Transducers, Power Amplifiers, and Energy Converters

• Transducer: a low energy device that receives an input signal of one form and delivers another form of output signal relative to the input signal in a specified way

• Power Amplifier: a device with a relatively low energy input port that receives information that determines the bulk energy transfer from an integral power supply through the output port

• Energy Converter: a device which provides, between the two access ports, reversible exchange of bulk energy that does useful work without a separate power supply

Black Box Diagram

P1 P2+2

-

+1

-

Input Output

may be different types

Pressure TransducerTypical Construction uses a Diaphragm with a strain gauge

Rfq

+P-

+-

KpcR +

v-

i

+PC

-

Cr

Fluid Side Electric Side

Ideally, Rf = 0 Cf = 0

Ideally, Rf = 0 and Cf = 0They account for resistance to flow causing a pressure dropand C accounts for the change in the diaphragm

Power Amplifier

Stereo

i i

+v2

-

+v1

-wmw

ex: -CD player -Tape -Radio

ex: Servomotor+v1

-

iFieldControlled Servomotor

PowerSupply

IA= constant armature current

MechanicalLoad

P2P1

w Field Terminals

JmMech.Load

R

L+v1

-

i

P1 P2Bm

+w-

m

Kmi

ex: -tape drive motor -floppy disk drive motor -CD drive motor

electrical port input(low power)

mechanical port output(high power)

Ideal two-port subsystem Interfaces

SendingSubsystem

IdealInterface

ReceivingSubsystem

+1

-

+2

-

1 1

P1 P2

P1 = 11 = P2 = 22 (since ideal power in = power out)

Ex: * electric - electric * eletro - mechanical * rotational - linear

Ideal Two-Port Subsystem InterfacesTransformer Type Gyrator Type

1

2

1

2 = = a

1 2

2 1 = = P

P & a may or may not have dimensions depending on the interface subsystems

+v1

-

i

+v2

-

ia : 1

+1

-

+2

-

a : 1+1

-

+2

-

P

Generalized Generalized

Electrical

Dependent-source Models of the Ideal Transformer & Gyrator

+1

-

+2

-

a : 1+1

-

+2

-

P

+1

-

+2

-

P

+1

-

+2

-

P

+1

-

+2

-

a : 1

+1

-

+2

-

a : 1

+- +-

+-

+ -

Electric Transformer

N1

TurnsN2

Turns

+v1

-

i

P1

+v2

-

i

P2

Gear Train

P2

1 w1 2 w2

P1N1 Teeth

N2 Teeth

Lever

l1

l2

u2

f2

f1

u2

P1P2

Hoisting Drum

1 w1

r

f2 P2P1r = mean radius of drum

Armature Controller Motor

+v1

-

i

w

K = torque constant

P1 P2

+v-

+-

+u-

f1 : r+w-

KmiKmw M

Rotational toTranslationalInterface

IdealMotor

kv2Km

frok

Ideal+v1

-

i

w

+v-

i

+w-

Km : 1

+v-

i+w-

a : 1

+-Kmi

Kmw

v1

v2v3

w

= Kw + k

vi = w

More Realistic

Jm

L

+v1

-

Bm

Kmi+-

R

Kmw

i

+w-

Jm

L

+v1

-

Bm

R i

+w-