1_pendahuluan
TRANSCRIPT
INTRODUCTION
BASIC CONCEPTS OF MEASUREMENT and
TRANDUCER CLASSIFICATION
BASIC CONCEPT
• Measurement: describing natural phenomena in quantitive terms
»Express in numbers
weight = 1 kg
Measurement System :
TRANDUCER SIGNAL CONDITIONING
DISPLAY/READOUT DEVICE/
CONTROL SYSTEM
POWER SUPPLY
INPUT MEASURAND
Tranducer
• Convert the measurand into a usable electrical output
=> “ A device capable of being actuated by an energizing input from one or more transmission media and in turn, generating a related signal to one or more transmission system or media “
=> Energy is one form of information
Signal Conditioning :
• Convert transducer output into electrical quantity suitable for display or next control system– Amplifiers– Signal Generation– Filtering– Converting
Display and Power Supply
• Display/readout/next control system– Analog Display– Digital Display
• Power Supply : provides the requires excitation
Tranducer Classification• Mechanical Tranducer
– Operate without any external power supply
– Posses high accuracy– Low cost– Requirement of large forces =>
mechanical friction– Incompability with other sensing
element– Not suitable for long distance
measurement• example : dial gauge, barometer
Dial Gauge
Barometer
Tranducer Classification (2)• Electrical Tranducer :
– Output can be amplified to any desired level – Output can be indicated and recordes remotely at
a distance– Output can be modified to meet requirement of
display, or controlling other device (sinyal -> tegangan atau arus, analog -> frekuensi atau pulsa)
– The signal can be conditioned or mixed to obtain any combination output
Disadvantates : less reliable => precision problem
Tranduser Elektrik• Suatu device yang dapat melakukan ‘sensing’
terhadap suatu besaran fisik, mekanik dan optikal yang diukur, dan mengubahnya menjadi nilai tegangan atau arus yang proporsional dengan masukan yang diukur
Klasifikasi Tranduser Elektrik :
• Tranduser Aktif
• Tranduser Pasif
Tranduser Aktif
• ‘self generating device’ , bekerja menurut hukum konversi energi
• Dapat membangkitkan sinyal output listrik yang ekivalen tanpa adanya sumber energi luar– Contoh : tekanan ke arus, temperatur ke
tegangan
Tranduser Aktif
PiezoelectricSolar Cell
Tranduser Pasif
• Bekerja berdasarkan prinsip pengontrolan energi
• Bergantung pada perubahan parameter listrik (resistansi, induktansi, kapasitansi)
• Diperlukan penggerak dari luar– Contoh : strain gauge ; digerakan sumber DC
Tranduser Pasif
Tabel 1 : Klasifikasi Tranduser Elektrik
Tabel 2 : Dimentional relationship between parameter
Basic Quantity Measured Parameter
Linear Displacement Length, width, tickness, position, level, surface quality, strain, velocity accelaration
Angular Displacement Altitude, angle of incidence, angle of flow, angle of vibration
Linear Velocity Speed, rate of flow, momentum, vibration
Angular velocity Angular speed, rate of turn, angular momentum, vibration
Linear acceleration Vibration, impact, motion
Angular acceleration Torque, angular vibration, angular impact, moment of inertia
Basic Quantity Measured Parameter
Force Weight, thrust, density, stress, torque, vibration, acceleration, pressure, flow, fluid velocity, sound intensity
Temperature Gas & Liquid expansion, heat flow, heat conductivity, fluid flow, surface temperature, radiation pressure, gas velocity, turbulence
Light Light Flux & density, temperature, length, force, torque, frequency
Time Frequency, number of events, statistical distributin
Electromagnetic radiation Wavelength, power, field strength
Dimentional relationship between parameter (2)
Keperluan dasar Tranduser
• Ruggedness (kokoh) : kemampuan pada overload
• Linearity : menghasilkan hubungan input – output yang linear
• Repeatibility : menghasilkan sinyal output yang tepat sama bila dilakukan pengukuran berulang
• S/N (signal to noise ) rasio yg cukup besar => SNR = Psignal / Pnoise
Keperluan dasar Tranduser (2)
• Stabilitas dan Keandalan (Stability and Reliability) : respon hasil pengukuran terhadap keadaan lingkungan
• Dynamic Response : perbandingan yang baik antara input dan output terhadap fungsi waktu
Contoh Spesifikasi : Pressure Tranduser
References :1. Rangan, C.S., "Instrumentation, Device and Systems",
Tata McGraw-Hill Publishing Company Limited, New Delhi, 1987.
2. Hall, Douglas V., "Microprocessor and Interfacing", McGraw-Hill Book Company, Singapore, 1986.
3. William D. Cooper “Instrumentasi Elektronika dan Teknik Pengukuran” Penerbit : Erlangga 1993
4. Wobschall, Darold., “ Circuit Design for Electronic Instrumentation”, McGraw-Hill, 1987
5. Internet