Abstract: To ensure the safety and reliability of the safety level distributed control system (DCS) for live analog signal acquisition, it is necessary to place an isolation distribution device on the front end of the analog acquisition of the DCS. Capacitor charge-discharge was used for analog isolation, and timer and logic gate circuit were used to generate switching control timing signal. The function of isolating the analog signal by using the photoelectric switch, adjusting the charge-discharge time of the capacitor and controlling the timing of the sampling and holding. The isolated voltage signal was converted into a current signal output through the circuit. Through the selection and matching of the parameters of the timing control device, the device has good electrical characteristics and a wide range of application scenarios. Under the condition of uncalibration, the accuracy can reach 0.05%, the temperature drift is less than 2×10-5/℃, and the electrical isolation reaches 1500Vp@1min<5mA (Vp is the peak voltage).

Key words: analog isolation; low-temperature drift; high-precision; capacitor charge-discharge; timer; sampling and holding