The aim of this paper is to highlight the problems that arise when the immu
nity of measurement instruments to power line voltage disturbances has to b
e evaluated. The lack of an international product standard puts at the user
's disposal only some basic standards which, in giving only general criteri
a for test result classification, make it difficult to choose suitable acce
ptance criteria and, consequently, to plan a proper set of tests, especiall
y for very complex instruments.
After an introduction on the state of art of electromagnetic compatibility
(EMC) international standards, a measurement technique adopted by the autho
rs to evaluate the immunity of complex instruments to conducted disturbance
s is presented. Finally, experimental tests carried out on VXI instruments
are given and discussed exhaustively.