Ethernet communications is rapidly gaining popularity in industrial controller applications by enabling the instantaneous exchange of information between processing equipment and companies' Ethernet-based management systems.
According to thelol Open DeviceNet Vendors Association (ODVA™), the agency that sponsors both the DeviceNet™ and EtherNet/IP™ protocols, EtherNet/IP™ is a member of a family of networks that implements the Common Industrial Protocol (CIP™) at its upper layers. CIP™ encompasses a group of messages and services for manufacturing automation applications including control, safety, synchronization, motion, configuration and information. EtherNet/IP™ provides users with the network tools to use standard Ethernet technology for manufacturing applications while enabling Internet and enterprise connectivity.
Watlow product manager, Sean Wilkinson, says Ethernet technology is becoming widely accepted due to multiple factors, including: - the speed advantages over lower baud rate protocols
- the number of tools available for troubleshooting and optimizing a network,
- the broad base of competitive vendor support and solution options and
- the large pool of trained personnel who are familiarwith the technology.
In addition, the ability to bridge existing proprietary communications schemes makes it possible to phase in the use of Ethernet rather than having to replace everything at once.
Using EtherNet/IP™ specifically yields the advantages of an Ethernet network, as well as the advantages of the CIP™ designed for device-to-device communications. Those advantages include: - Explicit messaging, which allows devices to be configured via the network. A device can be detected and completely configured automatically in the event a piece of hardware is replaced.
- Implicit messaging, which allows efficient communication of data and instructions from one device to another or from one device to many consumers of data on the network. This minimizes network traffic and allows the speed advantage of Ethernet to be achieved.
- Assurance of interoperability. All devices are tested by ODVA and users can expect fewer problems when putting devices from multiple vendors together on a network.
- Integration with other EtherNet/IP™ compliant devices such as programmable logic controllers (PLCs) or touch screen human-machine interfaces (HMI).
"Traditionally, performing temperature control in a PLC can be difficult or can interfere with other program functions, so temperature is often controlled separately from the PLC. But in the past due to differences in the supported protocols, getting stand-alone temperature controllers and PLCs to communicate has been time consuming, costly and difficult," Wilkinson says. He adds that customers prefer temperature controllers outside of the PLC when performance of control loops is important or when the PLC application could be negatively impacted by incorporating the temperature controller, i.e. where there is significant motion control.
EtherNet/IP™ technology bridges that gap by allowing for effective and efficient temperature control to be incorporated into the overall control scheme.
"I always ask customers about what protocols they plan to use, and the question is often met with confusion since some users don't realize there are thousands of protocols that are designed to be compatible with, and coexist on, Ethernet networks," Wilkinson says. "It is natural to look to familiar functionality encountered on office networks and the Internet." Ethernet can be used to extend access to more remote users with support for web browsers and e-mail. It can also be used to connect devices together to integrate automatic functions by allowing, for example, a temperature controller to get its set point from a PLC or an HMI to allow access to parameters from a variety of devices.
The new EZ-ZONE™ PM controller from Watlow - the most recent extension of the EZ-ZONE product line - is the answer for those seeking a discrete PID controller, an over/under limit controller or an integrated thermal loop solution. The controller supports network connectivity to a PC, PLC or HMI using its serial communication options, including EtherNet/IP™, Modbus® TCP and Modbus® RTU to remotely configure, manage and monitor the system's performance. The EZ-ZONE is ideal for applications where space is limited and a 1/16 DIN panel mount is necessary.
Watlow's SERIES PD controllers utilize embedded Ethernet technology to provide a convenient, economical means for setting up and viewing key process variables. The SERIES PD controller is ideally suited for a broad range of temperature and process control applications where the operator interface is supported from a remote location. In 2005, the SERIES PD became the first temperature controller to offer ODVA Ethernet/IP™ conformance tested communications. This single or dual loop DIN-rail mount controller offers up to four control/alarm outputs plus up to two digital/current transformer inputs. The SERIES PD also provides a webserver for configuration and operation via a web browser such as Microsoft®'s Internet Explorer, as well as an e-mail client for notifying operators or service personnel of alarms and other conditions.
Watlow's EM gateway offers Ethernet connectivity for existing devices that communicate via the Modbus® RTU protocol on an RS-485 network. The EM gateway provides a quick, convenient and economical means of adapting controllers to Ethernet connectivity by bridging communications from Modbus® RTU on RS-485 to Modbus® TCP on Ethernet. The EM gateway also acts as a web server for supported temperature controllers, allowing users to remotely monitor the process variables and alarms. The user can remotely set the set points for temperature control in an Internet browser. Users can receive e-mail messages when alarms occur in supported controllers. The features of Ethernet protocols act as extensions of the user interface, making it more convenient for operators and supervisors to monitor processes and equipment. EtherNet/IP™ and DeviceNet™ are trademarks of the Open DeviceNet Vendors Association. Modbus® is a registered trademark of Schneider Automation Incorporated.
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