Sensor - The Electronic Nose Artificial Olfaction Technology - page 47

Fig. 2.10 Magnetic float
type level indicator

Table 2.8 Types of level sensors level sensors
Sensory type

Limits of
application

Advantages Disadvantages

Float Up to 1 m Can be used for switches Cannot be used with sticky fluids

which coat the float

Displacement 0.3-3 m Good accuracy Limited range

Cost of external mounting for high
pressures

Differential
pressure

No upper
limit

Good accuracy
Large range
Applicable to slurries with
use of sealed lines

Assumes constant density
Sealed lines sensitive to
temperature

Capacitance Up to 30 m Applicable for slurries

Level switch for many
difficult fluids

Affected by density variations

measurement and control operations. Figure 2.10 shows the level sensing in tank
measurement using magnetic float-type level indicator [ 17 ].
Level measurements are classified into two groups: direct methods and indirect
methods. A number of level sensing technologies are currently available, including
manometer, float method, ultrasonic, fluid pressure, RF capacitance, magneto
restrictive-based, and radar measurement systems. Various types of flow sensors
are summarizes in Table 2.8 .

Classification of Level sensors:

• Mechanical sensors

- Float methods