Sensor - The Electronic Nose Artificial Olfaction Technology - page 48

- Buoyancy method
- Vibrating level systems
• Hydrostatic pressure methods
- Differential pressure level detectors
- Bubbler systems
• Electrical methods
- Conductivity probes
- Capacitance probes
- Optical level switches
- Ultrasonic level detectors
- Microwave level systems
- Nuclear level systems
Units:
It is expressed in terms of pressure the column exerts over a datum level or the
length of the liquid column.
2.4.5 Electrochemical Sensor
Electrochemical sensors operate by reacting with the gas of interest and producing
an electrical signal proportional to the gas concentration. A typical electrochemical
sensor consists of a sensing electrode (or working electrode), and a counter
electrode separated by a thin layer of electrolyte. A schematic of capacitive sensor
is shown in Fig. 2.11 .
Electrochemical sensors require very little power to operate. Their power
consumption is the lowest among all sensor types available for gas monitoring. So,
the sensors are widely used in portable instruments that contain multiple sensors.
They are the most popular sensors in confined space applications. A sensor's life
expectancy is highly dependent on the environmental contaminants, temperature,
and humidity to which it is exposed.
Fig. 2.11 Schematic
capacitive sensor