In order to test the electromagnetic compatibility performance of the product, it is necessary to test the harassment emission and immunity performance of the product under standardized conditions. The following are the basic characteristics of the standardized test and the reliability of the test.
Ⅰ. Standardized test
In order to reproduce test results worldwide, standardized tests should have the following three basic characteristics:
1. Consider only a certain type of electromagnetic disturbance at a certain time
2. When doing the harassment emission test, the sensitive devices and indicators used to determine the type of harassment are given. When doing the immunity test, the source and coupling network of electromagnetic harassment are specified.
3. The measurement conditions are given and standard
The electromagnetic environment of standardized test can always be controlled, so the emission level and immunity level of disturbance can be measured. The electromagnetic situation of the working environment of the device, equipment or system in the field is uncontrollable, so there are sometimes differences between the test conclusion and the actual working situation.
Ⅱ. The credibility of the test
In standardized tests, there are two important uncertain factors that affect the size of the margin between the compatibility level and the specified limit. One is the appropriateness of the test method, and the other is the dispersion of the component characteristics of the mass production equipment.
1. Appropriateness of the test method
Standardized test methods try to verify the practical conditions of almost infinite variety of equipment through a limited number of tests. In fact, the scope of application of these test methods is limited.
When carrying out standardized harassment emission test, always use the standard measurement device and the specified test equipment (measurement receiver, etc.) to connect, instead of the equipment sensitive to harassment. Similarly, in the standardized immunity test, the transmitter is a prescribed immunity tester with a prescribed coupling device, rather than an actual source of interference. Nevertheless, in order to understand the electromagnetic compatibility performance of the equipment, it is necessary to carry out such a test.
The standardized harassment emission test only considers an electromagnetic phenomenon (such as conducted emission or radiated emission) over a period of time, and the immunity test also has similar considerations. However, in the actual electromagnetic environment, all phenomena are acting simultaneously, so the standardized test method reduces the relevance to the actual electromagnetic effect.
Due to the limited applicability of standardized test methods, it is necessary to consider the margin of electromagnetic compatibility between the emission limit and the immunity limit.
2. Dispersion of component characteristics of mass production equipment
Not all devices, equipment or systems, especially those mass-produced equipment, have been tested before installation. In fact, the dispersion of component characteristics will inevitably lead to the dispersion of test data. Therefore, randomly select one from the mass-produced equipment and test whether it meets the selected limit. The result may be uncertain.
