A Chemical Metering Pump is seldom used by itself. It is usually a part (ok, the part) of a chemical injection system into a process. Such a system requires various accessories, valves and controls to dispense the exact amount of chemical demanded by the application which may itself vary. Let us say if you are using chemical pump to achieve pH balance for the water. You need to measure the pH of the treated water and based on it decide if you need more acid to be injected. Such controls require you not only to monitor, measure and control but also to adjust dynamically as the conditions change. You need to have the flow meters, PLCs and valves all communicate with each other and deliver the desired result which in this case may be a pH value of 7 for the treated water. This is just one of the many applications including fertilizer dispensing, disinfectant chemicals for water, anti-scalant for pipes or boilers, anti-corrosion chemicals for oil extraction etc. etc.