May
19
In a blog posted late last month I addressed how to provide a 24VDC source of power to a three wire field device. In the past I have used a 24VDC High Side Discrete output to provide 24VDC to these types of devices. This solution can be implemented in most DCS and PLC systems. If …
May
05
A book goes through many reviews and edits before it can be published. Still, it is very difficult for the authors and reviewers to catch all the typo’s in the original text and those that are introduced during the type setting process (formatting for publication). ISA recently notified me that the book that Mark Nixon …
Apr
28
Some field devices such as an inductive proximity switch may be designed as three wire devices that require a 24VDC source of power. In such cases it is possible to tap into the 24 volt bulk power supply in the rack room and run twisted pair to the device. However, to protect against a short …
Apr
21
During the TC65 Plenary meeting each working group gives an activity report that summarizes the status of standards that are being developed or updated. At the Hamburg meeting, March 31- April 4th I was a delegate to the SC65B and SC65C meeting and lead the US delegation in the SC65E meeting. The reports by Peer …
Feb
11
It can be shocking to examine control utilization in a plant where performance tools have not been installed and/or not used. For example, in the mid-1980s a control survey was conducted at a major pulp and paper plant where the control system had recently been updated to the latest distributed control system. At that time …
Jun
25
To ease operator transition from panel-based systems to monitor-based systems, the manner in which first generation Distributed Control Systems (DCS) displayed information often mimicked the way this information had earlier appeared on the control panel. Since the control interface provided by the control panel was familiar and had proven to be effective, a similar presentation …
Mar
05
There are significant difference in the frequency and manner in which anew measurement value is updated by a wired transmitter vs. a wireless transmitter. Thus, it is natural to question what impact this has whena wireless transmitter is used in closed loop control. Since most wireless transmitters are battery powered, it is desirable to minimize …
Feb
08
Virtualization technology has advanced a lot over the past 10 years. Most IT organizations now make extensive use of virtualization technology to consolidate servers and manage very large numbers of users. Virtualization provides a much improved architecture for isolating applications from hardware changes, securing systems, providing patch management, and improving power management (in large data …
