Question

Which among the following transducer is an example of active transducer?

• A. LDR (Light dependant sensor)
• B. Strain gauge
• C. Hall effect sensor
• D. Photovoltaic cell

Hint:

Active vs Passive Transducers. Active: Generate own electrical output (e.g., Thermocouple, Piezoelectric, Photovoltaic cell). Passive: Require external power/excitation; output is change in R, L, or C (e.g., Strain gauge, LDR, Thermistor, Capacitive/Inductive sensors).

Answer 1

The Correct Option is D

Transducers convert energy from one form to another for measurement purposes
They can be classified as active or passive: - Passive Transducers: Require an external power source (excitation signal) to operate
Their output is typically a change in a parameter like resistance, capacitance, or inductance
Examples: LDR (resistance changes with light), Strain gauge (resistance changes with strain), Thermistor (resistance changes with temperature), Capacitive sensor, Inductive sensor (LVDT)
Hall effect sensors also usually require an excitation current
- Active Transducers (Self-Generating): Generate their own electrical output signal (voltage or current) directly in response to the input measurand, without needing an external power source
Examples: Thermocouple (generates voltage due to temperature difference), Piezoelectric sensor (generates charge/voltage due to pressure/force), Photovoltaic cell (solar cell - generates voltage/current due to light)
Among the options: LDR and Strain gauge are passive (resistance change)
Hall effect sensors typically require excitation
Photovoltaic cells generate voltage/current directly from light energy and are active transducers