Sensor - The Electronic Nose Artificial Olfaction Technology - page 31

• Classification based on Application:

- Industrial process control, measurement, and automation.
- Non-industrial use—Aircraft, Medical products, Automobiles, Consumer

electronics, and other types of sensors.
• Classification based on power or energy supply requirement:

- Active Sensor—Sensors that require power supply are called as Active Sen-
sors. Example: photoconductive cell, Thermistor, Strain Guage, Capacitive
and inductive sensor, etc.
- Passive Sensor—Sensors that do not require power supply are called as
Passive Sensors. Example: Radiometers, Thermocouple, Piezo electronic, etc.
• Classification based on Measurand contact:

- Contact sensor: a sensor that requires physical contact with the stimulus.
Examples: strain gauges, most temperature sensors.
- Non-contact sensor: requires no physical contact. Examples: most optical and
magnetic sensors, infrared thermometers, etc.
• Classification based on specifications:

- Accuracy
- Sensitivity
- Stability
- Response time
- Hysteresis
- Frequency response
- Input (stimulus) range
- Resolution
- Linearity
- Hardness (to environmental conditions, etc.)
- Cost
- Size, weight
- Construction materials
- Operating temperature, etc.

Elemental transduction processes (ETPs) mechanisms fall into four quite dis-
tinct types: energy conversion (C), energy dispersion (D), energy modulation (M),
and property modulation (P). Classification of sensory technology by measurand
category is shown in Table 2.1 [ 2 ].

2.4.1 Temperature Sensor

The word temperature was coined to describe the degree of hotness or coolness of
a material body. All temperature sensors have nonlinear transfer functions,
exceptional is IC sensors. Sensor outputs may be well digitized directly by high