Sensor - The Electronic Nose Artificial Olfaction Technology - page 41

Table 2.4 Types of pressure sensors
Sensory type Limits of application Advantages Disadvantages

Bourdon (C) Up to 100 MPa Low cost with reasonable

accuracy
Wide limits of application

Hysteresis
Affected by shock and
vibration

Spiral
Helical
Bellows Typically vacuum to

500 kPa

Low cost
Differential pressure

Smaller pressure range of
application
Temperature compensation
needed

Diaphragm Up to 60 kPa Very small span possible Usually limited to low

pressures

Resistive/strain
gauge

Up to 30 kPa Large range of pressures Sensitive

Piezoelectric - Fast dynamics Sensitive to temperature

changes

Fig. 2.8 Pressure scales

calculations and is distinguished from gauge pressure by putting ''abs'' after the
unit.

Absolute pressure ¼ Gauge pressure þ Atmospheric pressure

Differential pressure: This term is used to describe the difference between two
absolute pressure values, such as the pressures at two different points within the
same fluid (often between the two sides of a flow restrictor in a system measuring
volume flow rate).
In many cases, the absolute pressure is not the quantity of major interest in
describing the pressure. The atmosphere of gas that surrounds the earth exerts a
pressure, because of its weight, at the surface of the earth of approximately 14.7
psi. If a closed vessel at the earth's surface contained a gas at an absolute pressure
of 14.7 psi, then it would exert no effective pressure on the walls of the container
because the atmospheric gas exerts the same pressure from outside. In this case, it