Programmable Logic Controllers Product Focus Study, November 2004
Research was undertaken to gain a better understanding of Control Engineering subscribers’applications and needs regarding programmable logic controllers (PLC’s).
•Among those who specify, recommend, or buy PLC’s, 81% do so for in-plant requirements, while 41% do this for OEM needs.
•Micro and medium are the most widely installed types of PLC’s. The most wide-spread applications of PLC’s are for process and machine control.
•Three in ten report their PLC’s network with personal computers. Nearly as many indicate their PLC’s stand alone.
•Serial RS-232/RS-485 and Ethernet are currently the most widely used communication protocols. However, declining usage of Serial RS-232/RS-485 over the next year will catapult Ethernet into the top spot. Among those who use Ethernet, 79% use it as a supervisory network. Nearly two-thirds use it to network PLC’s. Among those who use Ethernet, 83% use TCP/IP as their protocol. EtherNet/IP is the second most popular protocol among this segment.
•Virtually all respondents use ladder diagrams to program PLC’s. This is more than double the usage of any other programming language.
•Built-in communication support is clearly the most important factor to survey participants when buying a programmable logic controller CPU.
•PLC’s with more remote I/O subsystems and universal programming software for multiple hardware targets/platforms are the most common features survey participants expect to specify in future PLC purchases.
•Analog, discrete, and communication are the most widely used I/O modules.
•The term PAC currently represents different things to different people. Most think of it as being like a PLC, but more 'open'. However, nearly as many consider a PAC to be a PC-based processor in a rugged PLC-like package. Comparable numbers think of PACs as supersets and subsets of PLC’s.
•Rockwell Automation, by a wide margin, tops the list of PLC manufacturers purchased from in the past 12 months. Virtually all of those control engineers surveyed are satisfied with their suppliers, with nearly two-thirds being very satisfied. Fifty-seven PLC’s was the average number each survey participant purchased (from any manufacturer) during the past 12 months. This equated to average spending of $182,751 per respondent. Our data suggests PLC purchases will only grow in the year ahead.
•Sixty percent of Control Engineering subscribers responding do not receive IAN. Of the publications listed below, Control Engineering is the only one received by 22% of respondents.