The instrument adopts negative pressure suction sampling, built-in air pump, which can effectively remove water mist and other impurities in the sample gas, and has the function of automatic zero correction. Conventional measuring range is 0-500/1000ppm, measuring unit is ppm, resolution is 0.01ppm, measuring accuracy is 2%FS, signal output is 4-20mA and RS-485. Auxiliary functions: automatic zero correction, temperature compensation, pressure compensation, light source compensation.