Sistem Instrumentasi

Sistem Instrumentasi

Sensor Gerakan (posisi dan kecepatan) Ir. Jos Pramudijanto, M.Eng. Jurusan Teknik Elektro FTI ITS Telp. 5947302 Fax.5931237 Email: [email protected] Instrumentasi Sistem Pengaturan - 06

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Pengantar Objektif: Macam sensor posisi dan sensor kecepatan Metode pengukuran dengan sensor posisi dan kecepatan

Definisi: Suatu sensor yang mengkonversikan perubahan gerakan suatu objek menjadi energi listrik Suatu perubahan kecepatan bisa didapatkan dari perubahan posisi

Instrumentasi Sistem Pengaturan - 06

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Sensor Posisi Resistive Potentiometers

Inductive Linear Variable Differential Transformers (LVDTs) Synchros, Resolvers, and Inductosyn

Electro-optical Optical encoders

Capacitive, piezo-electric, ultrasonic, magnetostrictive, etc.


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Potensiometer Sensor analog yang bekerja seperti divider


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Potensiometer dan Proximity Potensiometer (rotary and linear)

Proximity switch (mechanical)


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Potensiometer untuk posisi


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LVDT Linear-Variable Differential Transformer


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Konstruksi LVDT LVDT terdiri dari magnetic core yang bergerak dalam silinder.


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Prinsip Kerja LVDT Inti berada di tengah-tengah maka : Flux S1 = S2 Tegangan induksi E1 = E2 Enetto = 0

Inti bergerak ke arah S1 maka : Flux S1 > S2 tegangan induksi E1 > E2, Enetto = E1 - E2

Inti bergerak ke arah S2 maka : Flux S1 < S2 Tegangan induksi E1 < E2 Enetto = E2 – E1


Synchro


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Rangkaian Synchro


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Synchro to Digital Converter


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Resolver Uses an AC signal to excite the rotor winding. Stator has two windings at 90 degrees to each other. As the rotor turns the coupling to the two windings will change

Cosine Reference

Sin


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Rangkaian Resolver


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Inductosyn Similar to a resolver but made in two planes. The Inductosyn has many pole pairs, +50 The output will repeat ones for each pole pair. Each cycle can be decoded to +14 bits Require very precise alignment, and high quality amplifiers. Analog Encoders offer similar solution at a lower cost.


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Konstruksi Inductosyn


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Optical Encoder


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Sinyal Output Optical Encoder


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Increment Encoder Generally Have two picks up that are 90 degrees out of Phase (A and B) This allows you to determine the direction of rotation and thus count up or down By using the rising and falling edges of both A and B we can get 4 times the number of slots. May have one or more index marks for homing.


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Absolute Encoder Gray Code Vs Binary Gray Code only changes by one bit per transition. At least one sensor per track. 11

01

11

01

01

00

00

10


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Pengukuran dg Encoder Absolute ! Shaft Encoder convert position into binary equivalent.

This system use 8 bit shaft encoder. So, the resolution of shaft encoder is :

360 o resolution = 8 = 1, 41 2 ! The linear displacement is :

angle linear displaceme nt = Χ 2π r o 360 Instrumentasi Sistem Pengaturan - 06

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Konstruksi Encoder Increment


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Konstruksi Encoder Increment


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Konstruksi Encoder Absolut


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Perbandingan Sensor Posisi Incremental Encoder dan Resolver paling populer

Type Encoder Incremental Encoder Absolute Sinusoidal Encoders Resolver Inductosyn Capacitive Inductive

Resolution Bits

Incremental or Absolute

Signal Type

12

Incremental

Digital

16

Absolute

Digital

Binary

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Absolute

Analog

Sin, Cos, Index

Fair

6-10

Interpolator

14

Absolute

Sin,Cos

Good

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R/D Converter

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Incremental

Sin, Cos

Fair

6

Amp +Converter

24

Either

Sin, Cos

Fair

6-10

Converter

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Either

Sin, Cos

Fair

6-10

Converter

Analog Volts RMS Analog millivolts Analog millivolts Analog millivolts

Signals A, B, Index

Electrical Number Imunity of Wires Very 4-8 Good Very 20+ Good


Electrical Interface None None

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Sensor Kecepatan Inductive tachogenerators linear sensors

Gyroscopes Differentiation of position analog digital

Integration of acceleration Instrumentasi Sistem Pengaturan - 06

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Tachogenerator Sensor ini konstruksinya mirip motor DC magnet permanen. Tegangan keluaran yang dihasilkan berupa tegangan DC.


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Increment Encoder Encoder yang digunakan untuk pengukuran kecepatan menggunakan encoder dengan output A, B, dan Z Output A dan B berbeda phase sebesar 90 derajat. Sedang output Z untuk zero index (untuk kecepatan tinggi).


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Accelerometer Accelerometer bahan piezo-electric. Pengukuran kecepatan dengan membuat rangkaian integrator.


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Capacitive and Inductive Sensors Operate similar to analog encoders. Patterns are placed on the rotor and stator. Rotor and stator can be made of low cost materials Technology similar to printed circuit board fabrication. Capable of very low power operation. This would allow for battery baked operation. Resolution similar to analog encoders and Inductosyns Electronics utilize Digital to Analog converters and DSPs or PLDs.


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Sistem Instrumentasi

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