The mixed sample function can provide uninterrupted mixed water samples to the online monitor, which can effectively avoid and make up for the shortcomings of the online monitor's intermittent measurement of point instead of surface in the sampling blind area during the measurement period. Derun Houtian water quality automatic samplers are widely used in pollution sources, sewage treatment plant imports and exports, and are used online with COD, ammonia nitrogen, heavy metals and other online monitors.