Three important rules of electrostatic discharge generator EMC
1. Law of EMC cost-effectiveness relationship: the earlier EMC problems are considered and solved, the lower the cost and the better the effect.
EMC design can be carried out in the development stage of new products, which can save the cost and improve the efficiency greatly compared with the improvement after the product EMC test fails.On the contrary, the efficiency will be greatly reduced and the cost will be greatly increased.
2. The larger the area of high-frequency current loop S is, the more serious EMI radiation is.
High frequency signal current flows through the inductance minimum path.When the frequency is higher, the general line reactance is greater than the resistance, the connection to the high-frequency signal is the inductance, series inductance caused by radiation. Most of the electromagnetic radiation is generated by high-frequency current loops on EUT's devices, the worst of which is the form of an open antenna. The corresponding treatment method is to reduce or shorten the connection line, reduce the area of high-frequency current circuit, and eliminate any antenna needed for abnormal work, such as discontinuous wiring or excessively long pins of components with antenna effect.
3. The higher the loop current frequency f is, the more serious the EMI radiation is caused, and the electromagnetic radiation field intensity increases in proportion to the square of the current frequency f.One of the most important ways to reduce the radiation disturbance or improve the anti-interference ability of radio frequency radiation is to try every means to reduce the high-frequency current frequency f of the disturbance source, that is, to reduce the frequency f of the disturbance electromagnetic wave.
Indirect discharge test of discharge generator
According to the standard, the indirect discharge test in contact discharge should be carried out when the electrostatic discharge generator discharges. Specifically, a horizontal coupling board is laid on the test table, and a vertical coupling board is set on the side at the same time. Then discharge the horizontal and vertical coupling board with the electrostatic gun to see whether the equipment is affected or not.
According to the standard, both the horizontal and vertical coupling plates are grounded by two 470K resistances, and the two resistances are distributed at both ends of the grounding wire, which leads to the following problem:
1. What's the function of the two resistors?
2. Why use 2 470K resistors?
3. Why are the two resistors at both ends of the ground wire?
As you may know, the first problem is that the discharge of the horizontal and vertical coupled plates affects the equipment through transient electromagnetic fields and static electric fields. Therefore, the two resistances are designed to prevent the rapid discharge of static charges along the ground, and the electrostatic field cannot be generated.In addition, high impedances tend to accumulate charges, which eventually accumulate until these resistances are released.
The second problem is that the resistance of the human body to the ground is about 1M, and the resistance of the two 470K is exactly the same.
The third problem is to put the two resistances on opposite ends. Because the impedance does not match, the current generated by the static charge bounces back and forth between the two resistances until it disappears, reducing the current flowing to the ground.
This test is mainly to simulate the discharge of human body to other objects at the side of the tested equipment, and indirectly to test whether the tested equipment is affected.
Electrostatic discharge generator: characteristics of electromagnetic disturbance
Through the previous text we know what is electromagnetic harassment, today electrostatic discharge generator manufacturers Zhengzhou Defy with you to look at the characteristics of electromagnetic harassment.
Through the introduction of electrostatic discharge generator manufacturers, EMC problems will be regulated, adhere to the EMC rules to solve EMC problems save time and effort, get twice the result with half the effort.