Page 11 - Instrumentation and Measurement

The term analogue is therefore used to indicate systems where there is continuous representation of
a variable quantity. Most traditional gauges, meters and clocks are in this category.

1.8 Digital

A digital device manipulates 'bits', that is, discrete items of information - illustrated by the digital
clock representation. States are on/off, equal/unequal, etc. and the binary digit system is utilised.

1.9 Computers

Electronic analogue computers are essentially simulators on which electrical analogues of various
systems can be analysed and illustrated.
The digital computer is a machine for routine, high-speed repetitive arithmetic.

1.10 Microprocessors and Microcomputers

First-generation mainframe computers (approx. room size) were often, for the same capacity,
replaced by minicomputers (say desk size) and in turn by microcomputers (hand size and smaller)
following the silicon chip and integrated circuit (IC) development.
A microprocessor (P) - component product - may be a single chip unit or a collection of
unassembled processor-related components such as central processor unit (CPU), timers, memories,
interfaces, etc.
A microcomputer (CP) - board product - assembly of up components mounted on a printed circuit
board is sufficient to make up a working computer.
Beside the microprocessor other critical functions are input/output buffers, random access memory
(RAM) and read only memory (ROM).
While the P, consisting of arithmetic logic units plus sets of registers and control circuits, cannot
be used by itself to create a system, it can with support from a dedicated controller or CP. The P
is applied to Instrumentation and Control in the form of the Programmable Logic Controller (PLC).

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