EMC test is the electromagnetic compatibility test, mainly for electronic products. Due to different type of work products,different external radiation, different sensitivity of the electromagnetic frequency, a variety of different organizations, such as the FCC or EN will classify electronic products, such as ism, electric tools, computer information technology, etc.,according to different standard test, after find the products’test standards, in accordance with the standard test methods and test requirements to pay attention to the test items. Although the different countries had the same test methods and requirements, but also remains differences, respectively, depends on where the product export.

Understanding the EMC test, you need to care the device in the EMC test, let's see it emphatically from below aspects.

1# On the antenna

EMC test frequency range generally becomes more broad, because the original is not clear how often harassed, so the test must use all kinds of detecting antenna to the field strength convert into voltage. In general, EMC test antenna are working in near-zone, test results of the test is very sensitive. Because the ratio of the electric field, magnetic field (wave impedance) in near-zone is no longer a constant, so although these antenna shows the correction coefficient of electric field, magnetic field, but only when these antenna far field test is valid, measuring the nearfield interference, electric field and magnetic field test result can't be in this conversion.

2# The artificial network

Pay attention to the artificial network and good grounding plate into a low impedance connection.

Spectrum analyzer
Choose a spectrum analyzer has a lot of exquisite, should pay special attention to the requirement of the test to select dynamic range, the frequency resolution, sensitivity, frequency sweep width parameters.The frequency resolution: to line interval, it represents the spectrum analyzer to be cuddled up together frequency signal of the ability to distinguish.

Sensitivity
characterization of a spectrum analyzer to measure the ability of small signal. Spectrum analyzer noise level decision used filter bandwidth, is in commonly - 80 db ~ - 130 db.

3# Signal dynamic range

Characterize the true spectrum of the small signal ability, dynamic range of the upper limit is determined by the nonlinear distortion of the spectrum analyzer. Spectrum analyzer dynamic range generally in more than 60 db, or even 100 db.Frequency sweep width: spectrum analyzer in the process of a measurement analysis show that the range of frequencies.

4# The measuring receiver

If the spectrum analyzer has peak detection only, the measuring receiver except for peak detection,also has quasi-peak detector and average detection, we have to according to the different standards or regulations, select the appropriate detector.Peak detection tests the maximum of disturbance signal amplitude only, suitable for single pulse or low pulse repetition frequency disturbance signal test. And some disturbance signal encreases as the effection of audio repetition frequency increases, the signal measuring signal amplitude can not only reflect the effect if only test the amplitude, therefore, would then use quasi-peak detector.

Quasi peak detector of the charging time constant is bigger than peak detector, the discharge time constant is smaller than peak detector, not only measure the signal amplitude disturbance signal, also reflect the distribution of time.