The technology involved in controller and application equipment are summarized in the following sections. The heart of variable rate application lies in the controller, which is a microprocessor or PC-type computer that ties in with the machinery and controls and monitors application rates. Controllers may vary in complexity from one channel to 260 channels, each channel controls one chemical or seed type. A controller may be built specifically for a system, or may be an entirely seperate unit that can operate on many different types of machinery. A controller may interface with a PC compatible computer to record the day's data, this may occur through a direct connection, modem, or memory cards.
Most controllers contain a ten year non-volatile memory.
Controllers that do not work directly with a PC have some type of LCD display that shows application rates, travel speed, amount applied, area covered etc. Additional diagrams are in the text, they include a Precision Farming overview, a typical on-tractor sprayer set up, and an anhydrous ammonia system. The TASC 6200 by Midwest Technologies, Inc., controls up to two booms, for either sprayer or spreader applications. The TASC 6500 also by Midwest Technologies, Inc., controls up to five booms. The TeeJet 855 Controller is for Sprayer application, and is manufactured by Sprayer Systems.