Considering two cases

one the power frequency electric field varying

the other the high-frequency electric field varying caused by corona

this paper realizes the on-line diagnosis on the variation of internal gas pressure of vacuum interrupter in service. The optical fibre network is used to connect the measured points with the host computer. Each point is checked in series. The accuracy is improved through adopting high-speed sampling board and digital signal processing technology. The acquisition section of electric field signal is isolated from the section of signal transmission electrically

which can withstand the rated power-frequency voltage and other overvoltage.