Instrumentasi Sistem Pengaturan - 06 1
Sistem Instrumentasi
Sensor Gerakan (posisi dan kecepatan)
Ir. Jos Pramudijanto, M.Eng.Jurusan Teknik Elektro FTI ITS
Telp. 5947302 Fax.5931237Email: [email protected]
Instrumentasi Sistem Pengaturan - 06 2
PengantarObjektif:
Macam sensor posisi dan sensor kecepatanMetode pengukuran dengan sensor posisi dan kecepatan
Definisi:Suatu sensor yang mengkonversikan perubahan gerakan suatu objek menjadi energi listrikSuatu perubahan kecepatan bisa didapatkan dari perubahan posisi
Instrumentasi Sistem Pengaturan - 06 3
Sensor PosisiResistive
Potentiometers
InductiveLinear Variable Differential Transformers (LVDTs)Synchros, Resolvers, and Inductosyn
Electro-opticalOptical encoders
Capacitive, piezo-electric, ultrasonic, magnetostrictive, etc.
Instrumentasi Sistem Pengaturan - 06 5
Potensiometer dan Proximity
Potensiometer (rotary and linear)
Proximity switch (mechanical)
Instrumentasi Sistem Pengaturan - 06 8
Konstruksi LVDT
LVDT terdiri dari magnetic core yang bergerak dalam silinder.
Instrumentasi Sistem Pengaturan - 06
Prinsip Kerja LVDT
Inti berada di tengah-tengah maka :Flux S1 = S2Tegangan induksi E1 = E2Enetto = 0
Inti bergerak ke arah S1 maka :Flux S1 > S2tegangan induksi E1 > E2, Enetto = E1 - E2
Inti bergerak ke arah S2 maka :Flux S1 < S2Tegangan induksi E1 < E2Enetto = E2 – E1
Instrumentasi Sistem Pengaturan - 06 13
Resolver
Sin
Cosine
Reference
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
Instrumentasi Sistem Pengaturan - 06 15
Inductosyn
Similar to a resolver but made in two planes.The Inductosyn has many pole pairs, +50The output will repeat ones for each pole pair.Each cycle can be decoded to +14 bitsRequire very precise alignment, and high quality amplifiers.Analog Encoders offer similar solution at a lower cost.
Instrumentasi Sistem Pengaturan - 06 19
Increment EncoderGenerally 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 downBy 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.
Instrumentasi Sistem Pengaturan - 06 20
Absolute Encoder
Gray Code Vs BinaryGray Code only changes by one bit per transition.At least one sensor per track.
0111
01 00
0111
00 10
Instrumentasi Sistem Pengaturan - 06 21
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 :
!The linear displacement is :
oresolution 41,12
3608 ==
ranglentdisplacemelinear o π2360
Χ=
Instrumentasi Sistem Pengaturan - 06 25
Perbandingan Sensor Posisi
TypeResolution
BitsIncremental or Absolute
Signal Type Signals
Electrical Imunity
Number of Wires
Electrical Interface
Encoder Incremental
12 Incremental Digital A, B, Index
Very Good
4-8 None
Encoder Absolute
16 Absolute Digital Binary Very Good
20+ None
Sinusoidal Encoders
22 Absolute Analog Sin, Cos, Index
Fair 6-10 Interpolator
Resolver14 Absolute Analog
Volts RMSSin,Cos Good 6 R/D Converter
Inductosyn24 Incremental Analog
millivoltsSin, Cos Fair 6 Amp +Converter
Capacitive24 Either
Analog millivolts Sin, Cos Fair 6-10 Converter
Inductive 24 Either Analog millivolts
Sin, Cos Fair 6-10 Converter
Incremental Encoder dan Resolver paling populer
Instrumentasi Sistem Pengaturan - 06 26
Sensor KecepatanInductive
tachogeneratorslinear sensors
GyroscopesDifferentiation of position
analogdigital
Integration of acceleration
Instrumentasi Sistem Pengaturan - 06 27
Tachogenerator
Sensor ini konstruksinya mirip motor DC magnet permanen.Tegangan keluaran yang dihasilkan berupa tegangan DC.
Instrumentasi Sistem Pengaturan - 06 28
Increment EncoderEncoder yang digunakan untuk pengukuran kecepatan menggunakan encoder dengan output A, B, dan ZOutput A dan B berbeda phase sebesar 90 derajat. Sedang output Z untuk zero index (untuk kecepatan tinggi).
Instrumentasi Sistem Pengaturan - 06 29
Accelerometer
Accelerometer bahan piezo-electric.Pengukuran kecepatan dengan membuat rangkaian integrator.
Instrumentasi Sistem Pengaturan - 06 30
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 materialsTechnology 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 InductosynsElectronics utilize Digital to Analog converters and DSPs or PLDs.