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EMI Test
Resource:Chengdu MengSheng Electronics Co., Ltd       Pubic Date:2017-01-15   Hits:2181

Instructions on EMI testing

Electro magnetic Interference (simplified as EMI), it refers to the interference phenomenon after electromagnetic wave acting on electronic component, and it includes conducted interference and radiated interference. Conducted interference refers to the coupling (interference) of a signal on an electrical network to another electrical network through a conductive medium. Radiation interference refers to the coupling (interference) of the signal of certain interference source to another electrical network via space. In high speed PCB and system design, high frequency signal line, integrated circuit pin and all kinds of connectors may become the radiation interference source with antenna characteristics, all can emit electromagnetic waves and affect the normal operation of other systems or other subsystems within the system.

Contents of EMI testing

The so-called interference refers to performance degradation after device interference and interference source for equipment interference. The first layer means that the thunder makes the radio noise, there is snow on the TV after the motorcycle is driving nearby, and hearing the radio sound after picking up phones, etc., these can be referred to as "BCI", "TVI", "TelI", these abbreviations all have the same "I" (interference).

So what are the EMI standards and EMI testing parts of the EMI? Of course, its second meaning, that is, the source of interference, including the electromagnetic energy before interference.

Followed by "electromagnetic”. If the charge is stationary, it is called electrostatic. Electrostatic discharge occurs when the potential moves towards the same direction, there will be current, and magnetic field is thus generated around current. If the direction and size of the current continues to change, electromagnetic waves are generated.

Electricity exists in a variety of States, and we call all of these states electromagnetic. So the EMI standard and the EMI test determine the state of the electricity to be processed, determine how to detect, and how to evaluate it.

Relevant requirements on EMI testing

In todays economic globalization, most international markets are required to provide EMC emission compliance certification; At present, the European Union is the only major market that also needs immunity (EMI) certification. Products that to be sold in the European market must comply with the EN and IEC standards for EMC immunity performance.

Electrostatic discharge

+/-15kV contact discharge, +/-30kV air discharge

A laboratory with temperature and humidity controlled

Electrostatic target, 1GHz oscilloscope

The standard IEC/EN test and various electrostatic discharge heads for the automotive industry are also presented.

Big current injection (BCI)

Forward, reverse, and net power measurements are performed in each test using a bidirectional power meter and a probe

Specially designed equipment for improving repeatability precision

Specific devices that meet test standards (designed to ensure correct testing and repeatability)

Testing in accordance with Ford, GM, Chrysler, Fiat, Honda, Nissan, Mazda, Audi, ISO or any other BCI standard

Radiation electromagnetic field (RF)

Uniform magnetic field in accordance with IEC/EN code

Modulation type (AM, FM, pulse)

The field strength is designed for >600V/m, ranging from 1mCW or pulse 1 to 18GHz

Provide calibration sites with maximum 18GHz

1kW amplifier, 80MHz to 1GHz

250W amplifier, 1GHz to 18GHz

500W amplifier, 10kHz to 200MH

5MEMC Lab - capable of testing 26MHz to 18GHz. Testing according to the following criteria: SAE, ISO, GM, Ford, Chrysler, Audi, Nissan, Honda, Mazda, Fiat, CISPR25; 11, 16, 22, SAEJ1113, SAEJ551.

General industry standards, including automotive, general 5097, 3100, DC10614REVA, AB/AC, Ford, Nissan, Mazda, Fiat, Honda, Audi, Chrysler, Mazda, SAE, ISO, Mazda.

Provide peripheral support tools: compressed air, oiled or purified 2 microns, water (maximum 100PSI), external outlet (200CFM), AC power - maximum (50 or 60Hz) single-phase or three-phase, DC power supply - maximum. Full color internal monitoring system provides multiple camera angles, as well as generators, coolers, power loads, inert gas, EMC computers.

EUT (test equipment) can be desktop or floor mounted equipment.

Range of EMI testing

Range: EN standard IEC standard

Electrical fast transient pulse group immunity EN61000-4-4IEC801-4; IEC61000-4-4

Conducted continuous interference 150kHz from DC to EN61000-4-16IEC61000-4-16

Radio frequency field induced conduction interference EN61000-4-6IEC61000-4-6

Electrostatic discharge EN61000-4-2IEC61000-4-2

General immunity - industrial environment EN61000-6-2IEC61000-6-2

General immunity - residential, commercial and light industry EN61000-6-1IEC61000-6-1

Magnetic field and damped shock wave EN61000-4-10IEC61000-4-10

Magnetic field and ringing wave EN61000-4-12IEC61000-4-12

Power frequency magnetic field EN61000-4-8IEC61000-4-8

Pulsed magnetic field EN61000-4-9IEC61000-4-9

Pulsed magnetic field EN61000-4-3IEC61000-4-3

Surge EN61000-4-5EN61000-4-5

Voltage sags, short interruptions and voltage variations EN61000-4-11IEC61000-4-11

How to pass EMI testing

Check whether the screw at the end of the cable is locked, tighten the screws and the shielding effect of cable can be strengthened. Also check to see if the grounding of the Connector outside the machine is good, if the shell is metal and sprayed with paint, we can shave off the paint at Connector to make the grounding effect more better. In addition, if the Shielded cable is used, it is required to check whether the metal alloy covered at the end of joint fits with the metal cover, many of the poor shielding wires (RS232) are shielded by the outer covering of the metal wires and the connecting ends of the wire joints, so that it cant get enough shielding effect.

Various joints, such as Keyboard and Powersupply often affect the radiation of interference noise due to poor adaptation of the plug of the connector and the socket on the machine. The way to check is to unplug the joint to see if the noise is reduced, if there is reduction, it means, firstly, radiation interference on the line itself, secondly, poor contact between joints. At this point, plug in the connector, use hand to shake the joint end, see if the noise will decrease or disappear, if it decreases, tape connectors for Keyboard or Powersupply with copper foil tape, so as to increase the tightness of the machine and its joints. This is also very easy to be overlooked in actual measurement, then, there will be erroneous judgement on why does the EMI of the machine perform bad, or spend a lot of time on other countermeasures.

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