4 SCHEDULE OF ASSESSMENT Method of assessmentPercentage of total1Attendance04 %2Quizzes and Homework and Reports8 %4Two Mid Term Exams2×10 %=20 %5Final Exam40 %Total(Note: 2% Bonus are given to students who attend more than 95% of classes)72 %
5 Contents MEASUREMENT FUNDAMENTALS Definition of measurement and instrumentationTypes of measurementsTypes of instruments in measurementsReview in units of measurementStandard of measurementCalibrationApplication of measurement and instrumentation
6 Definition Measurement Instrumentation A method to obtain information regarding the physical values of the variable.the process of determining the amount, degree or capacity by comparison with the accepted standards of the system units being usedInstrumentationDevices used in measurement systemdevice for determining the value or magnitude of a quantity or variable
7 FUNCTION AND ADVANTAGES The 3 basic functions of instrumentation :-Indicating – visualize the process/operationRecording – observe and save the measurement readingControlling – to control measurement and processAdvantages of electronic measurementResults high sensitivity rating – the use of amplifierIncrease the input impedance – thus lower loading effectsAbility to monitor remote signal
8 Purpose of a measurement system MeasurandSensor, signal conditioning, displayMan, tracking control etcA measuring system exists to provide information about the physical value ofsome variable being measured.
9 Examples of Electronic Sensor applications Uses infrared optical sensorNew Solar Power Faucet by Sloan Valve0.5 gpm aerator regulates water flowElectronic sensor automatically turns water on/offIntegral temperature control
10 PERFORMANCE CHARACTERISTICS Performance Characteristics - characteristics that show the performance of an instrument.Eg: accuracy, precision, resolution, sensitivity.Allows users to select the most suitable instrument for a specific measuring jobs.Two basic characteristics :Static – measuring a constant process condition.Dynamic - measuring a varying process condition.
11 PERFORMANCE CHARACTERISTICS Accuracy – the degree of exactness (closeness) of measurement compared to the expected (desired) value.Resolution – the smallest change in a measurement variable to which an instrument will respond.Precision – a measure of consistency or repeatability of measurement, i.e successive reading do not differ.Sensitivity – ratio of change in the output (response) of instrument to a change of input or measured variable.Expected value – the design value or the most probable value that expect to obtain.Error – the deviation of the true value from the desired value.
12 TerminologiesPhysical quantity: variable such as pressure, temperature, mass, length, etc.Data: Information obtained from the instrumentation/measurement system as a result of the measurements made of the physical quantitiesInformation: Data that has a calibrated numeric relationship to the physical quantity.Parameter: Physical quantity within defined (numeric) limits.
13 Terminology Measurand: Physical quantity being measured. Calibration: Implies that there is a numeric relationship throughout the whole instrumentation system and that it is directly related to an approved national or international standard.Test instrumentation: It is a branch of instrumentation and most closely associated with the task of gathering data during various development phases encountered in engineering, e.g. flight test instrumentation for testing and approving aircraft.
14 TerminologiesTransducer: A device that converts one form of energy to another.Electronic transducer: It has an input or output that is electrical in nature (e.g., voltage, current or resistance).Sensor: Electronic transducer that converts physical quantity into an electrical signal.Actuator: Electronic transducer that converts electrical energy into mechanical energy.
15 Why measurement?In the case of process industries and industrial manufacturing…To improve the quality of the productTo improve the efficiency of productionTo maintain the proper operation.
16 Why instrumentation?To acquire data or information (hence data acquisition) about parameters, in terms of:putting the numerical values to the physical quantitiesmaking measurements otherwise inaccessible.producing data agreeable to analysis (mostly in electrical form)Data Acquisition Software (DAS) – data is acquired by the instrumentation system.
17 Types of measurements Direct comparison Indirect comparison Easy to do but… less accuratee.g. to measure a steel barIndirect comparisonCalibrated system; consists of several devices to convert, process (amplification or filtering) and display the outpute.g. to measure force from strain gages located in a structure
18 Generalised measuring system General Structure of Measuring SystemStage 1: A detection-transducer or sensor-transducer, stage; e.g. Bourdon tubeStage 2: A signal conditioning stage; e.g. gearing, filters, bridgesStage 3: A terminating or readout-recording stage; e.g. printers, oscilloscope
20 Types of instruments in measurements Active Instrumentsthe quantity being measured simply modulates (adapts to) the magnitude of some external power source.Passive Instrumentsthe instrument output is entirely produced by the quantity being measuredDifference between active & passive instruments is the level of measurement resolution that can be obtained.
