Chapter 6 Gamal

5/22/2018 Chapter 6 Gamal

1/25

TRANSDUCERS

Dr. Gamal Sowilam

1


2/25

IntroductionInput device

Output device

measurement and delivers a proportional electrical

.

The signal is amplified, filtered, or modified to an

.

The output device will display and record the

2

.


3/25

Introduction (contd)

nonelectrical.

electrical signal in order to use electrical methods and

, , .

A transducer is a device actuated by energy in one

form or in another form to a second transmission

s stem.

3


4/25

Types of Transducerelectrical principles involved:

Self-Generating Transducers

electrical parameter which can be measured as a

Self-Generating transducers produce an analog

form of energy. They do not require external power.

4


5/25

Ex: Potentiometric device, Resistance strain gage, thermistor

and photoconductive cell.

Capacitance Transducer

Ex: Variable capacitance pressure gauge, Capacitor

microphone and Dielectric gage. Inductance Transducer

Ex: Magnetic circuit transducer, Differential Transformer and Eddycurrent gage.

Ex: Hall effect pickup, Ionization chamber and Photoemissive

cell.

5


6/25

-

Application: Temperature, heat flow and radiation.

Application: Velocity and vibration.

Application: Sound, vibration, acceleration and pressure

changes.

Photovoltaic cell

Light meter and solar cell.

6


7/25

Resistance Transducers

Rotary and slider types of variable resistance

and a variable contact which can be moved along and make

continuous contact with the track. If the track resistance is proportional tothe length along the track

(i.e. linear track), the output voltage will be proportional to the

7

movemen o e var a e con ac an e un s su a e or use as

a position transducer.


8/25

8


9/25

9


10/25

10


11/25

Inductive Instrumentations

1 Transducer for Linear Position/Force(LVDT)

Consisting of three coils mounted on a

common former and having a magnetic

core that is movable within the coils.

supplied from an A.C. supply and the coilson either side are secondary coils and are

a e e .

Coils A & B have equal number of turns

and are connected in series opposing sothat the output voltage is the difference

between the voltages induced in the coils.

11


12/25

2. Tachometer

12


13/25

13


14/25

.

This transducer used for

fluids that is good connected to

electricity in tubes. The tube is

14


15/25

Capacitive Instrumentations

This type of instrumentations depends upon on the distance between

15

.


16/25

1. Rotational movement transducer

2. Linear movement transducer

16


17/25

3. Pressure transducer

17


18/25

Temperature TransducerThe temperature Instrumentations can classify into:

. .

2. Thermo Couple.

3. Thermostat.

1. Resistance Thermometer

18


19/25

19


20/25

2. Thermocouple

20


21/25

3. Thermistor

21


22/25

Temperature Transducer

Platinum RTD (Resistance Temperature Dependent )

Consistin basicall of a thin film of latinum de osited on a ceramic

substrate and having gold contact plates at each end that make contact

with the film. The resistance of the film increases as the temperature increases, i.e. it

has a positive temperature coefficient.

22


23/25

Transducer for Light Measurement

Photovoltaic Cell

Consisting basically of a two layer silicon device.

When light falls on the junction of the two materials, a voltage is developed with theN-type materia positive wit respect to t e P-type.

The output voltage depends on the magnitude of the light falling on the device and is

a maximum of the order of 0.6 V. With a load resistance connected to the out ut a

23 current will flow.


24/25

24


25/25

Piezoelectric Transducer

25

Chapter 6 Gamal

Documents

Transcript of Chapter 6 Gamal