Around the Loop

Feb. 27, 2009
Analog or Digital Process Controllers? It’s Clearly a Digital World.

The market for analog loop controllers has been declining for years. Replaced by the digital loop controller, the more modern microprocessor-based, single-loop and multi-loop controllers offer far more features and functionality than the older on/off controllers. Whether used in the home or in sophisticated factory controls, the new digital loop controllers offer communications, alarms, displays, setup/installation/commissioning, PID control, safety, wireless, Ethernet and small size.

According to a market research study by Venture Development Corporation ( titled “Industrial Electronic Temperature Controllers: Global Market Demand Analysis, Ninth Edition,” some users have difficulties in configuring, programming and setting up temperature controllers, specifically. “Increased functionality is not valuable to users unless the controllers remain easy to understand, configure/setup and use.”

Suggestions from users included menu-driven-based programming and flowchart manuals; intuitive configuration; and print manual with actual examples of hardware and software solutions.”

Most suppliers have followed their customers’ lead and are now producing loop controllers that incorporate many of these features, such as the products shown in this roundup.

Patti Pool
products Editor
[email protected]
Red Lion Controls
Data Station Plus and Modular controller product series now comes with a XCDN DeviceNet option card that can be added to the expansion slot during installation and configured using free Crimson software. The XCDN option card enables any connected devices to communicate with DeviceNet products to realize complete system integration and data transfer.  MODEL-PREDICTIVE LOOP CONTROL
Profit Loop is a generalized, model-predictive loop control and optimization software package that provides single input/single output model-predictive control and eliminates most PID-related control tuning, software and service. It can be used to control discrete analyzers, tank levels and long delay processes.
SOLO process/temperature controllers are available in four standard DIN sizes and come with a dual four-digit, seven-segment display. Starting at $89, the controllers offer dual-output control for managing heating and cooling processes and the built-in autotune function with PID control allows for fast setup. Control modes include PID, Ramp/Soak, ON/OFF and manual operation.
UTAdvanced temperature controller offers embedded ladder sequence control. It supports 52 ladder commands and 24 DIO points. The PLC capability allows engineers using temperature controllers and a small PLC to obtain the same control capability at the same cost of the temperature controller alone.
EZ-ZONE RM configurable multi-loop temperature/process controller incorporates an entire assembly of control loop functionality in a space-saving, DIN-rail-mount package. It can be configured with between one to 16 modules controlling from one to 64 loops. The controller can be used as a PID temperature/process controller, an over/under limit controller or these functions can be combined into an integrated controller.
Rockwell Automation
Allen-Bradley Bulletin 900-TC16 and 900-TC8 single-loop temperature/process controllers combine thermocouple and RTD sensing capability with either ON/OFF or analog outputs into a global temperature controller. They are also available with analog input and ON/OFF or analog output capability. Controllers are configured via four sealed keys and an 11-segment LED display and can be connected directly to a PC.
Advantech, Industrial Automation Group
ADAM-4022T dual-loop, PID serial-based controller offers an accuracy of ±0.15% for controlling temperature and other process variables. The utility software helps you select input and range configurations and set the operating parameters (SP, Sv, Pv, etc.) for process control needs. Installed on a standard DIN rail, the controller is powered by unregulated 10 Vdc to 30 Vdc and withstands ambient temperatures up to 60 ºC.
Moore Industries-International
Model 555 ¼ DIN controller handles flow proportional control, residual control, compound loop control with tag times and dechlorination with sulfur dioxide. Designed for water and wastewater applications, especially for chlorination and dechlorination, the controller’s front panel is NEMA 4X-rated and displays flow rate and residual chlorine simultaneously.
Control Microsystems
SCADAPack 350/357 SCADA controllers combine 32-bit processing with high-speed LAN and USB communications. The controllers have an integrated power supply, a 12 Vdc to 24 Vdc converter, an analog and digital I/O, serial communication capabilities and turbine flowmeter counter inputs. They use Modbus and DNP3 serial protocols, as well as Modbus TCP and UDP-based Ethernet protocols, and can be programmed locally through a choice of flexible programming languages.