communications between computers and various I/O devices (peripherals) such as electric typewriters,
printers, plotters and VDUs. Serial transmission is relatively slow and fast data processing is better
accomplished using parallel transmission, provided that the distance between the various devices does
not exceed a metre or so. A typical interfacing arrangement is shown in Figure 13.4.
13.4—
The Scope of Microprocessor Control and Computers in Analytical Laboratories
Because of the increasing importance of both microprocessors and computers in analytical chemistry,
analytical chemists need an appreciation of their scope and limitations.
Most instrumental parameters can now be set and monitored continuously under the control of a
microprocessor and employing a limited amount of memory. This facilitates the running of repetitive
analyses with improved precision (although not necessarily with improved accuracy) and unattended
operation which releases the analyst for other duties. An example of the degree of control available in a
modern instrument is shown in Figure 13.5.
For laboratories or groups of laboratories where computerized instrumentation is going to make a major
contribution, the choice between a relatively large computer linked to many instruments and a series of
mini-or microcomputers each dedicated to a single instrument or small group of instruments has to be
made. Complex analytical instruments such as mass spectrometers and FT-NMR spectrometers will
continue to require their own dedicated computer to perform specialized data-handling routines. The
increasing power of microcomputers will enable more sophisticated data reduction and storage to be
accomplished by individual instrument-computer combinations. However, there still remains the need
for mass data storage such as in libraries of chromatograms or spectra or for quantitative results, for the
overall management of large laboratories using a LIMS and for communication between groups of
laboratories, possibly dispersed throughout the world. These applications require large mini-and
mainframe computers and a time-sharing system if individual instruments are to be interfaced. It must
be recognized, however, that a central computing facility, whilst attractive in terms of standardization,
ease and speed of communication and access to large data banks, can be inconvenient, if not disastrous,
each time the computer or network goes down. This eventuality is by no means uncommon and
strengthens the case for a series of powerful microcomputers with dedicated tasks and independent of
each other's transient operating problems. Local area networks (LANs) facilitate communication and
data transfer between a group of instruments and microcomputers and allow them to access a
mainframe computer when necessary.
The following examples are intended to illustrate some of the current capabilities of instruments under
microprocessor control or interfaced to a dedicated microcomputer. These capabilities are becoming
more sophisti-