Knapsack Calibration

Welcome to the Knapsack Calibration course.

This course has been designed to help you understand the basic calculations that are required to accurately calibrate a knapsack sprayer. The easiest way to do a quick calibration is as follows:

• Prime the sprayer by adding a small quantity of clean water and then pump out through the lance until air can be heard ‘spitting’ from the nozzle.

• Now add exactly 1L of clean water to the tank and spray it out in a straight line holding the lance at a comfortable set height on a path or drive, walking at a natural speed.

• Measure the spray width and the length of path sprayed and then calculate the area covered by the 1L of water

(spray width x length = area for 1L)

• Multiply the area for 1L by the capacity of the sprayer to work out how far a full tank will go [A]

(e.g. if you fill to 20L then; 20 x area for 1L will give you the number of m² per tank.

To work out the amount (g) of product to add per tank fill, do the following simple calculation:

• Take the dose from the product label and divide it by 10 – this figure is the number of grams (g) of the product for each square metre [B]. e.g. ‘Ferromel 20’ should be applied at (a maximum of) 25 kg per hectare so this would be 2.5g per square metre.

• Now multiply the area covered by each tank [A] by the amount of product needed for each square metre [B] to find the amount of product required for each tank full. [AxB grams]

• Mix the ‘Ferromel 20’ in a bucket using warm water if available

• When fully dissolved add the solution to the sprayer tank then top up with the remainder of the water.

• Mix thoroughly before spraying.