Dedicated Controls

Dedicated Controls June 1, 1998

Opto 22 ‘SNAPs to it’ with new controllers, I/O devices

To help users implement cost-effective, PC-driven controls, Opto 22 recently launched its new family of Snap controllers. The Snap-LCSX and Snap-LCSX-Plus controller can reduce the entry barrier to flowchart-based, fully integrated hardware and software control solutions, according to Opto 22's developers.

By Staff
Dedicated Controls May 1, 1998

Single-Loop Controllers Dominate Marketplace

In 1942, John G. Ziegler and Nathaniel B. Nichols devised the Ziegler-Nichols Closed-Loop Method and Equation (aka PID). At that time, loop control was, at best, "cut-and-try." The hardware that Mr. Ziegler developed to make the Z-N method successful included the first pneumatic controller with reset (integral) added to the gain (proportional) control, as well as the first controller with...

By Staff
Dedicated Controls April 1, 1998

Manage the Whole Process with Multivariable Control

Single-variable controllers such as PID loops are by far the most popular controllers for industrial applications. A single-variable controller measures the one and only variable of interest, decides if its value is acceptable, applies a corrective effort if necessary, then repeats. This routine works very well for process control problems with just one variable or with multiple variables...

By Vance J. VanDoren, Control Engineering
Dedicated Controls March 1, 1998

Prewired PLC Cables

Irving, Tex.— The new Interfast product line from Entrelec is a family of prewired cables and connectors that simplfies interconnecting field wiring to PLCs. Individual wires are traditionally hand-connected, point by point from the PLC to the field terminal block or interface board. Using standard prewired and pretested cables and connectors, Interfast can increase wiring speed up to 20...

By Staff
Dedicated Controls March 1, 1998

How to Control Processes with Large Deadtimes

Processes with large deadtimes present a special challenge for a controller—any controller. The controller must wait until the deadtime has passed before it gets any feedback from the process.The best thing to do for controlling this type of process is to try to reduce the dead time. Simply moving a probe closer to the valve may do it.

By John Gerry, ExperTune
Dedicated Controls March 1, 1998

U.K.-based Eurotherm plc Acquiring Action Instruments

Action Instruments Inc. announced Feb. 6 that it is being acquired by U.K.-based Eurotherm plc, the world's largest manufacturer of industrial temperature controllers. Subject to FTC and shareholder approval, the purchase was expected to be completed by the first week of March 1998.

By Staff
Dedicated Controls March 1, 1998

The British Invasion

One if by land; two if by sea! It may not have been what our forefathers had in mind, but U.S. control companies should take note. The British are coming.In February, two independent automation suppliers, both located in California, were acquired by companies in the U.K.On February 6, Action Instruments, a $20 million supplier of signal conditioners, announced its acquisition by Eurotherm...

By Jane S. Gerold
Dedicated Controls March 1, 1998

Basics of Proportional-Integral-Derivative Control

A feedback controller is designed to generate an output that causes some corrective effort to be applied to a process so as to drive a measurable process variable towards a desired value known as the setpoint. The controller uses an actuator to affect the process and a sensor to measure the results.

By Vance J. VanDoren
Dedicated Controls March 1, 1998

DCS/PLC System Simultaneously Upgrades Plant, Cuts Costs

To do more with less is not an easy challenge. Luckily, some timely assistance is exactly what engineers at Engelhard Corp. (Attapulgus, Ga.) received recently when they sought to replace outdated control systems and reduce overall costs at their petroleum catalysts production plant.Engelhard's staff was working to cut costs by $7 million per year, but also knew they had to replace the pl...

By Staff
Dedicated Controls March 1, 1998

Tuning Fundamentals: Basics of Proportional-Integral-Derivative Control

PID controllers are by far the most popular feedback controllers for continuous processes. Here's a look at how they work.

By Vance J. VanDoren