Sensor dan Transduser Rudi 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).
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
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
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
Positional Sensors: Inductive Proximity Switch
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• 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
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• 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
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• 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
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• 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
Photovoltaic Solar Cells
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• 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)
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• Most sensitive of light sensors (can detect individual
photons)
• Acts as a current source
electrons
Motion sensors/transducers
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• 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
Piezo transducers
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• Detect motion (high and low frequency)
• Sound (lab this week), pressure, fast motion
• Cheap, reliable but has a very limited range of
motion