In this topic, you study the difference between active and passive transducers.
Active Transducers
They do not require external power to operate. The energy required to generate output signal is obtained from the physical quantity being measured. Therefore, they are known as self-generating transducers. They generate an equivalent electrical output signal (voltage or current), which is the measure of physical quantity being measured.
For example: Thermocouples for Measurement of Temperature, Photovoltaic Cell for Measurement of Light Intensity, Piezoelectric Crystals for Measurement of Force, Mcleod gauge for Measurement of Pressure, etc.
Passive Transducers
They require an external source of power for their operation. Therefore, they are known as power operated transducers. The output signal is in electrical form. This output is a measure of variation in resistance, inductance and capacitance.
For example: LVDT, Hot wire anemometer, Pirani Gauge, etc.
The difference between active and passive transducer in tabular form as
| Active transducer | Passive transducer |
| It operates under energy conversion techniques. | It operates under energy controlling principles. |
| It doesn’t require an external power. | It requires an external power for its operation. |
| It is self-generating. | It is externally power operated. |
| It generates equivalent output signal without any energizing source. | Here, measurand is converted into passive parameter, such as, resistance or capacitance which needs external energy source so as to generate an equivalent output signal. |
| Examples: Thermocouple, Photovoltaic cell, Mcleod gauge | Examples: LVDT, Hot wire anemometer. |