Instruments, microcomputer control

UV/visible 200-750 Cecil Instruments CE 594 (microcomputer controlled) Double High... 

Double beam spectrophotometers are being manufactured by various well-known manufacturers across the world, such as SUMADZU VARIAN CECIL BECKMAN PERKIN ELMER etc., to name a few. These instruments are mostly based on microcomputer-controlled devices with built-in recorder to accomplish faster speed and greater operating stability. 

In my lab we are constructing and testing autosamplers and microfraction collectors for CZE, both of which function under microcomputer control. Hjerten(25,26) has begun to explore the possibilities of gel-filled capillaries and of isoelectric focusing in capillaries. All of this work has as its goal a versatile and powerful instrumental version of electrophoresis complementary to modern HPLC. 

A microcomputer-controlled prototype instrument was described, and evaluated for its ability to correct for changes in relative humidity levels (89). The instrument incorporated crystal pairs coated with polyethylene glycol 400 or 1540 or tri-n-octylphosphine oxide and cobalt (II) chloride. It was shown that TDI can be detected over the range o.l - 15 ppm with relative humidities... 

Once a column has been chosen, the two variables which can be modified to optimise the separation of components are temperature and carrier gas flow-rate. The latter is often preset although the newer microcomputer controlled instruments allow the flow rate and temperature to be changed between runs for automatic optimisation. Accurate control of column temperature is important in order to obtain reproducible chromatograms. 

Careful calibration for sulphur is required using a range of standards to establish the response curve. Microcomputer controlled instruments can provide on board routines to produce a linear response based on a factor... 

Figure 8.6 Microcomputer controlled instrument with control, ADC and communications...

The trend in the 1980 s has shifted towards the development of microcomputer controlled voltammetry. Several reports have appeared in the literature where an inexpensive personal computer has been interfaced to a potentiostat (27). The most significant advantage of the microcomputer is that itnas made it possible for researchers to build their own instrumentation hardware, thus dispelling much of the mystery previously associated with... 

With the infusion of personal computers (PCs) into the workplace, several new companies have introduced systems controlled by PCs. For example, software is available from Delta Instruments to control experiments using an IBM-compatible microcomputer with a Cypress System potentiostat. A "mouse" is used to facilitate data... 

Microcomputer-based subsystems are standard in most computer control systems available today. The digital subsystems are interconnected through a digital communications network. Such systems are referred to as distributed digital instrumentation and control systems because of the network approach used to monitor and control the progress. 

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. 

T.F. Niemann, M.E. Koehler, and T. Provder, "Microcomputers Used as Laboratory Instrument Controllers and Intelligent Interfaces to a Minicomputer Timesharing System," in Personal Computers in Chemistry> p- Lykos, Ed,... 

The character and the degree of automation in chemical control may have been covered in the above treatment of semi-automatic or completely automatic, and of discontinuous or continuous analysis, but something more should be said about the means by which automation proper has been performed in recent times. Whereas in the past automated analysis involved the use of merely, mechanical robots, to-day s automation is preferably based on computerization in a way which can best be explained with a few specific examples. Adjustment knobs have been increasingly replaced with push-buttons that activate an enclosed fully dedicated microcomputer or microprocessor in line with the measuring instrument the term microcomputer is applicable if, apart from the microprocessor as the central processing unit (CPU), it contains additional, albeit limited, memory (e.g., 4K), control logics and input and output lines, by means of which it can act as satellite of a larger computer system (e.g., in laboratory computerization) if not enclosed, the microcomputer is called on-line. 

In 1976, Radiometer61 presented for the first time a microprocessor-controlled titration system. Since then, the microprocessor has been used preferentially and as a fully integrated part (in line) in electroanalytical instruments as a replacement for the on-line microcomputer used before. Bos62 gave a comprehensive description of the set-up and newer developments with microprocessors in relation to microcomputers and indicated what they can do in laboratory automation. Many manufacturers are now offering versatile microprocessor-controlled titrators such as the Mettler DL 40 and DL 40 RC MemoTitrators, the Metrohm E 636 Titroprocessor and the Radiometer MTS 800 multi-titration system. Since Mettler were the first to introduce microprocessor-controlled titrators with their Model DK 25, which could be extended to a fully automated series analysis via the ST 80/ST 801 sample transport and lift together with the CT 21/CT211 identification system, we shall pay most attention to the new Mettler MemoTitrators, followed by additional remarks on the Metrohm and Radiometer apparatus. 

A dedicated microcomputer is interfaced to the Instron instrument in order to collect the raw data. The microcomputer consists of an 8080A microprocessor, 32K bytes of memory, A/D converter, serial I/O for communication, parallel I/O for digital control and sensing, a real-time programmable clock, and vectored interrupt control. 

The distinction between mini - and microcomputers is becoming essentially one of size and price. Minicomputers, which use 16- or 32-bit words, had much larger memories than microcomputers and could be used for the control of several laboratory instruments on a time-sharing basis. However, microcomputers are becoming ever more powerful. Although some still use 8-bit words, 16-bit and 32-and 64-bit word machines are becoming stan-... 

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