Microprocessors and Computers

Making use of the information from monitoring probes, combined with the storage and analysis capabilities of portable computers and microprocessors, seems the best method for understanding corrosion processes. Commercial setups can be assembled from standard probes, cables, readout devices, and storage systems. When these are coupled with analysis by corrosion engineers, the system can lead to better a understanding of in-plant corrosion processes. 

The use of computers and microprocessors (also known as programmable electronic systems [PES]) in process control continues to grow. They have brought about many improvements but have also been responsible for some failures. If we can learn from these failures, we may be able to prevent them from happening again. A number of them are therefore described below. Although PES is the most precise descnption of the equipment used, I refer to it as a computer, as this is the term usually used by the nonexpert. 

A detailed discussion of the application of digital computers and microprocessors in process control is beyond the scope of this volume. The use of computers and microprocessor based distributed control systems for the control of chemical process is covered by Kalani (1988). 

With the introduction of computers and microprocessor-controlled instrumentation, it has become possible to use spectrophotometry to obtain far more accurate determinations of color. The tristimulus values are obtained after integration of the data according to Eqs. (7)—(9). This degree of sophistication permits the use of more advanced methods of color quantitation, such as the 1976 CIE L u v system [41] or other systems not discussed in the present chapter. 

The management of an analytical chemistry laboratory involves a number of different but related operations. Analysts will be concerned with the development and routine application of analytical methods under optimum conditions. Instruments have to be set up to operate efficiently, reproducibly and reliably, sometimes over long periods and for a variety of analyses. Results will need to be recorded and presented so that the maximum information may be extracted from them. Repetitive analysis under identical conditions is often required, for instance, in quality assurance programmes. Hence a large number of results will need to be collated and interpreted so that conclusions may be drawn from their overall pattern. The progress of samples through a laboratory needs to be logged and results presented, stored, transmitted and retrieved in an ordered manner. Computers and microprocessors can contribute to these operations in a variety of ways. 

In most applications the low signal levels necessitate the use of signalaveraging techniques. A wide variety of multichannel analyzers, mini computers, and microprocessors suitable for this application are now commercially available. Frequently these devices must issue commands and/or receive information from parts of the spectrometer that are at elevated voltage levels, and this can best be achieved by means of optical coupling. 

The development and widespread use of computers and microprocessors in control laboratory instruments has made it possible to fully automate a laboratory, including interfacing instruments directly to a LIMS. In the fully automated laboratory, a sample is logged into a LIMS, then transferred to a laboratory where it is prepared for analysis by a robot, which then transfers it to an autosampler or analyzer. Once analyzed, the data is transferred through a communications link to a device which could convert the raw data into information that a customer needs. For example, in a simple case, a nmr spectrum could be compared to spectra on file to yield an identification of an unknown. In more complex instances, a data set could be compared to standards and by using pattern recognition techniques the LIMS would be able to determine the source of a particular raw material. Once the data is reduced and interpreted, the LIMS becomes the repository of the information. A schematic for such a fully automated laboratory is shown in Figure 2 (6). 

Jafarey et al. (61) derived a simple, approximate equation for binary distillation by simplifying the solution to Smoker s equation. Their equation is powerful for predicting the effect of disturbances on column performance. This makes their equation particularly useful in computer and microprocessor control, where it can be applied to estimate the effect of disturbances and the control action needed to compensate for them. This application is highlighted in Examples 3.8 and 3.9. The Jafarey et al, equation is... 

Secondly, rare metals have been mined, concentrated, and used in a variety of applications that find them interfacing with the human body in greater amounts. This has become increasingly so as the industrial era has changed into the communications era, with more and more of the rarer metals finding widespread use in semiconductors and other devices that drive the computers and microprocessors that we find increasingly in the equipment in our homes, offices, and motor cars. 

Conventional infrared spectrometers are known as dispersive instruments. With the advent of computer- and microprocessor-based instruments, these have been largely replaced by Fourier transform infrared (Fllk) spectrometers, which possess a number of advantages. Rather than a grating monochromator, an FTIR instrument employs an interferometer to obtain a spectrum. 

Subsequently Ishibashi and Fujinaga in Japan pursued a line of development based also on mechanical switching of potential, while in England Barker and coworkers built the first electronic instruments. The advent of solid-state electronics made possible broad commercial development of instruments which in turn extended pulse techniques to other electrodes and stimulated applications. Computer-and microprocessor-controlled instruments have expanded the use of pulse techniques and encouraged development of specialized waveforms. 

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