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TRANSDUCERS


A transducer is a device that converts one type of energy to another. The conversion can be to/from electrical, electro-mechanical, electromagnetic, photonic, photovoltaic, or any other form of energy. While the term transducer commonly implies use as a sensor/detector, any device which converts energy can be considered a transducer.

Briefly a transducer has to perform two major functions:

(1) To measure or sense a physical quantity in a measurement system
(2) To convert the measured value to a useful output







 Basic Requirements of a Transducer

(1)Accuracy and precision: Every transducer should follow an ideal or theoretical output/measured relationship. The accuracy of a transducer is defined as the ratio of the error to the full-scale output. Precision is the closeness with which measurements are distributed about their mean value.

(2) Repeatability : The transducer should reproduce same measured value when same input is applied consecutively under the same conditions in the same direction.

(3)Linearity : The input-output characteristics of the transducer should be linear. The transducers are designed with linear output/measured relationship as this tends to facilitate data reduction.

(4) Resolution : A transducer should possess both high resolution and high accuracy at the same time.

(5) Environmental Characteristics : When the transducer operates under the conditions which are different from the room conditions ,errors should not appear in the transducer output. In addition to this external forces should not affect the performance of transducer. Hence a transducer should not be affected by temperature, vibration and other external environmental condition.

(6)Dynamic Response : In case of input varying with time, the transducer should be able to respond to the changes in the input as quickly as possible.

(7) Ruggedness : It should be able to withstand overloads for short duration and adequate safety measures should be present for overload protection.


TRANSDUCER CLASSIFICATION

There is no standard way for the transducer classification but the following types of classification are most commonly used:

 Classification Based on application
a) Sensor
b) Actuator
c) Combination


(a) A sensor is used to detect a parameter in one form and report it in another form of energy (usually an electrical and/or digital signal). For example, a pressure sensor might detect pressure(a mechanical form of energy) and convert it to electricity for display at a remote gauge.
(b) An actuator accepts energy and produces movement (action). The energy supplied to an actuator might be electrical or mechanical (pneumatic, hydraulic, etc.). An electric motor and a loudspeaker are both transducers, converting electrical energy into motion for different purposes.
© Combination transducers have both functions; they both detect and create action. For example, a typical ultrasonic transducer switches back and forth many times a second between acting as an actuator to produce ultrasonic waves, and acting as a sensor to detect ultrasonic waves.