The Investigation Of The Uncertainty Sources Of The Power Port Conducted Emission Measurement

In the power port conducted emission measurement,the uncertainty sources of influence measurement result usually include the two important categories:the measurement instrumentation uncertainty (MIU) and the intrinsic uncertainty of the measurand. for the measurement instrumentation uncertainty (MIU) ,this paper mianly investigates the variation of the phase angle of the artificial mains networks(AMN) impedance on introducing the uncertainty of measurement result of the power port conducted emission.the measurement results demonstrate that the variation of the phase angle of the artificial mains networks impedance will introduce very large uncertainty for the power port conducted emission measurement results.while the impedance module of the equipment under the test(EUT) equals to the impedance module of the artificial mains networks,it will occur the maximal error value.the maximal error value is greater than 13dB.while the impedance module of the equipment under the test is far less than or more than the impedance module of the artificial mains networks,the measurement error only depends on the phase angle of the artificial mains networks impedance,but is not related to the phase angle of the equipment under the test.this paper also measures the phase angles of the several artificial mains networks impedance that the laboratory always used.the measurement results manifest that there are the distinct differences among the different manufacture's artificial mains networks impedance phase angles , especially the higher frequencies of conducted emission measurement. for the intrinsic uncertainty of the measurand,this paper mainly investigates the variation of the measurement setup on introducing the uncertainty of measurement result.it takes the eight possible variations of the measurement setup into account.for example,the height variation of positioning the equipment under the test , the distance variation between the equipment under the test and the vertical ground reference plane,etc. then the measurement is performed by using the typical equipment under the test(the faxmachine with the switching power supply). the measurement results demonstrate that the small variation of the measurement setup will introduce the very distinct uncertainty for the power port conducted emission measurement results,especially the higher frequencies of conducted emission measurement. There are the differences of more than 20dB among the measurement results.