Photoelectric transducer | Types of photoelectric transducer | Working and Construction

By | January 28, 2019

Transducer | Photoelectric transducer | Types of photoelectric transducer | Working and Construction

Hello friends, today in my this Post I will teach you about the photoelectric transducer, it’s types and working. So let’s start….!

Photoelectric transducer :

1) They are light sensitive detectors and convert a beam of light into electrical signals. The electrical signal can be in the form of a voltage generated, a change of resistance or electron flow in a circuit.

2) They can be electronic or solid state and can be classified based on their principle of operation as,
Types of Photoelectric transducer
1) photoemissive
2) Photoconductive
3) Photovoltaic

Also Read – Classification and types of transducer

Photoemissive Working and Construction :

1) It consists of a cathode and anode enclosed in an evacuated or inert gas filled tube. The cathode is made of oxidised silver base coated with a layer of cesium. Light, when strikes the cathode, causes the emission of electrons, which are attracted towards the anode. This produces a small current in the external circuit (Fig.) current produced is proportional to the intensity of light.

2) High gain type of photo emissive devices called photomultiplier tube use the principle of secondary emission. The arrangement consists of a series of reflecting electrodes called dynodes.

3) The electrons striking a dynode produce further emission of electrons. The arrangement serves to amplify the original output current. These types of transducers are useful for counting purposes.

Photoconductive Working and Construction :

1) It is a light controlled variable resistance. It is based on the principle that certain materials change their resistance when exposed to light. Increased intensity of light causes reduced resistance. Some light sensitive materials are, cadmium sulphide, cadmium selenide and doped

2) The cell consists of a thin layer of light sensitive material coated between two electrodes on a glass plate. In a circuit incorporating a photo conductive cell, current would vary depending on the intensity of light incident on the cell (Fig.). These are widely used for radiant measurements at all wavelengths.


Photovoltaic Transducer Working and Construction :

1) In this, a voltage is generated, when light is incident on it. It has a sandwich construction (Fig.) and consists (1) a metal base (2) a layer of semiconducting material (selenium) and (3) a thin transparent metal layer.

2) It is self generating and requires no external power other than light. They are widely used for exposure meters for measuring light intensity.

3) Photosensors can be designed to be sensitive not only in the visible spectrum but also in the infrared and ultraviolet range.

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