The transducer may be defined as any device that converts energy from one form to another, Most of the transducers either convert electrical energy into mechanical displacement or convert some non-electrical physical quantities like temperature, Light, Pressure, Force, Sound, etc to an electrical signal. In an electronic instrument system, the function of transducers is of two types.

  1. To detect or sense the pressure, magnitude, and change in physical quantity being measured.
  2. To produce a proportional electrical signal.

Classification of Transducers

Passive Transducers

They required an external power supply and therefore the output is equal to the variation in a physical parameter such as pressure, temp, etc

  1. Thermistor
  2. Resistance Temperature Transducer

Self Generated Transducers

The self-generated transducers don’t use an external power supply source. However, they provide an electrical output when stimulated by some physical form of energy. The self-generated transducers are subdivided into many groups.

  1. Thermal Transducers

    Thermal transducers convert temperature changes into electrical signals. There are several types including thermocouples which use two dissimilar metals joined at one end that generate a voltage proportional to temperature. Thermistors are resistors made from semiconductor materials whose resistance varies significantly with temperature changes. Resistive temperature devices (RTDs) are resistors made from metals like platinum that increase resistance linearly with rising temperatures. Thermal transducers are used extensively for temperature measurement and control in industries like HVAC, food processing, chemical plants, automotive, aerospace, and more. They can measure over wide temperature ranges with good accuracy and repeatability.

  2. Optical Transducer

    Optical transducers convert light energy into electrical signals. Photoconductive devices change resistance when illuminated while photovoltaic cells generate a voltage proportional to light intensity. Photodiodes and phototransistors are common photoconductive devices with spectral responses matched to specific wavelengths. Solar cells are photovoltaic devices that convert sunlight directly into electricity. Optical sensors are used for remote sensing, position and motion detection, flame monitoring, smoke detection, and other automation tasks. Fiber optic sensors use light passing through optical fibers to measure temperature, vibration, pressure, and more. Optical transducers exploit light's speed and directionality for non-contact sensing over long distances.

    • Photo Conductive
    • Photo Voltic
  3. Mechanical Transducers

    Mechanical transducers convert physical phenomena like force, pressure, and displacement into electrical signals. Strain gauges measure strain on an object by changing resistance as the gauge stretches or compresses. LVDTs (linear variable differential transformers) detect linear displacement using transformer windings and a movable magnetic core. Load cells use strain gauges to measure weight or force. Accelerometers contain small proof masses that move under acceleration, enabling inertial sensing. Gyroscopes measure rotation and orientation. Tactile sensors measure touch, force, and pressure. Mechanical transducers are rugged, adaptable, and used widely in test & measurement, manufacturing, robotics, automotive, aircraft, and biomedical applications.

    • Strain Guage
    • Magnetic Transducers
    • LVDT Transducers