Pre-Compliance Conducted Emissions Test - The ABCs of EMC (E03)

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Learn what EMC is, and how to go through a Conducted Emissions test for pre-compliance testing.
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Transcript:
Emissions are everywhere.  Emissions consist of unwanted signals from any electronic device.  For example, an unclear radio signal near several devices.  Hi everyone – my name is Matt Campbell and I’m an engineer here at Keysight and welcome to “The ABCs of EMC series.”  In the last episode we went over what radiated and conducted emissions testing is and the different types of standards your device needs to meet.  
Today, we will go through a conducted emissions test.  
Conducted emissions tests focus on the unwanted noise propagating by a conducted path, like a power line or long cables.
This type of testing is one of the first group of tests performed in the process for compliance, but the second part of emissions testing in pre-compliance measurements.

For this type of measurement, you will need a signal analyzer with precompliance measurement software, a LISN, a limiter, and of course, the DUT.  The LISN, also known as the line impedance stabilization network.  The LISN is important because it isolates power from the DUT.  The limiter is to prevent excessive input power that would damage the front-end of the signal analyzer.  To make sure what you measured is purely from your DUT, you need to filter out the noise coming from the power line side.  This is done with the LISN, which essentially heavily filters from the power line side.  To ensure unwanted signals aren’t generated, keep the cord between the DUT and the LISN as short as possible.

Now it’s time to make the first measurement.  Measure the signals on the powerline with the DUT on.  If you see a signal approaching these limit lines, these are unwanted emissions from the DUT which means additional shielding is required.
Next we will select the frequency range in the measurement application.  Select any frequency ranges that are not being used.  For pre-compliance tests, the range is set from 9kHz to 150 kHz for A band, and from 150 kHz to 30 Mhz for B band.    Once the frequency range has been selected, load the limit lines and the correction factors found in the pre-compliance measurement application.  These create the bounds of which the signal needs to be within, to make sure unwanted signal levels are below the required limit.  To compensate for measurement uncertainty, add a margin to each limit line.

Conducted emission
To measure the quasi peaks and average of the signals, they need to be measured and compared to their respective limits.  The EMC application sets this up in the quasi-peak detection mode.  Step through the detector that you need, and view the measurement results.
Conducted emissions are characterized by both quasi peak detector and average detector.  Those two different types of detectors are used to quantify different types of signals, like pulsed and continuous.  To pass the test, the results from both detectors should be below their limits.
The quasi-peak detector delta to Limit line 1, and average detector delta to limit line 2 should all have negative values.  
If there are some measurements that are positive, then there are conducted emissions present from your DUT.  Now you know if your DUT needs further re-design or troubleshooting, which has saved your time and money, with this pre-compliance test.

For more information on conducted emissions testing, check out the app note, with the link below.  Thank you for watching!

#EMI #EMC #RFEngineering #ConductedEmissions #PreCompliance #EMIPrecompliance #EMCPrecompliance #SpectrumAnalyzer #PrecomplianceTesting #PrecomplianceTest

YouTube url:	https://youtu.be/fsasa02IvYo
Created:	11. 11. 2020 16:46:40

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Pre-Compliance Conducted Emissions Test - The ABCs of EMC (E03)