60th Anniversary: CE History from 60, 30 and 15 years ago on pulses, controllers, pneumatics
Happy 60th, Control Engineering! Help us celebrate by looking at issues from 60, 30, and 15 years ago. Control Engineering magazine first published in September 1954. This monthly column in 2014 will review coverage in issues 60 (or 59), 30, and 15 years ago. While technologies have progressed since then, topics below (pulses, computers and controllers, and pneumatic control) remain relevant today.
July 1955: What pulses can do for you
An electronic pulse is a rapid surge or variation in voltage (or current). It is a discrete unit: a single signal with a beginning and an end. Characteristically, it is of relatively short duration on the time base being considered.
A pulse can assume several shapes, including a half sine wave or a crude square. But because of its relatively short duration it is commonly designated by a vertical line of no time dimension-a pip. Its shape is usually determined by the way it is generated and by the input requirements for the equipment that it must trigger or control.
In most systems, pulses and pulse handling equipment process data, compute, and control. Pulses have several inherent advantages that help them perform these functions. One is range. Pulses can be triggered at pushbutton rates or at high megacycle frequencies. Other advantages include precision, serving as a direct analog of binary numbers, and logical analysis.
July 1984: Editorial—Manufacturing or process plant automation: Computers and controllers must share data
The problem that must be addressed is that few "intelligent" devices can talk to each other. Data measured for one purpose can't be shared for a higher purpose, and this is a necessary feature of any system for plant-wide automation. Large firms, such as General Motors (GM), need it, but so does everyone else. The difference is that GM has the market clout to make control manufacturers listen, and everyone else stands to benefit. "In the next five years, GM will spend hundreds of millions of dollars on applied technology," said Ron Floyd of GM. Some 15 different GM divisions are participating in its Manufacturing Automation Protocol program, designed to force a de facto local area network (LAN) standard so that manufacturing plants can get on immediately with their urgently needed automation programs.
But control LANs aren't only for automation of discrete parts manufacturing. Control systems regulating different parts of continuous processes need to share information, too, if plant-wide automation is to be accomplished.
July 1999: Pneumatic control: Not dead yet
Pneumatic control may be considered a dinosaur, but it is still walking this Earth very much alive. Pneumatics has remained active in many process industries, even though it now often shares the spotlight in hybrid analog control systems. Even though control has slowly edged its way into the digital era, it has adapted to newer surroundings. The death knell has not yet sounded.
The cry for smaller, faster, cheaper control components and systems has driven much of the technology that is available to the process industries today. However, when an old standby like pneumatic control refuses to die, there must be some inherent advantages that rival newer technologies.
Although pneumatic components are not known for their small size, pneumatic transmitters, controllers, indicators, recorders, and panel-mount instruments are not as pricey as their electronic counterparts. Owing partially to their well-established technology and relatively simple mechanical construction, pneumatic instruments have remained solidly entrenched in many industries.
- 2014 edits, to fit this page, by Jordan M. Schultz, associate content manager, CFE Media.
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