In order to meet the needs of the sensor output parameter measurement of a domestic aircraft operating system, do a realtime monitoring of an LVDT/RVDT principle of sensor output, because its impedance causes the backend equipment load effect to be bigger, at the same time to ensure that the test equipment does not cause a security problems for the original operating system, therefore, an isolated differential AC signal conversion equipment is designed in this paper. The device can be LVDT/RVDT sensor output of the two differential AC signal into its linear relationship with the actual physical quantity of DC output; at the same time, the output terminal adopts highimpedance passive transformer isolation mode to ensure that the original system does not cause interference, and to meet the smaller load effect. After simulation and test, it shows that the design is simple and reliable, with certain feasibility.