Instrumentation The Taylor Instrument Companies' contribution to the program was a talk on some aspects of the theory of process control, by J. G. Ziegler. Ziegler points out that a good deal can be done to many processes to make them more easily con trollable, and t h a t an understanding of the effects of load changes in any process is necessary for the design of a good control system. He discusses methods for determining experi mentally the best settings for controllers using the response curve of the system. In an analysis of control of light ends fractionation E. D. Mattix of Cities Service Corporation discussed the control of fractionating equipment, known in petroleum refining circles as a debutanizer. He gives the liquid-vapor equilibrium dia gram for the n-butane-n-pentane system and also shows the liquid composition for each tray in the tower. The latter dia gram indicates that, to control this column, the temperature should be measured on the ninth tray rather than at the top or bottom. Mattix then goes on to describe two complete methods of controlling the operation of the debutanizer. J. B. McMahon and R. W. Landon of Republic Flow Meters Company spoke on the control of primary operating variables. They emphasized the fact that one must exercise considerable judgment in applying mathematical methods to instrumentation, since the neglect of what appear to be un important details may lead to completely erroneous results. They analyzed problems in flow, temperature, liquid level, and pressure control to demonstrate their point. Winfield B. Heinz of Penn Industrial Instrument Corpo ration is an exponent of pneumatic circuits for measurement and control. Few people are aware that pneumatic circuits are closely analogous to electronic circuits. Pneumatic relays can be used in suitable circuits in much the same way that vacuum tubes are used in electronic circuits. The author of this paper tabulates the analogous properties of pneumatic and electric circuits, and describes a group of useful pneu matic circuits. Much has been written on valve characteristics. At this symposium T. B. Burris of Fisher-Governor Company gave the subject a new twist in a paper entitled "The Relations of Valve Characteristics," in which he describes the many de tails of valve design which can completely destroy the desired equal percentage characteristic of a valve. Valve body de sign, stem and packing-gland design, and the design of the diaphragm motor all are important if the valve is to have an equal percentage characteristic. The final paper on the program was by D . M. Considine of the Brown Instrument Company on measurement as a factor in process instrumentation. I t is a survey of primary measur ing devices. Because most of those attending the meeting were familiar with the more conventional primary measuring devices, the author chose to emphasize some of the newer, less frequently used, primary measuring elements. Among these are the Pirani gage and the ionization gage for measuring low pressures, instruments for automatically recording dew point, the polarograph, infrared and ultraviolet spectrophotom eters, and the x-ray spectrometer. Those in charge of the Texas A. & M. short course on instrumentation for the process industries, and those who contributed papers for the program, are to be congratulated for the excellent job they have done. Almost everyone who is interested in instrumentation will find much stimulating new information in these proceedings.
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