Sensor dan Transduser. Rudi Susanto

Transkripsi

1 Sensor dan Transduser Rudi Susanto

2 Definisi Sensor dan transduser Sensor adalah suatu peralatan yang berfungsi untuk mendeteksi gejala-gejala atau sinyal-sinyal yang berasal dari perubahan suatu energi seperti energi listrik, energi fisika, energi kimia, energi biologi, energi mekanik dan sebagainya

3 Contoh; Camera sebagai sensor penglihatan, telinga sebagai sensor pendengaran, kulit sebagai sensor peraba, LDR (light dependent resistance) sebagai sensor cahaya, dan lainnya. Transduser adalah sebuah alat yang bila digerakan oleh suatu energi di dalam sebuah sistem transmisi, akan menyalurkan energi tersebut dalam bentuk yang sama atau dalam bentuk yang berlainan ke sistem transmisi berikutnya. Transmisi energi ini bisa berupa listrik, mekanik, kimia, optic (radiasi) atau thermal (panas).

4 Skema Input Output Tranduser

5 Detectable Phenomenon Stimulus Acoustic Biological & Chemical Quantity Wave (amplitude, phase, polarization), Spectrum, Wave Velocity 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

6 Choosing a Sensor

7 Sensor Block Diagram measurand Primary Transduction Secondary Transduction Isyarat input Isyarat output Blok diagram sensor

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

9 Contoh

10 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

11 Active Sensor measurand Primary Transduction Secondary Transduction Isyarat input Isyarat output Auxiliary Energy Source Blok Diagram Active Sensor

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

14 Digital Output Computer Based atau Microprocessor

15 Sensor dan Cara Kerjanya

16 Positional Sensors: potentiometer Can be Linear or Rotational Processing circuit 16

17 Positional Sensors: LVDT Linear Variable Differential Transformer 17

18 Positional Sensors: Inductive Proximity Switch Detects the presence of metallic objects (noncontact) 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. 18

19 Positional Sensors: Rotary Encoders 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 19

20 Temperature Sensors Bimetallic switch (electro-mechanical) used in thermostats. Can be creep or snap action. Creep-action: coil or spiral that unwinds or coils with changing temperature Thermistors (thermally sensitive resistors); Platinum Resistance Thermometer (PRT), very high accuracy. 20

21 Thermocouples 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 21

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23 Light sensors: photoconductive cells Light dependent resistor (LDR) cell 23

24 Light level sensitive switch 24

25 Photojunction devices photodiode phototransistor 25

26 Photovoltaic Solar Cells Can convert about 20% of light power into electricity Voltage is low (diode drop, ~0.6V) Solar power is 1.4kW/m^2 26

27 Photomultiplier tubes (PMT) Most sensitive of light sensors (can detect individual photons) Acts as a current source electrons 27

28 Motion sensors/transducers 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 28

29 Sound transducers microphone speaker Note: voice coil can also be used to generate fast motion 29

30 Piezo transducers Detect motion (high and low frequency) Sound (lab this week), pressure, fast motion Cheap, reliable but has a very limited range of motion 30

31 Tugas! 1.Teori Pengantar Sensor 2.Rangkaian Elektronika Sensor 3.Prinsip Kerja 4.Algoritma Program dalam Implementasi