Post on 06-Apr-2018
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
1/47
Pengenalan kepada Sistem
Instrumentasi dan Pengukuran
EMM 3242
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
2/47
Rangka Kursus
Ujian 30% -Ujian 1 (15%) & Ujian 2 (15%) Kuiz /Assignment/Tugasan (20%)
Peperiksaan Akhir-50%
Passing Marks = 40%
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
3/47
Sillibus
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
4/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
5/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
6/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
7/47
BUKU RUJUKAN
Anthony J.Wheeler & Ahmad R Ghanji, Introduction to EngineeringExperimentation, 3 rd edition,2009.
J.P. Holman, Experimental Methods for Engineers,7 th edition,
McGraw Hill, 2001 D.G. Alciatore & M.B Histand, Introduction to Mechatronics and
Measurements Systems, 2 nd edition . Mc Graw hill 2003 C.D Johnson, Process Control Instrumentation Technology, Pearson A.S Morris, Principle of Measurements and Instrumentation, 2 nd
edition, Prentice Hall, 1993
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
8/47
Contoh Sistem Pengukuran
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
9/47
Definasi
Pengukuran -suatu langkah yang diambil untuk
melakukan proses perbandingan antaranilar sebenar dengan nilai yang diuji.
Sistem Pengukuran- Untuk mengukur sesuatu pemboleh ubah
atau measurans dan menukarkankepada suatu bentuk yang mudahdifahami oleh pengukur
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
10/47
Sistem Unit
Diperlukan untuk memperterjemahsesuatu nilai yang diukur.
Contoh:a) Sistem Unit Antarabangsa (International
System-SI)
b) Sistem Unit CGS (Centimeter-Gram-Second)c) Sistem English (Imperial)
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
11/47
7 unit asas SI
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
12/47
Unit Asas CGS
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
13/47
Perbandingan antara Unit
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
14/47
EX 1
Ex: Convert the length 56.43ft to itsequivalent units of metres..
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
15/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
16/47
EX 2
According to one internet site the distancefrom Vancouver B.C to Hong Kong is 5550nautical miles as the crow flies. Determinewhat this distance in units of kilometers..
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
17/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
18/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
19/47
Definasi Instrumentasi
Sistem peranti (device,equipment) yangdigunakan dalam pengukuran
Kompenen utama :transducer,penyesuaian isyarat & unitpaparan
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
20/47
WHY NEED MEASUREMENT?
1.? 2.?
3.?
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
21/47
Why Need Measurement?
1. Monitoring or logging of processes andoperations
2. Experimental analysis of processes3. Control of processes
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
22/47
1> the measurements simply provide a record whichmay be used as required. Example .. Whether data,aircraft black box recorders
2> the measurements are being taken for specificpurposes.. Example.. To determine the performance of anew engine, or to verify the accuracy of a mathematicalsimulation model
3> measurements are used as part of an automaticfeedback control system.. Example .. Include thethermostat in a central heating system or car engine,robot arm position measurement
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
23/47
Hubungan antara masukan dan keluaran bongkah atauoutput.
