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These days, manufacturers are putting more functionality into smaller-sized loop controllers, making it possible to shrink the the size of machines and control panels and reduce overall cost. However, many applications require more functionality than these tiny loop controllers can deliver. For instance, if end users have a variety of controllers from different vendors, networking is a highly attractive alternative. They can connect single-loop control to high-function networks such as DeviceNet or Ethernet. Then Internet connectivity is easy, which opens up a range of communication possibilities.
Dennis Schneider, product manager at Rockwell Automation says, “Loop controller trends currently include reduced costs and increased connectivity. The price of display technology has gone down, allowing integrated controllers to display more readable configuration and program characters. As the cost of microprocessors diminishes, control is getting faster, allowing improved intelligence and more communications with supervisory controllers.”
Paul Sagues, president of Berkeley Process Control, says, “The future direction of loop control is clearly toward more distributed nodes on standard networks. Whereas peer-to-peer architectures have been built as custom software applications, we see these identical, single-part-number, distributed modules using peer-to-peer architectures that are configured, not programmed. On some new semiconductor tools, we see the trend toward hundreds of such modules doing closed-loop temperature, pressure and plasma control control with nodes sharing information seamlessly.”
FOUR ZONE TEMPERATURE CONTROL
EMC 4Z controller offers the control capabilities of four single-loop controllers, plus auto tuning on a control board measuring 4.5 x 7 in. for embedded machine design applications. The board’s basic capabilities include four 16-bit analog inputs that can be standard process types (4-20 mA or 1-10 Vdc), or low-level sensors such as TC, RTD, thermistor or smart sensors that require excitation voltages of 5, 10 or 15 Vdc. The board’s 14 MIPS processor handles the four PID control zones in addition to the two encoder/counter inputs. EMZ 4Z has 256K flash code and 8K RAM memory.
DUAL SETPOINT CONTROL
Control-RRR units operate pumps, valves and alarms based on a dual set point control algorithm. Each unit includes up to four control channels, and can display data from up to four sensors. The control is telemetry-ready for spread-spectrum radio, so sensors can be connected both locally and/or at remote sites. Each control output is associated with a sensor that provides feedback information to the controller. The controller compares sensor readings with two set points to determine whether to turn the control output on or off.
UNIVERSAL DIGITAL CONTROLLER
Honeywell Process Solutions
UDC3500 ¼-DIN universal controller is available as a single loop or dual loop controller. The waterproof NEMA 4X/IP66 faceplate allows it to be used in washdown applications. Software makes controller configuration easy. A wireless infrared communication port enables controller setup from a Pocket-PC or computer. Ethernet communication allows connection to plant-floor networks. Application flexibility is assured with up to five analog inputs, math and logic functions and AccuTune III tuning with fuzzy logic overshoot suppression.
CN79000 1/32 DIN dual-zone controller offers five thermocouple input types, and each zone offers a single set point. Features include independent fuzzy logic, autotune and peak/valley indication for each zone, plus free software. RS485 Serial communication is optional. The CE compliant controller can be used for food processing, automotive-engine testing, water and chemical tanks, plastic molding, and temperature control applications.
Solo process/temperature controllers include 22 models, including 11 under $100. Available in four standard DIN sizes (1/4, 1/8, 1/16 and 1/32), each unit is equipped with a dual four-digit, seven-segment display, which is useful for process variable display. Each model offers dual-output control, making it suitable for heating and cooling processes. The built-in autotune function with PID control feature allows easy startups. Control modes include PID, ramp/soak, on/off and manual operation. Universal inputs are standard on all controllers, including thermocouple, RTD, mA, mV and DC voltage. Select models are equipped with three available alarm groups.
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