Sudan University of Science and Technology College of Graduate Studies Department of Electrical Engineering

Sensors: 
A sensor is a device that detects and responds to some type of input from 
the physical environment. The specific input could be light, heat, motion, 
moisture, pressure, or any one of a great number of other environmental 
phenomena. The output is generally a signal that is converted to human-readable 
display at the sensor location or transmitted electronically over a network for 
reading or further processing. 
Sensor is a device that when exposed to a physical phenomenon 
(temperature, displacement, force, etc.) produces a proportional output signal 
(electrical, mechanical, magnetic, etc.).The term soften used synonymously with 
sensors. However, ideally, a sensor is a device that responds to a change in the 
physical phenomenon. On the other hand, a transducer is a device that converts 
one form of energy into another form of energy. Sensors are transducers when 
they sense one form of energy input and output in a different form of energy. For 
example, a thermocouple responds to a temperature change (thermal energy) and 
outputs a proportional change in electromotive force (electrical energy). 
Therefore, a thermocouple can be called a sensor and or transducer [15]. 
Classification: 
Table 4.1 lists various types of sensors that are classified by their measurement 
objectives. Although this list is by no means exhaustive, it covers all the basic 
types including the new generation sensors such as smart material sensors, 
micro-sensors, and Nano-sensors [15]. 

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Table 4.1 Type of Sensors for Various Measurement Objectives (Continued)
Sensor 
Features 
Linear/Rotational 
variable 
differential 
transducer (LVDT/RVDT) 
Optical encoder 
Linear/Rotational sensors 
High resolution with wide range capability Very stable in static 
and quasi-static applications 
Simple, reliable, and low-cost solution Good for both absolute 
and incremental measurements 
Electrical tachometer
Hall effect sensor
Capacitive transducer 
Resolution depends on type such as generator or magnetic 
pickups
High accuracy over a small to medium range 
Very high resolution with high sensitivity 
Low power requirements 
Good for high frequency dynamic measurements 
Strain gauge elements 
Very high accuracy in small ranges 
Provides high resolution at low noise levels 
Interferometer 
Laser systems provide extremely high resolution in large 
ranges 
Very reliable and expensive 
Magnetic pickup 
Gyroscope 
Inductosyn 
Output is sinusoidal 
Very high resolution over small ranges 
Seismic accelerometer 
Piezoelectric accelerometer