Terdiri daripada 2 bahagian : statik & dinamik
Statik -menghubungkan masukan (input) dan keluaran (output
apabila masukan (input) tidak berubah dengan masa.-diwakili oleh persamaan, jadual atau graf
Dinamik -diwakili oleh persamaan kebezaan. (bab akan datang)
Rangkap Pindah (Transfer Characteristics)
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
24/47
Ralat (error)
e , Perbezaan diantara nilai sebenar X n dan nilai yang diukur Y n e = Y
n - X
n Boleh diklasifikasi kepada 2 jenis:a) Ralat Sistematik (Systematic Error)
b) Ralat Rawak/Rambang (Random Error)
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
25/47
Ralat Sistematik-ralat yang berlaku berulangkali dengan nilai
yang tetap.Punca:i) tidak mengunakan alat dengan teknik yang betul
ii) Ketentu ukuran yang silapiii) Kesilapan manusia apabila membacaiv) Kesilapan rekabentuk atau fakbrikasi alatv) Pengukuran yang berubah-ubah
Peratus Ralat= Yn - Xn x 100 e x 100Yn Yn
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
26/47
Ralat Rawak-ralat yang tidak konsisten dalam sistem
pengukuran.Punca:i) Pemerhati yang tidak dapat menganggarkan dengan
tepat semasa mengambil bacaanii) Kebisingan atau gangguan dari persekitaran atau
sistem lain mempengaruhi pemboleh ubah yangdiukur
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
27/47
Analog and digital data Variables are analog in nature, and before digital processing evolved, sensor signals were processed using analog circuits and techniques, which still exist in many processing facilities. Most modern systems now use digital techniques for signal processing [5]. Analog Data
Signal amplitudes are represented by voltage or current amplitudes in analogsystems.
Analog processing means that the data, such as signal linearization, from the sensor is conditioned, and corrections that are made for temperature variations are all performed using analog circuits. Analog processing also controls the actuatorsand feedback loops. The most common current transmission range is 4 to 20 mA, where 0 mA is a fault
indication.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
28/47
Example The pressure in a system has a range from 0 to 75 kPa. What is the
current equivalent of 27 kPa, if the transducer output range is from 4to 20 mA?
Equivalent range of 75 kPa = 16 mAHence, 27 kPa = (4 + 16 27/75) mA = 9.76 mA
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
29/47
Digital Data
Digital Data Signal amplitudes are represented by binary numbers in digital systems.
Since variables are analog in nature, and the output from the sensor needsto be in a digital format, an analog to digital converter (ADC) must be used,or the sensor s output must be directly converted into a digital signal usingswitching techniques.
Once digitized, the signal will be processed using digital techniques, whichhave many advantages over analog techniques, and few, if any,disadvantages.
Some of the advantages of digital signals are: data storage, transmission of
signals without loss of integrity, reduced power requirements, storage of setpoints, control of multiple variables, and the flexibility and ease of programchanges.
The output of a digital system may have to be converted back into ananalog format for actuator control, using either a digital to analog converter(DAC) or width modulation techniques.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
30/47
FIGURE 1.11 Graph (a) shows how output variable b changes as an analog of variable c . Graph (b) shows how a digitaloutput variable, n , would change with variable c .
Curtis JohnsonProcess Control Instrumentation Technology, 8e]
Copyright 2006 by Pearson Education, Inc.Upper Saddle River, New Jersey 07458
All rights reserved.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
31/47
Introduction to process control The technology of controlling a series of events to transform a material into
a desired end product is called process control. For instance, the making of fire could be considered a primitive form of
process control. Industrial process control was originally performedmanually by operators.
Their sensors were their sense of sight, feel, and sound, making theprocess totally operator-dependent.
To maintain a process within broadly set limits, the operator would adjust asimple control device.
Instrumentation and control slowly evolved over the years, as industry found
a need for better, more accurate, and more consistent measurements fortighter process control.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
32/47
Process Control
Process control can take two forms:(1) sequential control,
which is an event-based process in which oneevent follows another until a process sequenceis complete; or
(2) continuous control,
which requires continuous monitoring andadjustment of the process variables.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
33/47
Sequential Process control Control systems can be sequential in nature, or can use continuous
measurement; both systems normally use a form of feedback for control. Sequential control
is an event-based process, in which the completion of one event follows the
completion of another, until a process is complete, as by the sensing devices. Figure 1.1
shows an example of a process using a sequencer for mixing liquids in a set ratio [2].
The
sequence of events is as follows:
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
34/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
35/47
1. Open valve A to fill tank A. 2. When tank A is full, a feedback signal from the level sensor tells the sequencer to turn valve A Off. 3. Open valve B to fill tank B. 4. When tank B is full, a feedback signal from the level sensor tells the sequencer to turn valve B Off.
