Dealing with large EMC uncertainties

In the subject of EMC the maximum field strength emitted from an equipment under test (EUT) may only be known to an uncertainty of ±10 dB. This is in stark contrast to other fields of metrology in which a physical quantity is measurable to better than one part in 10 ⁹. In the latter case the method of summing uncertainty components is well established. In the relatively young subject of EMC there has been little incentive to relate uncertainties to the measured result when comparing it to the pass/fail limit level for a radiated emission test. The current EMC standards do no require this and there is a temptation to use high uncertainties as an excuse for lack of rigour in the measurement method. The main purpose of this paper is to show that it is worthwhile trying to reduce the uncertainties of the components of an EMC uncertainty budget. If the uncertainties of all but the largest component can be reduced, it becomes possible to devise meaningful tests to reduce the latter