The idea of linking several irrigation controllers over a large site to operate from a single location has long been an appealing one. What better way to monitor and manage a 100-plus acre site? And not just the irrigation system -- master valves, pumps, lights, fountains, gates, security and essentially any other function that runs on 110 power and can be programmed to start and stop.

Central control systems and their satellites and software can be as varied as the sites that they help to manage. Careful consideration of all of the packages and options should be undertaken since this involves a large investment in time, money and resources. Both hardware and software, and their performance together, should be matched to the site and the end user for versatility, simplicity, reliability and durability.

Considering Hardware

Communication options are plenty, both in their linkage among satellites and the central computer, and in their networking and transmission. The site should determine whether hardwire or radio, or some combination of the two, is the most reliable and least expensive conduit for transmission. Site characteristics, like total acreage, distance from the central to the furthest satellite, topography, structures, nearby facilities that might be using radio transmission, cultural activity and others, should be factored into the decision.

    • Hardwire Connection -- A wire path installed specifically for connection from the central to the satellites. Generally, hardwire is only feasible where computer and field units in close proximity.
    • Phone Line -- Used to communicate from the central to field cluster units using a data-quality phone line (usually less than $10/month). These lines are maintained by the local phone company and are generally as reliable as that service.
    • UHF radio -- Licensing required. Usually not used where distances between the central and satellites exceed half a mile. Reliability can be affected by obstructions and frequency interference. Survey the area for others who might be using frequencies that you are considering before purchasing any equipment that might have a preset frequency designated.
    • Trunk radio -- Can access locations where a wire path is geographically or financially prohibited. The reliability of transmission and reception is tied to the trunking tower facilities. Usually used in distances up to 30 miles from the trunking tower.


Dedication and Devotion

Today's marketplace offers less expensive computer hardware and more flexible methods of phasing in a central system to a site. Field satellites can be installed and programmed one at a time. The ability to program the system from a satellite in the field is an attractive benefit to many water managers. As each is brought on-site, it can be linked to a designated master controller and programmed. This enables municipalities, highway departments, airports amusement and industrial parks, and more to approach central control gradually, softening the educational and financial demands.

Dedicated computer packages are employed only by the irrigation system -- no inventory, personnel scheduling, payroll, and the like can be performed by the computer. Because the computer is used exclusively for controlling the system, is can continuously monitor, record and respond to feedback from the field. Weather stations, moisture and wind sensors, flow sensors and monitors provide powerful data on which to base irrigation schedules. Remember, too, that entire irrigation systems relying on a computer can shut down if there is a computer failure.

The variety of communication functions and properties in the marketplace are too numerous to discuss individually. However, understand the chain of command and the role each component plays in transmitting messages to satellites and receiving messages from them, and whether or not a satellite can operate as a stand-alone. Some centrals communicate directly with satellites and back, others process information through a intermediary processing unit before it is fed to the end receiving units. The more components involved, the more parts to "break".

Hardware apparatus, like weather stations and other sensory feedback devices, are invaluable to the effectiveness of central system. Scheduling irrigation according to real-time evapotranspiration (ET) data enables the astute water manager to match water applications precisely with site needs. Flow sensors can automatically shut down part or all of the system while continuing irrigation sets unaffected by a breach in the piping system. Flow monitors alert the operator to any discretion in water applications, from sticking valves to broken risers, while providing valuable tracking data on weekly, monthly or annual water use. Moisture sensors can be used in selected areas to ensure that soil depletion levels don't exceed a preset threshold -- for example, a south slope of turf, where constant sunlight and runoff might be a problem.

Shop `Til You Drop

An exhaustive research and comparative procedure will ensure that you select the best possible product to fit your site and budget. Ask for a demonstration of the central and satellites. Manufacturers are willing to give you their time, so use it.

A few things to consider when sampling the software include features and functions; versatility and user friendliness; graphics and display; and training and support. Remember site conditions, like water sources, pump stations, control zones and the like, and your crew -- who programs the computer and their knowledge of and experience with the equipment.

Scan the main menus to get a feel for how data hungry and user friendly some of the functions are. Just because a feature is listed on the menu, don't assume that it's included in the package. Question how specific software features interact with one another and if there are any limitations to their uses. Are there additional pieces of equipment (a weather station, for example) that must be purchased to use these menu items? Are there functions you need that don't appear on the menu?

Different software packages might have similar features, but their programming and operation can be very complex and intricate, or very uncomplicated and receptive. Generally, the more versatile the features, the more complex the operation, because several features rely on one another for specific data generation and performance, like flow and fertigation.

You can't beat a good education. Training and support are integral to the success of a system's design, installation and operation. Ask for references, and follow them up. it's important to know how quickly a manufacturer or distributor responds, over the phone or on-site. Support for the end user should go well beyond initial start-up and programming.

In addition to education and training support, ask about system maintenance and the role of the distributor. Do they stock every component of your system? Are there backup circuit boards or satellites available? Are they certified by the manufacturer to perform repairs, or do they send repairs out? Anyone who has had extensive downtime in July or August and watched the plant material stress to dangerous extremes knows the importance of this kind of support.

The dynamic technology evolving in irrigation central control can be both exciting and a little scary. The future of water management is at your fingertips, but make sure you grasp it one finger at a time. When you have a firm hold, your job will be easier and your performance improved.