Sensor dan TransduserRudi Susanto

Definisi Sensor dan transduser

Sensor adalah suatu peralatan yangberfungsi untuk mendeteksi gejala-gejalaatau sinyal-sinyal yang berasal dariperubahan suatu energi seperti energilistrik, energi fisika, energi kimia, energibiologi, energi mekanik dan sebagainya

Contoh; Camera sebagai sensor penglihatan, telinga sebagai sensor pendengaran, kulitsebagai sensor peraba, LDR (light dependent resistance) sebagai sensor cahaya, dan lainnya.

Transduser adalah sebuah alat yang biladigerakan oleh suatu energi di dalam sebuahsistem transmisi, akan menyalurkan energi tersebut dalam bentuk yang sama atau dalam bentuk yang berlainan ke sistem transmisiberikutnya”. Transmisi energi ini bisa berupalistrik, mekanik, kimia, optic (radiasi) atau thermal (panas).

Skema Input Output Tranduser

Detectable PhenomenonStimulus Quantity

Acoustic Wave (amplitude, phase, polarization), Spectrum, Wave

Velocity

Biological & Chemical Fluid Concentrations (Gas or Liquid)

Electric Charge, Voltage, Current, Electric Field (amplitude,

phase,

polarization), Conductivity, Permittivity

Magnetic Magnetic Field (amplitude, phase, polarization), Flux,

Permeability

Optical Refractive Index, Reflectivity, Absorption

Thermal Temperature, Flux, Specific Heat, Thermal Conductivity

Mechanical Position, Velocity, Acceleration, Force, Strain, Stress,

Pressure, Torque

Choosing a Sensor

Sensor Block Diagram

• Blok diagram sensor

measurandPrimary

Transduction

Secondary

Transduction

Isyarat

input

Isyarat

output

Passive Sensor

• Mengkonversi sifat-sifat/isyarat fisik atau kimia ke dalam isyarat yang lain tanpa bantuan sumber energi

Contoh

Active Sensor

• Mengkonversi sifat-sifat/isyarat fisik atau kimia ke dalam isyarat yang lain dengan bantuan sumber energi

• Merupakan pilihan utama untuk isyarat-isyarat yang lemah/kecil

Active Sensor

• Blok Diagram Active Sensor

measurandPrimary

Transduction

Secondary

Transduction

Isyarat

input

Isyarat

output

Auxiliary Energy

Source

Analog Output

• Active sensor di industri elektronika mempunyai standar isyarat listrik baik analog (berupa tegangan atau arus) maupun digital

Digital Output

• Computer Based atau Microprocessor

Sensor dan Cara Kerjanya

Positional Sensors: potentiometer

16

Processing circuit

Can be Linear or Rotational

Positional Sensors: LVDTLinear Variable

Differential

Transformer

17

Positional Sensors: Inductive Proximity Switch

18

• Detects the presence of metallic objects (non-

contact) via changing inductance

• Sensor has 4 main parts: field producing Oscillator

via a Coil; Detection Circuit which detects change in

the field; and Output Circuit generating a signal (NO

or NC)Used in traffic lights (inductive loop buried under the road).

Sense objects in dirty environment.

Does not work for non-metallic objects. Omni-directional.

Positional Sensors: Rotary Encoders

19

• Incremental and absolute types

• Incremental encoder needs a counter, loses absolute

position between power glitches, must be re-homed

• Absolute encoders common in CD/DVD drives

Temperature Sensors

20

• Bimetallic switch (electro-mechanical) – used in

thermostats. Can be “creep” or “snap” action.

• Thermistors (thermally sensitive resistors); Platinum

Resistance Thermometer (PRT), very high accuracy.

Creep-action: coil or spiral that unwinds or coils with changing

temperature

Thermocouples

21

• Two dissimilar metals induce voltage difference (few

mV per 10K) – electro-thermal or Seebeck effect

• Use op-amp to process/amplify the voltage

• Absolute accuracy of 1K is difficult

22

Light sensors: photoconductive cells

23

• Light dependent resistor (LDR) cell

Light level sensitive switch

24

Photojunction devices

25

photodiodephototransistor

Photovoltaic Solar Cells

26

• Can convert about 20% of light power into electricity

• Voltage is low (diode drop, ~0.6V)

Solar power is 1.4kW/m^2

Photomultiplier tubes (PMT)

27

• Most sensitive of light sensors (can detect individual

photons)

• Acts as a current source

electrons

Motion sensors/transducers

28

• Switches, solenoids, relays, motors, etc.

• Motors

• DC

• Brushed/brushless

• Servo

• Stepper motors

• AC

Stepper motor

Brushed motor – permanent magnets on armature, rotor acts as electromagnet

Brushless motor – permanent magnet on the rotor, electromagnets on armature are

switched

Sound transducers

29

microphone speaker

• Note: voice coil can also be used to generate fast

motion

Piezo transducers

30

• Detect motion (high and low frequency)

• Sound (lab this week), pressure, fast motion

• Cheap, reliable but has a very limited range of

motion

Tugas!

1.Teori Pengantar Sensor2.Rangkaian Elektronika Sensor3.Prinsip Kerja4.Algoritma Program dalam

Implementasi