Facilities at Ratliff, Demmer & Anderson Walnut Hulling in Artois, Calif., use networked Opto 22 controls to manage a 100-ton nut dryer. Two double-wide 66-in.-diameter centrifugal fans and two 60-hp motors provide dry air while two direct-fired 10 million-Btu gas burners heat the air to 110°F. Applied Instrumentation engineers installed controls that include an automated moisture meter for measuring the moisture content of nuts in each bin. It reports back to a PC, which switches off the appropriate fan and burner when the nuts dry.

Facilities at Ratliff, Demmer & Anderson Walnut Hulling in Artois, Calif., use networked Opto 22 controls to manage a 100-ton nut dryer. Two double-wide 66-in.-diameter centrifugal fans and two 60-hp motors provide dry air while two direct-fired 10 million-Btu gas burners heat the air to 110°F. Applied Instrumentation engineers installed controls that include an automated moisture meter for measuring the moisture content of nuts in each bin. It reports back to a PC, which switches off the appropriate fan and burner when the nuts dry.


Drying and storage bins span three buildings at Tri-Counties Walnut Hulling in Ord Bend, Calif. To minimize conduit and wiring at the expansive facilities, Applied Instrumentation engineers networked Opto 22 controls and instruments throughout the plant. Typical enclosures there hold only three to eight solid-state relays with perhaps 16 to 48 high-level digital I/O points.

Drying and storage bins span three buildings at Tri-Counties Walnut Hulling in Ord Bend, Calif. To minimize conduit and wiring at the expansive facilities, Applied Instrumentation engineers networked Opto 22 controls and instruments throughout the plant. Typical enclosures there hold only three to eight solid-state relays with perhaps 16 to 48 high-level digital I/O points.


Integrator Applied Instrumentation (AI) found a way to move its agricultural controls to Ethernet without obsoleting systems installed years before.

The Concord, Calif., firm builds custom measurement and control equipment for agricultural and food processing. A typical task is to configure equipment such as grain dryers that remove moisture from stored commodities so they don't rot or mold. The controls for these devices are characterized by a handful of distributed I/O points of modest density handling such items as blower motors, moisture-sensors, heat exchangers, and so forth. Optomux I/O systems from Opto 22, Temecula, Calif., have managed these devices over RS-422 networks.

AI uses off-the-shelf CPU boards to manage the control logic for these systems. Problems arose, however, as the vendors of these boards stopped supporting RS-422 protocols and moved to more-sophisticated schemes such as JBus, Modbus, and others. And laptop PCs, which often served as monitoring platforms for many of the systems, stopped carrying serial ports. Meanwhile, customer facilities were growing ever more complex.

The integrator changed over to networks based around Ethernet. It updated existing installations with a new version of Optomux called the E1 model which supported Ethernet links. In facilities instrumented with serial networks, the E1 acts as a serial server which interacts with legacy Optomux hardware. So it takes a minimal amount of additional equipment and software to upgrade older installations.

The new systems also give AI personnel better access for field service. Old systems could only be debugged via laptops equipped with several serial port adapters able to work with various kinds of protocols. Now

technicians tap into networks at customer facilities simply by plugging an ordinary laptop into an Ethernet switch. Equipment can stay online while technicians perform maintenance and upgrades.

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