Measurement Technology - The Electronic Nose Artificial Olfaction Technology - page 2

Measurement is necessary for proper operation, maintenance and control of
equipment and processes in manufacturing. Without the way for measurement,
automation would not be feasible.
In general, there are two major functions of all branches of engineering:

1. Design of equipment and processes and
2. Proper operation, control, and maintenance of processes.

Both these functions require measurements. It is through measurement that a
product can be designed or a process be operated with maximum efficiency,
minimum cost, and the desired degree of maintainability and reliability.

1.3 Measuring Systems

Measurement is generally made with instruments. Human sense can be very keen but
are lacking in range. Measurement can be viewed as the reconstruction of the input
from the observed output of an instrument. The input is measurand and the output is
the signal from the instrument. A measurement is considered to gather the specifi-
cations for accuracy, since a perfect measurement is not possible. Measurements
have been involved into every field of scientific activity from medicine to aerospace.
Figure 1.1 shows the functional states of measurement systems.

1. The physical medium refers to the object where a physical phenomenon is
taking place.
2. The sensor is affected by the occurrence in the physical medium either through
direct or physical contact or through indirect interaction of the observable fact
in the medium with several components of the sensing element. The first ele-
ment in any measuring system is the primary sensor: this gives an output that is
a function of the measurand (the input applied to it). Most commonly but not
for all sensors, this function is at least just about near to linear. Some examples
of primary sensors are a liquid-in-glass thermometer, a thermocouple, and a
strain gage. In the case of the mercury-in-glass thermometer, the output reading
is given in terms of the level of the mercury, and so this particular primary
sensor is also a complete measurement system in itself. In other sensors, a

Fig. 1.1 Functional states of measurement systems