In the PLC/DCS control system on the industrial site, the measurement signal is often unstable. One is caused by electromagnetic interference, and the other is the infiltration of high-frequency signals. For example, the current signal output controls the inverter, and the high-frequency interference of the inverter infiltrates the signal. Among them, such interference signals make the frequency converter and valves work unstable. Installing a signal isolator between the signal connections of the two devices is one of the methods to solve the influence of electromagnetic interference and high-frequency signal penetration.