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12
6. CALIBRATION
To apply the correct volume of spray liquid to an area it is necessary to calibrate the
sprayer accurately. This is critically important to prevent under or over dosing of
pesticide. The calibration procedure is as follows:
6.1.
Measure the Forward Speed of the Vehicle
1.
Select a gear that will give an appropriate speed in the terrain of the spray area
and carry out a trial run over a measured distance of 100 metres. Measure
how long it takes, in seconds, to cover this distance (time = t seconds).
2.
Calculate the forward speed using the formula: Speed (km/hr) = 360/t
Example: time to cover 100 metres, t = 36 seconds, so speed = 360/36 = 10 km/hr
Note that the vehicle's speedometer is unlikely to be accurate at the low speeds
typically used for spraying.
6.2.
Select a Suitable Track Spacing
The track spacing is the distance between successive spray passes of the vehicle.
Spray passes should always be made with the wind at right angles to the direction of
travel of the vehicle. Although the peak spray deposit is likely to occur at a point
downwind of the vehicle some spray will be carried more than twice this distance.
Spray coverage of the target area is evened out by accumulating spray deposits
from overlapping swaths. This is known as an incremental spraying technique.
When using droplets of 50 – 75 µm (VMD) in diameter in a steady wind (in excess of
7 km/hr or 2 m/s) a track spacing of 50 – 100 metres will be possible in open areas
with sparse vegetation. A narrower track spacing will be necessary if larger droplet
sizes are used or if the sprayer is used in lighter winds. If necessary, the track
spacing can be determined by measuring the width of the swath deposited under the
prevailing operating conditions. As a guide, the track spacing should be less than
about 50% of the measured swath to ensure sufficient overlap of successive swaths.
MICRON AU8115MS VEHICLE MOUNTED SPRAYER
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