Data acquisition, computer-controlled

Digital computer systems are used in I C systems important to safety to perform functions of protection, data acquisition, computation, control monitoring and display. If properly designed, they can offer the advantages of improved reliability, accuracy and functionality in comparison with analog systems. The computer system... 

Time Systems, McGraw-HiU, New York, 1985 Hawryszldewycs, Database Analysis and Design, Science Research Associates Inc., Chicago, 1984 Kham-hata, Microprocessois/Microcomputers Architecture, Software, and Systems, 2d ed.. Whey, New York, 1987 Liptak, Instrument Engineers Handbook, Chilton Book Company, Philadelphia, 1995 Melhchamp (ed.), Real-Time Computing with Applications to Data Acquisition and Control, Van Nostrand Reinhold, New York, 1983. 

An extruder for a polymer was controlled by a microprocessor based data acquisition and control system. The CAMILE system (Control And Monitoring Interface for Laboratory Experiments) connects the sensors and control elements of the extruder to a host MS-DOS computer. While a variety of variables are measured and controlled, this paper will consider only temperature control. 

In order to represent and reason with temporal information, we need to represent time explicitly and concisely. The discrete-time character of computer-aided data acquisition and control dictates that time should be represented as a sequence of strictly increasing time points ... 

Figure 24.2 Schematic diagram of the setup used to measure and control H2O concentration and gas temperature in the combustion region (in situ) of a forced 5-kilowatt combustor at Stanford University 1 — steel duct 2 — quartz duct 3 — A1 duct 4 — multiplexed beam 5 — tunable diode lasers 6 — data acquisition and control computer 7 — control signals 8 — primary air driver Aair sin(27r/of) 9 — fuel drivers Afuei sin(27r/of-f dfuei) 10 — demultiplexing box 11 — Si detector (ND filter) and 12 — laser beam...

Figure 24.10 Schematic diagram of the combustion-control experiment at China Lake 1 — primary air 2 — primary air driver sin(27r/ot) 3 — pyrolysis gases N2 -h C2H4 4 — secondary air 5 — secondary air drivers sin(27r/ot- -0) 6 — demultiplexing box 7 — sampling probe 8 — multipass fast-sample cell (36-meter path) 9 — InGaAs detector 10 — multiplexed beam and 11 — data acquisition and control computer...

MICHAEL LEVIN is President and CEO, Metropolitan Computing Corporation (MCC), East Hanover, New Jersey, specializing in process analytical instrumentation as well as data acquisition and control systems for tablet presses, mixers, roller compactors, and other equipment. Prior to forming MCC in 1985, he was a consultant to pharmaceutical companies such as Merck, Sandoz, and Warner-Lambert. A member of the American Association of Pharmaceutical Scientists, the International Society for Pharmaceutical Engineering, and the Biomedical Engineering Society, Dr. Levin received the Ph.D. degree (1985) in biomathematics from the University of Washington, Seattle. 

The automation concept implemented at Conroe is called computer production control (CPC).2 CPC systems are driven by a general purpose process-control computer (48-K core memory) centrally located and programmed to monitor production and equipment operations and perform oil and gas accounting. As shown in Fig. 11, the computer is connected to a supervisory control system with a computer interface unit (CIU) to provide remote data acquisition and control function capability. 

The Type II system comes in two flavors. They vary by the type of gradient pumping system they contain low-pressure mixing or high-pressure mixing. The rest of the system is the same injector, variable detector, and computer-based data acquisition and control. Autosamplers would allow 24-hr operation, but most university research laboratories find graduate students to be less expensive. 

The state-of-the-art laboratories are equipped with the latest models of analytical instruments and computer systems, while others may have older, less sophisticated equipment or a mix of modern and outdated instruments. The goal of production laboratories is to analyze samples in the fastest possible manner. To be competitive, laboratories must have fully automated analytical systems allowing unattended sequential analysis of samples and computerized output of analytical results. Data acquisition computers, programmed with specialty software, control analytical instruments, collect the raw data, and convert them into analytical results. These computers are typically interfaced with the LIMS, which networks different laboratory sections into a single computer system and transforms analytical results into laboratory reports. 

