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Industrial Products in Spotlight

PLC & HMI Controllers

Five factors to consider when selecting one of these device

Posted on November 7, 2016 - ( views)

by Marta Roberti

Unitronics offers a wide range of PLC & HMI controllers and helps customers choosing the right devices. Selecting the manufacturer that stands behind a brand of controllers is a major decision. It is every bit as important as your CPU and I/O requirements. Here are 5 factors to consider when making that selection.

1. The PLC: Broad Range of PLCs

The selected brand must have a complete, full product range that can meet the requirements of your customers. PLCs, for example, must be able to supply sufficient memory to support I/O, log and manipulate historical data, as well as execute the control program. Where execution speed is critical, the CPU processing speed must be considered as well. Influenced by the mobile industry, customers expect HMI color touch-panels to provide the communication window between operator and system. In cases where space is at a premium, PLC + HMI all-in-one controllers have a distinct advantage. Some PLC manufacturers provide PLC + HMI controllers with onboard or snap-on I/O modules, which, in addition to saving space, also greatly reduce wiring.

2. Communications: Data Communication & More

Flexibility is key. Important industrial datacom protocols include MODBUS, CANopen and other flavors of CANbus such as CAN Layer2 and EtherNetIP. Some brands also support protocols such as SNMP and FTP. Web Server—the ability to access a PLC via web browser— and VNC support are excellent methods of remotely accessing a PLC, while SMS messaging and email are very handy for notification via mobile. You may also want to look for GPRS/GSM modem support.

3. Programming: Look for Intelligent Software

Saving time is the primary benefit of intelligently designed software. There are two particularly important factors to consider:

  • Ease of use – ergonomic design means that you do not need to search for elements when programming. In addition, logical, consistent construction saves time, since the programmer intuitively knows what to do even when programming a particular task for the first time.
  • Re-usability - Insist on it. Whether you are programming Ladder or C functions, designing HMI screens and Web pages, or creating custom controls, the ability to re-use your work across projects will save big chunks of time.

4. Maintenance: Service and Support

PLC manufacturers should offer a high level of customer care. Personal support –meaning from people, not automated systems, that is available 24/7 is extremely valuable. This is what can make the difference in meeting deadlines and retaining customers.Support documents, specs, and guides, should be readily available and free.

5. Cost: Total Cost of Ownership

Cost is not limited to the actual cash you pay to purchase the PLC. Development costs and future maintenance costs can make or break the profit margin. Therefore, when purchasing a PLC, remember to select the company behind the PLC.


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