5. When valves A and B are closed, valves C and D are opened to let measured quantities of liquids A and B into mixing tank C. 6. When tanks A and B are empty, valves C and D are turned Off. 7. After C and D are closed, start mixing motor, run for set period. 8. Turn Off mixing motor. 9. Open valve F to use mixture.
10. The sequence can then be repeated after tank C is empty and Valve F is turned Off.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
36/47
Continuous Process Control
Continuous process control falls into two categories: (1) elementary On/Off action, and (2) continuous control action. On/Off action is used in applications where the system has high inertia,
which prevents the system from rapid cycling. This type of control only hasonly two states, On and Off; hence, its name. This type of control has been
in use for many decades, long before the introduction of the computer.
HVAC is a prime example of this type of application. Such applications donot require accurate instrumentation.
In HVAC, the temperature (measured variable) is continuously monitored,
typically using a bimetallic strip in older systems and semiconductorelements in newer systems, as the sensor turns the power (manipulatedvariable) On and Off at preset temperature levels to the heating/coolingsection.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
37/47
EX 1..automated controlprocess
An example of an unsophisticated automated control process is shown inFigure 1.2.
A float in a swimming pool is used to continuously monitor the level of thewater, and to bring the water level up to a set reference point when thewater level is low.
The float senses the level, and feedback to the control valve is via the floatarm and pivot. The valve then controls the flow of water (manipulatedvariable) into the swimming pool, as the float moves up and down.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
38/47
Ex 2. continuous control forliquid mixing
A more complex continuous process control system is shown inFigure 1.3,
where a mixture of two liquids is required. The flow rate of liquid A is measured with a differential pressure
(DP) sensor, and the amplitude of the signal from the DP measuringthe flow rate of the liquid is used by the controller as a referencesignal (set point) to control the flow rate of liquid B.
The controller uses a DP to measure the flow rate of liquid B, andcompares its amplitude to the signal from the DP monitoring the flowof liquid A. The difference between the two signals (error signal) isused to control the valve, so that the flow rate of liquid B(manipulated variable) is directly proportional to that of liquid A, andthen the two liquids are combined
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
39/47
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
40/47
Measurement VS
Sensors VSInstruments ?
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
41/47
Measurement is the determination of the physical amplitude of aparameter of a material; the measurement value must be consistentand repeatable.
Sensors are typically used for the measurement of physicalparameters. A sensor is a device that can convert the physicalparameter repeatedly and reliably into a form that can be used orunderstood.
Examples include converting temperature, pressure, force, or flowinto an electrical signal, measurable motion, or a gauge reading. InFigure 1.3, the sensor for measuring flow rates is a DP cell.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
42/47
The subtle difference between an instrumentand a sensor is that an instrument is a devicethat measures and displays the magnitude of a
physical variable, whereas a sensor is a device that measures the
amplitude of a physical variable, but does notgive a direct indication of the value
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
43/47
Definition of elements in acontrol loop
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
44/47
Controller is a microprocessor-based system that candetermine the next step to
be taken in a sequential process, or evaluate the errorsignal in continuous process
control to determine what action is to be taken. Thecontrollers are normally referred to as
programmable logic controllers (PLC). These devicesuse ladder networks for programming
the control functions.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
45/47
Control Element is the device that controls theincoming material to the process
(e.g., the valve in Figure 1.3).
The element is typically a flow control element,and can have an On/Off characteristic or canprovide liner control with drive.
The control element is used to adjust the input tothe process, bringing the output variable to thevalue of the set point.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
46/47
The measuring element consists of a sensor to measure thephysical property of a variable, a transducer to convert the sensorsignal into an electrical signal, and a transmitter to amplify theelectrical signal, so that it can be transmitted without loss.
The control element has an actuator, which changes the electricalsignal from the controller into a signal to operate the valve, and acontrol valve.
8/2/2019 Pen Gen Alan Kepada Sistem Instrumentasi Latest (Sem 2 2011.2012)
47/47