Agricultural Crop Spraying
 PROBLEM:
Fertilizer, insecticides and herbicides all represent a major expense in
today's agri-business. Misapplication, putting on too little or too much,
can be additionally expensive in terms of reduced effectiveness, lower crop
yields, or wasted materials. It is to the farmer's advantage to be able to
apply materials to his acreage at known and uniform rates. Most crop treatment
material is applied by spraying a liquid or slurry from a tractor-pulled and
powered implement. The implement consists of a tank, pump (centrifugal or
positive displacement), and associated valves and instrumentation. It also
consists of a number of 'booms,' pipes which receive the liquid and spray
it from a series of nozzles spaced at equal intervals.
Tabular data has been prepared relating nozzle size, liquid pressure, and
tractor speed to the gallons/acre. This data is used to program a microprocessor
which automatically controls pressure at varying levels as tractor speed is
changed. A pressure transducer and rotary encoder are used to sense nozzle
pressure and tractor speed.
There are a number of factors, which make this pressure measurement difficult
for the transducer:
a great many of the materials being sprayed are intensely corrosive and
abrasive
there is a possibility that the system will have severe overpressures or "spikes"
there is the environment: rain, dust, RFI, shock and vibration.
SOLUTION:
A Mediamate? pressure transducer is mounted at the end of a short length
of hose filled with kerosene. The other end of the hose is connected to the
bottom of the tank. The transducer is in the cab of the tractor and connected
to a microprocessor. The kerosene-filled hose damps pressure spikes and keeps
corrosive (and clogging) slurries away from the transducer. Additionally,
the hose places the transducer out of the weather.
ENVIRONMENT:
The transducer sees blowing dust and water in spite of its in-the-cab location.
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