How did the PLC originate?

Mike Bacidore speaks exclusively with Dick Morley, the father of the PLC, to discuss its origin.

Mike Bacidore
CG1505 PLC

Control Design's Editor in Chief Mike Bacidore sat down with Dick Morley to discuss the origin of the programmable logic controller (PLC). In 1968, Morley participated in the creation of the first Modicon PLC for General Motors and therefore he is considered by many as the father of the PLC. This is just the first installment of a video series on the history of the PLC and Morley's involvement. Stay tune for more.   The reason works is because it is so simple.  

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Timeless Resources

Beginner's guide to differential pressure level transmitters

By David W. Spitzer

The importance of level measurement cannot be overstated. Incorrect or inappropriate measurements can cause  levels in vessels to be excessively higher or lower than their measured values. Low levels can cause pumping problems and damage the pump, while high levels can cause vessels to overflow and potentially create safety and environmental problems. Vessels operating at incorrect intermediate levels can result in poor operating conditions and affect the accounting of material. Learn more.

Controllers: Direct vs. reverse-acting control

By Bela Liptak

Valve failure position is determined by safety considerations. If, in case of failure, you want your column to go on full reflux, your selection where the reflux control valve is fail-open, and net overhead control valve is fail-close, is right. Assuming that the valve actuators are spring-operated pneumatic ones, and assuming that you define "failure" as the loss of air supply, the spring will act to open a fail-open (FO) valve and to close a fail-closed (FC) valve, regardless what the controller actions are. Read more.

Voices: Ask The Experts

What's wrong with my thermocouple? How do I know my RTD measurement is accurate?

Our experts tackle these not-so-simple problems

By Bela Liptak

Q: Thermocouple Diagnosis Our Type K thermocouple at 25 ºC generates 1.0 mV. It has a long TC cable which does not show continuity, but 130 ohms resistance. Can you explain why this is occurring and how it can be fixed? Ashish Garg A: One of the problems associated with…

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Control Talk Blog

Best Control Valve Flow Characteristic Tips

Often arguments as to whether a linear or equal percentage trim is best are based on the theoretical inherent flow characteristics. Valve rangeability is often stated as simply a deviation of the catalog flow characteristic from the theoretical characteristic. Here we will see how the consideration of the changes in process dynamics, available valve pressure drop, and control valve dynamics can alter what you consider as the best flow characteristic. 

Control Talk Blog

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