Measurement uncertainties in screened rooms and in open area test sites-a tutorial introduction

The paper presents the main factors which contribute to uncertainties in measurements in screened rooms and in open-area test sites (OATS). EMC standards require test measurements to be made on equipment under specified conditions in order to demonstrate compliance with various national and international regulations. In order for these tests to be meaningful it is necessary that the EMC behaviour of equipment under test (EUT) in different environments should be predictable, consistent and repeatable. In particular, it is desirable that measurements done on the same EUT in different vendor´s premises are broadly similar and that measurements done in screened rooms and in OATS can be correlated. Unfortunately, these aims cannot be met at present and hence a deeper understanding and control of the various test environments is necessary to improve the accuracy and consistency of measurements. In order to help with this process, the main issues involved are addressed. Conditions encountered in screened rooms, OATS and other test environments are examined