The programmable multi-p lexer channel selector is an important part of computer-aided system for on-line insulation monitoring of HV apparatus.The principle

the design method and the t est results for this selector are proposed in this paper.This device communicate s with computer by parallel port

enabling any4input channels with the signal con trolled by the computer from256input signals.It can meet the requirement for on-line insulation monitoring in large or medium-size substation.Meanwhile

the devi ce can also be applied in other circulating detection system which has many inpu t signals.