Similar to GC instruments, HPLC instruments consist of an injection port, a separation column, a detector, and an instrument control/data acquisition computer. The use of liquid as a mobile phase influenced the design and construction materials of HPLC instrumentation elements. A sample extract or an aqueous sample is introduced into the separation column through an injection loop that can be programmed to receive various volumes of liquid (5 pi to 5 ml). 

Computer Hardware. The use of a computer for data acquisition and control is mandatory because of the clock frequency used by the Reticon array (20 kHz) and the volume of data that it is capable of outputting. A PDP-8e computer made by Digital Equipment Corporation, with 12 K words of memory was employed. 

BASIC, or Beginners Algebraic Symbolic Instruction Code, was developed by Kemeny63 as a "baby FORTRAN" for simple computers (e.g., minicomputers). BASIC does not wait for the whole user-written program to be finished, but compiled each typed line as soon as typed. It was ideally suited for a simple learning environment. Microsoft VISUAL BASIC is a GUI-interfaced version. Microsoft QUICK BASIC 4.5 is much better than FORTRAN embodiments in accessing instruments for real-time data acquisition and control. 

To maintain the production rate, product quahty, and plant safety requires a data acquisition and control system. This system consists of tenperature, pressure, liquid level, flow rate, and conposition sensors. Computers record data and may control the process. Modem chemical plants use program logic controllers (PLC) extensively. According to Valle-Riestra [20], instrumentation cost is about 15% of pinchased equipment cost for little automatic control, 30% for full automatic control, and 40% for computer control. 

Data Acquisition and Control System. Computer-based system that controls all parameters of HPLC instrument (eluent composition (mixing of different solvents) temperature, injection sequence, etc.) and acquires data from the detector and monitors system performance (continuous monitoring of the mobile-phase composition, temperature, backpressure, etc.). 

The heart of this facility is a refractory-lined reactor cylinder with 20 cm in-diameier and a total height of about 6.5 m. The internal refractory forms two concentric cylinders (each one of thickness 6.5 cm) with different thermal conductivity and wearing properties. Additionally, the reactor tube, the cyclone and the recycling line are protected with outside insulation in order to minimise heat losses. The gasifier components (raiser, cyclone and standpipe) are equipped with ten thermocouples (K-type) and pressure transducers. The thermocouples probes are connected to a computer based data acquisition and control system. In addition, the feed rates of gasification... 

The reactor system is automated with a computer HP 9816 and a data acquisition and control unit HP 3497A of Hewlett Packard. The programme a.o. checks if all variables are within preset safety limits. In case of emergency the programme switches the gas feed from H2 to N2 and stops the liquid feed. The key variables are the temperatures in the catalyst bed, the gas and the liquid inlet temperatures as well as the gas and the liquid outlet temperatures and fiirther the reactor pressure, the inlet and the outlet gas flow rates and the liquid feed flow rate. They are temporarily stored in the computer memory and later transferred on floppy disk. The temperatures at all other locations are monitored and recorded with a Philips PM 8237A multipoint data recorder. 

Real-Time Computing (with Applications to Data Acquisition and Control), Van Nostrand Reinhold Co. 

In this text the reader can find material related to computer-instrument-process communication, data acquisition and control, reliability of process control computer systems, management aspects of in-plant computer installations, and a large number of case studies. Additional general references on digital computers and their application in the real-time environment are the following ... 

In the preceding two sections we gave a brief description of a digital computer and its characteristics, of the associated peripherals, and of the I/O interface required for data acquisition and control. In this section we examine the various types of control loops that result when a digital computer is used as the main controller, as well as the necessary hardware components. 

G. Gauglitz, R. Goes, Photokinetic evaluation by microprocessor controlled fluorescence data acquisition, Comput. Enhanced Spectrosc. 2 (1984) 159. 

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