sensors and transducers characteristics

1. Sensors and Transducers: Types and Characteristics

2. Sensor
A sensor is a device that detects and responds to physical stimuli from the environment, converting one
form of energy or physical quantity into another form that can be measured or processed. Sensors detect
changes in physical parameters such as temperature, pressure, light, motion, or chemical composition.
Transducer
A transducer is a device that converts one form of energy into another. It transforms energy from one
domain to another, such as mechanical to electrical, thermal to electrical, or optical to electrical. All
sensors are transducers, but not all transducers are sensors.
Fundamental Definitions

3. 1. Based on Power Source
Active Sensors
 Generate their own electrical signal without external power
 Self-powered devices that produce output signal from the measurand
 Examples: Thermocouples, piezoelectric sensors, photovoltaic cells
 Characteristics: No external power required, generally have lower sensitivity
Passive Sensors
 Require external power supply to operate
 Modify electrical properties in response to physical changes
 Examples: Thermistors, strain gauges, LDRs (Light Dependent Resistors)
 Characteristics: Higher sensitivity, require excitation voltage
Classification of Sensors

4. Based on Output Signal
Analog Sensors
 Produce continuous output signals proportional to input
 Output varies smoothly over a range of values
 Examples: Thermocouple, LVDT, potentiometer-based position sensors
 Characteristics: Infinite resolution, susceptible to noise, require ADC for digital systems
Digital Sensors
 Produce discrete output signals (binary or coded)
 Output in digital format directly
 Examples: Encoder, digital temperature sensors, proximity switches
 Characteristics: High noise immunity, direct interface with digital systems, limited resolution

5. 3. Based on Physical Parameter Measured
Temperature Sensors
 Thermocouples: Junction of dissimilar metals, generate voltage proportional to temperature difference
 RTDs (Resistance Temperature Detectors): Metal resistance varies with temperature
 Thermistors: Semiconductor resistance changes significantly with temperature
 IC Temperature Sensors: Integrated circuits providing calibrated temperature output
Pressure Sensors
 Piezoresistive: Resistance changes with applied pressure
 Capacitive: Capacitance varies with pressure-induced diaphragm movement
 Piezoelectric: Generate charge when subjected to pressure
 Optical: Use fiber optic principles for pressure measurement
Position and Displacement Sensors
 Potentiometric: Variable resistance with position
 LVDT (Linear Variable Differential Transformer): Inductive principle
 Encoders: Optical or magnetic, provide digital position feedback
 Capacitive: Capacitance varies with displacement

6. Velocity and Acceleration Sensors
 Tachogenerators: Generate voltage proportional to rotational speed
 Accelerometers: Measure acceleration using piezoelectric or capacitive principles
 Gyroscopes: Measure angular velocity and orientation
Force and Torque Sensors
 Load Cells: Convert force to electrical signal using strain gauges
 Torque Sensors: Measure rotational force using strain gauge or optical methods
 Piezoelectric Force Sensors: Generate charge proportional to applied force
Flow Sensors
 Differential Pressure: Measure flow through pressure drop
 Turbine Flowmeters: Rotational speed proportional to flow rate
 Ultrasonic: Use ultrasonic waves to measure flow velocity
 Electromagnetic: For conductive liquids using Faraday's law
Level Sensors
 Float-based: Mechanical float follows liquid level
 Ultrasonic: Time-of-flight measurement
 Capacitive: Dielectric constant changes with level