EMC measurement vs EMI measurement-Difference between EMC measurement and EMI measurement
This page compares EMC measurement vs EMI measurement and mentions difference between EMC measurement and EMI measurement.
Compliance measurements need receiver which meets CISPR Part-16 for commercial test application and MIL-STD-461 for military test application. As per CISPR 16-1-1 receiver need to operate in frequency range from 9KHz to 18GHz. The receiver should have absolute accuracy of about +/-2dB. There are other EMI receiver requirements which should be meet for compliance testing as per CISPR specifications. Keysight technologies develops EMI/EMC equipments for such need.
The figure-1 shows four types of EMC measurements as described below. As shown EMI measurement falls under EMC measurement.
• Type-1. Radiated Emission : Ability of device to produce EM waves within limit such that it will not affect nearby wireless devices/systems.
• Type-2. Radiated Immunity : Ability of device/product to withstand against any nearby EM waves.
• Type-3. Conducted Emission: Ability of device/product to generate conducted disturbances/noise (if any) within limit such that it will not affect power lines/data lines. Practically there should not be any noise and if it is present then it should be blocked or reduced using some electronic circuits.
• Type-4. Conducted Immunity: Ability of device/product to withstand against any electrical disturbances or noises generated on power lines or data lines.
Following steps are followed during EMC measurement of conducted emission type with setup as shown in the figure-2.
➨Connect the Device Under Test(DUT) with test system along with LISN (Line Impedance Stabilization Network) and Limiter as shown in the setup.
➨Set frequency as per test.
➨Verify and note down ambient emission when DUT is in OFF state.
➨Now switch ON the DUT and verify signals using peak detector and note down the readings.
➨Now verify the EMC measurements made as per PASS/FAIL criteria with respect to standard requirements.
Following are the general guidelines for preparing EMI measurement of DUT(Device Under Test).
➨First determine location where product is going to be used. Based on this identify regulatory agency in that country.
➨Decide limits for as per conducted/radiated tests.
➨Select frequency bands to be tested.
➨Do proper calibration of any losses and gains of the modules used in the setup.
➨Identify signals to be evaluated and their pass/fail criteria i.e. limits.
Both the radiated Immunity and conducted Immunity tests fall under EMI measurements.
The figure-3 depicts radiated emission test setup. Following steps are followed during this EMI measurement.
➨Connect the Biconical Antenna with the EMI receiver and separate antenna from DUT as per regulatory specifications.
➨Set frequency and Bandwidth as per test requirement.
➨Do calibration with proper correction factors for the cable and antenna.
➨Verify and measure ambient emissions when DUT is in OFF state.
➨Switch ON the DUT and measure the readings now.
➨Now verify the result as per PASS/FAIL criteria according to the test specifications.
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