Automatic zero tracking to prevent drift. With standard bus system RS485 output (RTU format). Three-wire 4-20mA standard signal output, voltage output, 2 groups of relay switches. It can be connected to the computer to monitor the concentration of the field probe in real time through the host computer, and store, analyze and print the data on the computer. Anti-explosion, lightning protection, anti-static, anti-reverse connection, anti-EMI, EMC electromagnetic interference, anti-impulse surge current impact.