A motorized knapsack sprayer is made just like the manual knapsack sprayer but with an engine to increase efficiency of the sprayer. With a motorized knapsack sprayer one is able to spray large pieces of land quickly. Also, since they have more pressure and can throw the liquids far than manual sprayers can, the motorized knapsack sprayers are ideal for spraying fruits even 10 meters up a tree.
There has been little improvement to the design of the knapsack sprayer since it was invented in the 1800s. Changes made have been to enhance efficiency but the operating principle of the knapsack sprayer remains the same. A knapsack sprayer has a pump that is used to create pressure to push the liquid out through the nozzle.
The manual system can either have a diaphragm or piston pump. Piston pumps are however more preferred because of the high pressures they can attain. As the lever is pushed up, pressure falls inside the pump and the liquid is drawn in through a valve from the tank. As the lever is pushed down, pressure inside the pump chamber rises pushing the liquid up the chamber, through hose and out of the nozzle at fast speeds.
In a motorized knapsack sprayer, the engine moves the piston up and down instead of using the manual lever. With a motorized knapsack sprayer, consistency is achieved as the engine creates the same kind of pressure throughout. This ensures uniformity in the level of chemicals applied to the plants. The engine provides more power than a human hand is able to which increases the pressure in motorized knapsack sprayers significantly.
With the high pressures and the boom nozzles and even double nozzles, applying chemicals on farms is now quite easy and fast.