Uses of Passive Transducers

Uses of Passive Transducers

Passive Transducers


  • A Thermocouple is used to measure temperature.
  • It works based on the principle that the voltage difference between two different metals can be related to temperature.
  • The SI unit of measurement for a thermocouple is usually degrees Celsius (°C) or Kelvin (K).

Light Dependent Resistor (LDR)

  • An LDR is a sensor used to detect changes in light intensity.
  • Its resistance decreases as the intensity of light increases.
  • LDRs are frequently used in light sensing circuits and devices, for example, in automatic street lighting.


  • A Thermistor can be used to measure temperature, similar to a thermocouple.
  • It is a type of resistor whose resistance is significantly affected by temperature.
  • In a Negative Temperature Coefficient (NTC) thermistor, resistance decreases as temperature increases.

Strain Gauge

  • A Strain Gauge is used to measure the strain (deformation) on an object.
  • When the object is deformed, the strain gauge also deforms, resulting in a change in its electrical resistance.
  • The change in resistance is measured and used to calculate strain.

Piezoelectric Sensor

  • A Piezoelectric Sensor is used to convert changes in physical parameters like pressure, strain or force into an electrical charge.
  • They are often used in touch-sensitive devices, microphone elements, and accelerometer sensors.

Photovoltaic Cell

  • A Photovoltaic Cell is used to convert sunlight into electric current using the photovoltaic effect.
  • It is a key device in solar power generation.
  • Their output depends on the intensity of incident light and the angle of incidence.


  • A Microphone is a transducer that converts sound waves into electrical signals.
  • The output voltage is proportional to the amplitude of the sound waves.
  • They are frequently used in a wide range of audio recording and broadcasting applications.

Remember, the term ‘passive’ in this context refers to the fact that these devices do not require an additional power source to perform their sensing function, as they generate their own output signal by modifying the characteristics of the input in response to the physical phenomenon they are measuring. As such, these passive transducers form vital links between the physical and electronic world, allowing us to monitor and control a wide range of parameters.