II) Electrical Transducers
Here are some of commonly used electrical transducers:
1) Potentiometers: They convert the change in displacement into change in the resistance, which can be measured easily.
2) Bridge circuits: These convert the physical quantity to be measured into the voltage.
3) Wheatstone bridge: It converts the displacement produced by the physical quantity to the current in the circuit.
4) Capacitive sensors or Variable Capacitance Transducers: These comprise of the two parallel plates between which there is dielectric material like air. The change in distance between the two plates produced by the displacement results in change in capacitance, which can be easily measured.
5) Resistive sensors or Variable Resistance Transducers: There is change in the resistance of these sensors when certain physical quantity is applied to it. It is most commonly used in resistance thermometers or thermistors for measurement of temperature.
6) Magnetic sensors: The input given to these sensors is in the form of displacement and the output obtained is in the form of change in inductance or reluctance and production of the eddy currents.
7) Piezoelectric transducers: When force is applied to these transducers, they produce voltage that can be measured easily. They are used for measurement of pressure, acceleration and force.
8) Strain gauges: When strain gauges are strained or stretched there is change in their resistance. They consist of the long wire and are able to detect very small displacements produced by the applied force or pressure.
9) Photo electric transducers: When the light is applied to these transducers they produce voltage.
10) Linear variable differential transformer (LVDT): LVDT is the transformer consisting of the primary and the secondary coil. It converts the displacement into the change in resistance.
11) Ultrasonic Transducers: These transducers use the ultrasonic or ultrasound waves to measure parameters like fluid level, flow rate etc.
Apart from these there are some more electrical type of transducers like moving coil type, changing dielectric type, changing core positions type etc.