical applications. If the functions of these products fail due to electromagnetic phenomena such as electromagnetic surge, ESD or radiated electric field, life will certainly be in danger. Imagine that 300 mobile phones transmit 7 watts of power on a 36000 foot airplane - a rigorous EMC test that ensures that the electrical system can withstand a variety of electromagnetic environments.

3. Product performance (quality)

The function and performance of electronic products are easily affected by external and internal EMC phenomena. For example, if the internal power regulation is too noisy, it will adversely affect sensitive analog measurements (for sensor products), or reduce the performance of radio transmitters (for wireless products). These are examples of internal EMC issues. Externally, the application of EMC will have a negative impact on products in almost unlimited ways, from data corruption to measurement accuracy, to RF performance to fried IC. EMC testing helps ensure that your equipment continues to operate as expected in a typical EMC environment, and (hopefully) reduces product returns to the level of poor EMC performance.

The above contents are about EMC EMC testing rectification skills and precautions compiled by the wound core testing team, and I hope they can help you. Our company has a team of professional engineers and industry elites, and has built three standardized laboratories with an area of more than 1800 square meters, which can undertake a variety of test projects such as electronic component test verification, IC authenticity identification, product design material selection, failure analysis, functional testing, factory incoming material inspection and tape weaving.