Flow rates through the nozzlesv are controlled with the Spray- Mate II, manufactured by Micro-Trak Systems, Inc. The Spray- Mate II is reasonably priced, has a flowmeter range of 0.5 to 5 gallons per minute, and a console that is easy to use. The controller kit includes a console, flowmeter, Astro II GPS speed sensor manufactured by Garmin, electronic pump driver, and complete wiring harness.

Although most constant-rate systems use a servo valve to restrict flow, the Spray-Mate II uses an electronic pump driver to control the speed of the diaphragm pump, varying the pump pressure and the flow. Signals from the GPS and flowmeter feed information to the console, which controls the pump speed through the electronic pump driver (figure 4).

Figure 4—A flowmeter and GPS speed sensor feed information to the
Spray-Mate II control console. A signal from the console controls the
pump's speed through the electronic pump driver, maintaining a constant
application rate even when the ATV speeds up or slows down.