Built-in pump suction measurement, fast response, sampling distance of more than 10 meters. The multi-level calibration of the target point ensures the linearity and accuracy of the measurement. Waterproof, dustproof, explosion-proof, shockproof, intrinsically safe circuit design, antistatic, anti-electromagnetic interference. Concentration calibration misoperations are automatically identified and prevented, which can avoid defects caused by human factors. Three display modes can be switched: simultaneous display of four gas concentrations, circular display of single-channel gas concentrations in large fonts, and real-time curves.