Transducers are widely used for measurement purpose. There are various types of transducers available in the market. Today, we will learn about what are the photoelectric transducers.
PHOTOELECTRIC TRANSDUCERSare the transducers which converts light energy into electric energy for measurement purposes. The light waves are thrown at the devices and electric current is produced due to this.
Photo electric transducers are mainly classified as: –
- Photo emissive
- Photo-conductive
- Photo-voltaic
PHOTO EMISSIVE TRANSDUCER works on the principle that when the light falls on its cathode it causes the electrons to emit from the cathode
electrodes. By using number of cathodes, we can multiply these electrons which can be transferred to anode causing an electric current to flow.
These electrons strike the other cathode at very high velocity and releases the electrons from the cathode on which it is striking. Thus a great amount of electricity starts to flow which can be used for measurement purpose. This action can be said as amplification as the current increases at a very high rate. The only disadvantage is that if this transducer near a magnetic field, the emission of electrons may get affected which can be troublesome to measure the light.
PHOTOCONDUCTIVE CELLS are the type of transducers in which the light is made to fall on the device and the resistance of that transducer element changes which allows the current to flow through it. The higher the illumination, the lesser is the resistance offered by the device. Thus, the name photoconductive cells.
The change in resistance depends on the type of material used. Mostly, materials such as Cadmium sulphide, Cadmium Selenide or Cadmium sulpho-selenide.
This type of transducer requires an additional supply of voltage for control purposes.
PHOTOVOLTAIC CELLS are the type of transducers which produces an electric current to flow through the circuit when it is strikes by light. These cells produce energy using light rays. These cells are widely used in generation of electricity but can be used for measurement purposes also. The material used for these cells are Silicon, selenium and gold-doped germanium.
Reference: –
- Adapted from ELECTRONIC INSTRUMENTATION by H S KALSI