DWS-51A is an intelligent laboratory Sodium meter. It is equipped with the dedicated laboratory ppb sodium ion measurement electrode and the reference electrode, with the static measurement performance in the beaker greatly improved, compares with the traditional sodium meters. As long as the user pays attention to the electrode cleaning, the satisfactory result can be achieved. It can be widely used for continuous monitoring of sodium ions of the solutions in thermal power plants, chemical fertilizer, metallurgy, environment protection, pharmaceutical industry, biochemical industry, foodstuff and running water.