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controlled remotely or by a control system. Control instrumentation plays a significant role in
both gathering information from the field and changing the field parameters, and as such are a
key part of control loops.
Elements of industrial instrumentation have long histories. Some of the earliest
measurements were of time. One of the oldest water clocks was found in the tomb of the
Egyptian pharaoh Amenhotep I, buried around 1500 BCE. Improvements were incorporated
in the clocks. By 270 BCE they had the rudiments of an automatic control system device. In
1663 Christopher Wren presented the Royal Society with a design for a "weather clock". A
drawing shows meteorological sensors moving pens over paper driven by clockwork. Such
devices did not become standard in meteorology for two centuries.
In the early years of process control, process indicators and control elements such as
valves were monitored by an operator that walked around the unit adjusting the valves to
obtain the desired temperatures, pressures, and flows. As technology evolved pneumatic
controllers were invented and mounted in the field that monitored the process and controlled
the valves. This reduced the amount of time process operators were needed to monitor the
process. Later years the actual controllers were moved to a central room and signals were sent
into the control room to monitor the process and outputs signals were sent to the final control
element such as a valve to adjust the process as needed. These controllers and indicators were
mounted on a wall called a control board.
The transformation of instrumentation from mechanical pneumatic transmitters,
controllers, and valves to electronic instruments reduced maintenance costs. This also
increased efficiency and production due to their increase in accuracy. Pneumatics enjoyed
some advantages, being favored in corrosive and explosive atmospheres.
The pneumatic and electronic signaling standards allowed centralized monitoring and
control of a distributed process. The concept was limited by communication line lengths.
Each pipe or wire pair carried one signal. The next evolution of instrumentation came with the
production of Distributed Control Systems (DCS) which allowed monitoring and control from
multiple locations which could be widely separated. A process operator could sit in front of a
screen (no longer a control board) and monitor thousands of points throughout a large
complex. A closely related development was termed “Supervisory Control and Data
Acquisition” (SCADA). These technologies were supported by personal computers, networks
and graphical user interfaces.
Measurement instruments have three traditional classes of use:
monitoring of processes and operations;
control of processes and operations;
experimental engineering analysis.
While these uses appear distinct, in practice they are less so. All measurements have
the potential for decisions and control. A home owner may change a thermostat setting in
response to a utility bill computed from meter readings. In some cases the sensor is a very
minor element of the mechanism. Digital cameras and wristwatches might technically meet
the loose definition of instrumentation because they record and/or display sensed information.
Under most circumstances neither would be called instrumentation, but when used to measure
the elapsed time of a race and to document the winner at the finish line, both would be called
instrumentation.

Task III. Put as many questions as possible to the sentences.
1. A smoke detector is a common instrument found in most western homes. 2. One of the
oldest water clocks was found in the tomb of the Egyptian pharaoh Amenhotep I. 3. These
devices control a desired output variable, and provide either remote or automated control
capabilities.

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