LECTURE 1 PRINCIPLES OF INSTRUMENTATION AND MEASUREMENT.pptx

LECTURE 1 PRINCIPLES OF INSTRUMENTATION AND MEASUREMENT.pptx

1. PRINCIPLES OF INSTRUMENTATION AND MEASUREMENT MOHD ZAMZURI AB RASHID FACULTY OF TECHNOLOGY AND ELECTRICAL ENGINEERING, UNIVERSITI TEKNIKAL MALAYSIA MELAKA

2. LECTURER INFO

3. Outcome of the Learning At the end of this chapter, student should be able to: 1.Define various measurement and instrument principles, application, terms and standards. 2.Define and explain the following types of errors that occur in measurements: gross, systematic, random. 3.Use basic statistical methods for analyzing measurement errors, accuracy, precision and limiting error. 4.Describe types of noise occur in measurement, effects and reduction techniques.

4. Chapter Outline 1. Introduction 2. SI Units & Dimension 3. Standards of Measurements 4. Standards of Electrical Measurements

5. Introduction: Instrument Definition of Instrumentation Term: Instrument is a device or mechanism used to determine the value or magnitude of a quantity under observation. Electronic instrument is a device that based on electrical or electronic principles to do measurement. Instrumentation system is a physical system , which is collection of physical objects connected in such a way to give the desired output response . Other definition = assembly of various instruments and other components interconnected to measure, analyze and control the electrical, thermal, hydraulic and other non-electrical physical quantities.

6. Basic functions instruments:

7. Indicating - oscilloscope

8. Recording – strip chart recorder

9. Controlling - automatic control system

10. Introduction: Measurement Measurement is the process of determining the amount, degree or capacity by comparing with the accepted standards of the system units being used. Standard is the physical form of the unit of measurement as well as that of its submultiple or multiple value Measuring Instrument is the device used for comparing the unknown quantity with the unit of measurement or a standard quantity

11. Introduction: Measurement

12. Introduction: Measurement Method 1: Indirect measurement methods The unknown quantity is determined by measuring other functionally related quantities and calculating the desired quantity rather than measuring it directly with an instrument. Use formula to get the desired quantity. Example resistance, R = Voltage / current. resistance of a conductor may be determined by measuring voltage across the conductor, V and current flowing through the conductor, I and calculating by Ohm’s law

13. Introduction: Measurement M ethod 2: Direct measurement methods The unknown quantity is directly compared against a standard . The result is expressed as a numerical number and a unit . Direct methods are quite common for the measurement of physical quantities like length, mass and time. Generally direct measurement can be classified into two types : i . Deflection method ii. Comparison method

14. Introduction: Measurement M ethod 2: Direct measurement methods 1. Deflection ( pesongan ) methods The value of unknown quantity is determined by means of measuring instrument having a scale graduated to the quantity under measurement directly or simply the desired measured quantity is measured by using the measuring instrument that have the same quantity E.g. measurement of current with an ammeter.

15. Introduction: Measurement M ethod 2: Direct measurement methods 2. Comparison methods The unknown quantity is determined by direct comparison with a standard of the given quantity It is applicable to quantities that can be reproduced by standards. This method usually affords greater precision than indirect measurement because the error of the result is chiefly determined by the insignificant error of the standard, and the residual errors can be kept to low values.

16. Introduction: Measurement Comparison methods Comparison methods = divided into several method opposition method difference method null method substitution method coincidence method.

17. Introduction: Measurement Comparison methods Comparison methods = divided into several method Opposition method measure two quantities & the quantity reproduced measured simultaneously on the comparison device. consider standard act. example as in measuring a weight on a balance Difference method difference between quantities acts on a comparison device . for example, in comparing the lengths gage blocks on an interferometer

18. Introduction: Measurement Comparison methods Comparison methods = divided into several method Null method resultant effect of the comparison is zero for example, in measuring resistance by means of a DC bridge with complete balancing.

19. Introduction: Measurement Null method Measuring current and voltage more accurately by balancing the circuit so that no current flows through the measurement device (using potentiometer/ variable resistor and Wheatstone bridge). Voltmeters draw some extra current, whereas ammeters reduce current flow. Null measurements balance voltages, so there is no current flowing through the measuring device and the circuit is unaltered. Null measurements = more accurate but more complex than standard voltmeters and ammeters. The precision is still limited

20. Example null method TO MEASURE EMF OF A BATTERY. connect the battery directly to a standard voltmeter. actual quantity measured = terminal voltage V, which is related to the emf of the battery by V =emf− Ir I is the current that flows r is the internal resistance of the battery. emf could be accurately calculated if r were very accurately known, but it is usually not.