21 Active Instruments e.g. Float-type petrol tank level indicator Circuit excitedby externalpower source(battery)
22 Petrol tank level indicator The change in petrol level moves a potentiometer arm, and the output signal consists of a proportion of the external voltage source applied across the two ends of the potentiometer.The energy in the output signal comes from the external power source: the primary transducer float system is merely modulating the value of the voltage from this external power source.
24 Passive pressure gauge The pressure of the fluid is translated into a movement of a pointer against scale.The energy expanded in moving the pointer is derived entirely from the change in pressure measured: there are no other energy inputs to the system.
25 Analogue InstrumentsAn analogue instrument gives an output that varies continuously as the quantity being measured; e.g. Deflection-type of pressure gauge
26 Digital InstrumentsA digital instrument has an output that varies in discrete steps and only have a finite number of values; e.g. Revolution counter
27 Units Of MeasurementTo define physical quantities in type and magnitudeUnits of measurement may be defined as the standard measure of each kind of physical quantity.Efforts were made to standardise systems of measurement so that instrument professionals and specialist in other disciplines could communicate among themselves.
29 Fundamental Units & Derived Units Two types of units are used in science and engineeringFundamental units ( or quantities)E.g. meter (length), kilogram (mass), second (time)Derived units (or quantities); i.e. All units which can be expressed in terms of fundamental unitsE.g. The volume of a substance is proportional to its length (l), breadth (b) and height (h), or V= l x b x h.So, the derived unit of volume (V) is cube of meter (m3).
32 Systems Of Units Centimeter-gram-second(C.G.S) Foot-pound-second (F.P.S.)MetricSI
33 Standard Of Measurement As a physical representation of a unit of measurementA standard is a known accurate measure of physical quantity.Standards are used to determine the values of other physical quantities by the comparison method.All standards are preserved at the International Bureau of Weight and Measures (BIMP), Paris.Four categories of standard:International StandardPrimary StandardSecondary StandardWorking StandardIt is used for obtaining the values of the physical properties of other equipment by comparison methods; e.g.The fundamental unit of mass in the SI system is the kilogram, defined as the mass of a cubic decimeter of water at its temperature of maximum density of 4C.
34 Standard International Std Defined by International Agreement Represent the closest possible accuracy attainable by the current science and technologyPrimary StdMaintained at the National Std Lab (different for every country)Function: the calibration and verification of secondary stdEach lab has its own secondary std which are periodically checked and certified by the National Std Lab.For example, in Malaysia, this function is carried out by SIRIM.
35 Standard Secondary Standard Secondary standards are basic reference standards used by measurement and calibration laboratories in industries.Each industry has its own secondary standard.Each laboratory periodically sends its secondary standard to the National standards laboratory for calibration and comparison against the primary standard.After comparison and calibration, the National Standards Laboratory returns the secondary standards to particular industrial laboratory with a certification of measuring accuracy in terms of a primary standard.Working StdUsed to check and calibrate lab instrument for accuracy and performance.For example, manufacturers of electronic components such as capacitors, resistors and many more use a standard called a working standard for checking the component values being manufactured.
36 Examples of Standard Bodies International Organization for Standardization (ISO)International Electrotechnical Commission (IEC)American National Standards Institute (ANSI)Standards Council of Canada ( SCC)British Standards (BS)
37 Calibration Calibration consists of comparing the output of the instrument or sensor under test against the output ofan instrument of known accuracy (higher accuracy)when the same input (the measured quantity is appliedto both instrument)The procedure is carried out for a range of inputs coveringthe whole measurement range of the instrument or sensorEnsures that the measuring accuracy of all instruments andsensors used in a measurement system is known over thewhole measurement range, provided that the calibratedinstruments and sensors are used in environmental conditionsthat are the same as those under which they were calibrated
38 Calibration involve a comparison of an instrument with either: A primary standardA secondary standardA known inputStandard weightmeasurement facility(for example: NIST)Example:Weighing instrumentAnother weighinginstrument of higheraccuracyMass standard
39 CalibrationThe method and apparatus for performing measurement instrumentation calibrations vary widely.A rule that should be followed is that the calibration standard should be at least 10 times as accurate as the instrument being calibrated.By holding some inputs constant, varying others and recording the output(s) develop the desired static input-output relations. Many trial and runs are needed.
40 Application Home Road vehicles Industry Thermometer Barometer Watch speedometerfuel gaugeIndustryAutomationProcess controlBoiler control