-
Instrumentation and Measurement Process Design and Control frontiers of measurement lie in increased resolution, stability, reliability, reduced size, and cost. All these are primarily engineering objectives. The forces of competition and ingenuity will meet these needs. In addition to these advances, however, we need, and hope for, some conceptual breakthroughs which will permit mass flow measurements, independent of composition and flow patterns, and without in-line energy absorption or erosion. Improved methods of making point, surface, and volume temperature measurements are also needed. The technique of acoustic resonance as a gage of volume is interesting. Is there a technique, suited to comxercial application, for arriving at the average‘ temperature of a continuously varying, but defined volume of liquid or gas by means of a single measurement? But regardless of whether the advances to be made are of an evolutionary engineering character, or of a revolutionary conceptual character-the key to measurements of the next decade will be improved dynamic response. I t will be the decade of dynamics. I n general, manometers must give way to diaphragms; thermocouples and their wells to conductance variations, for example; pneumatics to electronics; and indicating meters to logging, alarm, and recording systems.
THE
Data Handling Data will be transported about by means of electrical signals. It is immaterial whether they be current or voltage, force or position-balance null systems, or direct-indicating. The important and fundamental alternative is digital us. analog. There is no doubt that the bulk of calculations involving units, such as barrels of inventory, and dollars, and hours, will be performed with digital computers. It is equally apparent that most of the electronic cbntrollers which will be available commercially, for control of specific variables and the exercise for specific control actions, will be of an analog character. It appears reason-
-
able, therefore, to assume that control loops involving physical variables and actuators will utilize analog data, while business-control loops, or the bigger plant loops, surrounding the inner variable loops, will utilize a digital language. The uneertainties are many. How are we to translate effectively from one to the other? .Present electronic converters are too expensive. Engineers must, and will, come up w i q an inexpensive, fast, reliable, modular, analog-to-digital converter, and vice versa. Data systems will be developed which will have the capability of interrogating quiescent sensers periodically, comparing measured values against reference standards, alarming when appropriate, recording automatically during periods of trouble, and reproducing recorded performance at a later date. It is possible today, to record data from available transducers on magnetic tape; to replay this tape on any time base-thus reproducing the recorded phenomena in “fast” or “slow” motion, for detailed study. Operational data recorded on magnetic tapes can also, for research purposes, be applied to an analog-computer simulation of a process or a plant and thus the dynamic performance studied, process parameters modified, etc. .+
Automatic Control The last decade might be termed the childhood of automatic control. Continuous flow processes under automatic control are commonplace today. The big change which is sure to come in the adolescence of control is the introduction of sampled data control systems. Today’s control systems are designed, by and large, to act upon data supplied to them on a continuous basis, and they, in turn, exercise continuous control over final control elements such as valves. Sampled-data controllers will time-share theif internal organs, such as receivers, comparators, computers, and transmitters, by means of commutators, which will successively connect in sensers and corresponding final control elements.
Prologue to
The design of process control systems will become a more precise science, first as manufacturers characterize control components such as sensers and valves in terms of their mathematical transfer functions, and secondly as process research reveals and characterizes the dynamic behavior of processes and processing equipmelit. It is important to emphasize that new data gathering techniques, swh as the “slow-motion” magnetic tape playback, are an absolute must if the detailed data necessary to characterize the dynamics of the process-plant complex are to be gathered.
Systems Engineering We are at the first frontier of systems engineeridg. We haven’t even reached the Allegbenies. The greatest potential for systeme engineering lies in the concept of the development and operation of production centers in which the variables of the process and of the market are continuously-computer-directed operation. But before this can be achieved, we must and will see the development of
A. Better dynamic means of measurement and analysis. B. Completely new concepts of processing finlts, such as crushers, grinders, evaporators, heat exchangers, fractionating towers, condensers, etc., designed principally to maximize their dynamic response, and thus their controllability. Sonic techniques, radiation fields, electrostatic and electromagnetic separation, must find expression in commercially practical equipment. C. We must also: if systems engineering is to achieve its greatest potential. . . gain a better understanding of the economic dynamics of the business, and the market. This will involve mathematical models of the plant and market and their interrelatibnship, in which the variables will be b&iness measures, such as profits, efficiency, inventory, return on investment, and demand. ROBERT J. JEFFRIES Data-Control Systems Danbury, Conn. VOL. 51,
NO.
1
JANUARY 1959
*
9
