sensors and transducers by d patranabis pdffree download

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I need the pdf of that book sensors and actuators

Sensors and Transducers

Simple stand alone electronic circuits can be made to repeatedly flash a light or play a musical note, but in order for an electronic circuit or system to perform any useful task or function it needs to be able to communicate with the “real world” whether this is by reading an input signal from an “ON/OFF” switch or by activating some form of output device to illuminate a single light.

This is a really good question. In today's world, both these terms are used in various contexts interchangeably. When I started Transducer Engineering in my sophomore year, my professor used to use the term 'sensor' for a particular element in today's class and he would call the same a 'transducer' in tomorrow's class. They both are widely used for the purpose of measurement. Let me start by giving some definitions.

Sensor - As the term suggests, it is a body which reacts to a physical, chemical or biological condition. It senses. It can be considered as a detector.
Transducer - The conversion of energy from one form to another is known as Transduction. A transducer serves for this purpose.

Now why there is confusion is that,
A Sensor can sense in any form(usually electronic) i.e due to some mechanical change, it can react in electrical form. Thus there is a conversion, similar to that of a transducer.
A classic example would be a thermocouple. Or a pressure sensor which might detect pressure and convert it into electric current (3-15psi to 4-20ma)

A Transducer is more than a sensor. It consists of a sensor/actuator along with signal conditioning circuits.
A signal conditioning circuit, by the name is a circuit which conditions the signal so that it is strong enough for further processing. A system might contain many stages before the signal finally reaches its destination to derive meaningful information.

A transducer is a device that converts one form of energy to another. Usually a transducer converts a signal in one form of energy to a signal in another.[1]
Transducers are often employed at the boundaries of automation, measurement, and control systems, where electrical signals are converted to and from other physical quantities (energy, force, torque, light, motion, position, etc.). The process of converting one form of energy to another is known as transduction.[2]

Transducer types

Active

Active sensors require an external power sources to operate, which is called an excitation signal. The signal is modulated by the sensor to produce the output signal. For example, a thermistor does not generate any electric signal, but by passing electric current through it, its resistance can be measured by detecting variations in current and/or voltage across the thermistor.[3][2]

Passive

Passive sensors generate electric signals in response to an external stimulus without the need of an additional energy source. Such examples are a thermocouple, photodiode, and a piezoelectric sensor.[4]
Sensors[edit]
A sensor is a device that receives and responds to a signal or stimulus.[5] Transducer is the other term that is sometimes interchangeably used instead of the term sensor, although there are subtle differences. A transducer is a term that can be used for the definition of many devices such as sensors, actuators, or transistors.[6][2]

Actuators

An actuator is a device that is responsible for moving or controlling a mechanism or system. It is operated by a source of energy, which can be mechanical force, electrical current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input.[2]

Bidirectional

Bidirectional transducers convert physical phenomena to electrical signals and also convert electrical signals into physical phenomena. Examples of inherently bidirectional transducers are antennae, which can convert conducted electrical signals to or from propagating electromagnetic waves, and voice coils, which convert electrical signals into sound (when used in a loudspeaker) or sound into electrical signals (when used in a microphone). Likewise, DC electric motors may be used to generate electrical power if the motor shaft is turned by an external torque.[2]