Transducer And It's Types

Transducer

An electrical transducer is a device which is capable of converting the physical quantity into a proportional electrical quantity such as voltage or electric current. Hence it converts any quantity to be measured into usable electrical signal. This physical quantity which is to be measured can be pressure, level, temperature, displacement etc. The output which is obtained from the transducer is in the electrical form and is equivalent to the measured quantity.

For example, a temperature transducer will convert temperature to an equivalent electrical potential. This output signal can be used to control the physical quantity or display it.

Note that any device which is able convert one form of energy into another form is called as a transducer. For example, even a speaker can be called as a transducer as it converts electrical signal to pressure waves (sound). But an electrical transducer will convert a physical quantity to an electrical one.

Types of Transducer

There are of many different types of transducer, they can be classified based on various criteria as:

Types of Transducer based on Quantity to be Measured :-

Temperature transducer (e.g. a thermocouple)

Pressure transducers (e.g. a diaphragm)

Displacement transducers (e.g. LVDT)

Flow transducers

Types of Transducer based on the Principle of Operation:

Photovoltaic ( e.g. a solar cell )

Piezoelectric

Chemical

Mutual Induction

Electromagnetic

Hall effect

Photoconductors

Types of Transducer based on Whether an External Power Source is required or not:

Active Transducer -

Active transducers are those which do not require any power source for their operation. They work on the energy conversion principle. They produce an electrical signal proportional to the input (physical quantity). For example, a thermocouple is an active transducer.

Passive Transducers -

Transducers which require an external power source for their operation is called as a passive transducer. They produce an output signal in the form of some variation in resistance, capacitance or any other electrical parameter, which than has to be converted to an equivalent current or voltage signal. For example, a photocell (LDR) is a passive transducer which will vary the resistance of the cell when light falls on it. This change in resistance is converted to proportional signal with the help of a bridge circuit. Hence a photocell can be used to measure the intensity of light.