Instrumentation and Measurements Lecture Notes PDF

Instrumentation and Measurements Presented by Dr. Zeinab Elkady 2/14/2024 1 Lec.1 contents Basics of measurement systems ✓ What is Measurement, measurand and measuring instrument...

Instrumentation and Measurements Presented by Dr. Zeinab Elkady 2/14/2024 1 Lec.1 contents Basics of measurement systems ✓ What is Measurement, measurand and measuring instruments ? ✓ Standard of measurements ✓ Measuring Instruments ✓ The Importance of Measurement in Manufacturing ✓ Instruments from an idea to be a device ✓ Classification of measuring instruments Relative to: 1-methods of measurement 2-Relative to output signal 3-Relative to power source ✓ What are sensors, transducer, and actuators? ✓ transducer's principle of operations ✓ Transducer Static Characteristics /Selection Criteria  What is Measurement, measurand and measuring instruments ? Measurement: is a process of gathering information from a physical world and comparing this information with agreed standards Measurand: Physical parameter or variable to be measured (The output of the sensor unit) Measuring Instruments : are man-made devices for determining the value of the quantity/variable. ✓ It is a technique in which properties of an object are determined by comparing them to a standard. ✓ Accepted or approved instance or example of a quantity or quality against which others are judged or measured or compared ✓ As a physical representation of a unit of measurement ✓ It is used to obtain the values of the physical properties of other equipment by comparison methods Examples of standard bodies ✓ International organization for standardization (ISO) ✓ International Electromechanical Commission (IEC) ✓ American National Standards Institute (ANSI) ✓ Standard Council of Canada (SCC) ✓ British Standards (BS)  Measuring Instruments Instruments are man-made devices for determining the value of the quantity/variable. They are designed to maintain prescribed relationships between the parameters being measured and the physical variables under investigation Simple instrument model. A measuring system exists to provide information about the physical value of some variable being measured. In simple cases, the system can consist of only a single unit that gives an output reading or signal according to the magnitude of the unknown variable applied to it  SI Unit scientists use a system of measurement still commonly referred to as the “metric system.” The metric system was developed in France in the 1790s and was the first standardized system of measurement. Before that time, people used a variety of measurement systems. In 1960, the metric system was revised, simplified, and renamed the System International d’Unites (International System of Units) or SI system (meters, kilograms, etc.). This system is the standard form of measurement in almost every country around the world, except for the United States, which uses the U.S. customary units system (inches, quarts, etc.). The SI system is, however, the standard system used by scientists worldwide, including those in the United States The Importance of Measurement in Manufacturing correct dimensional measurement is a key factor in manufacturing Performing measurements with the same reference throughout all processes—from material reception to processing, assembly, inspection, and shipping—makes it possible to create products that match the design exactly and to guarantee product quality. The basic principle for correct measurements is to ensure that all those involved in manufacturing are skilled in measuring and that the measuring instruments are correctly managed and used. To improve the quality of the product To improve the efficiency of production To maintain the proper operation Instruments from an idea to be a device 1. Design of Instruments 2. Testing and Use of Instruments 3. Response and Drift 4. Accuracy and Errors 5- Error Reduction 6. Calibration of Instruments  1. Design of Instruments 2. Testing and Use of Instruments Instruments are designed on the After the instrument is designed and basis of existing knowledge, prototyped, various evaluation tests which is gained either from the may be conducted experiences of people about the some simulated environment tests physical processes or from the include climatic test, drop test, dust structured understanding of the test, insulation-resistance test, process. vibration test, electromagnetic compatibility tests, and safety and health hazard tests. Many of these are strictly regulated by national and international standards.  3. Response and Drift 4. Accuracy and Errors The response of the instruments The performance of an instrument to the signals can be analyzed in depends on its static and dynamic a number of ways by establishing characteristics. The performance may be static and dynamic performance indicated by its accuracy, which may be characteristics. described as the closeness of measured values to the real values of the variable. The total response is a combination of dynamic and static responses. The ideal or perfect instrument would have perfect sensitivity, reliability, and repeatability without any spread of values and would be within the applicable standards.  5- Error Reduction Controlling errors is an essential part of measurements and instrumentation. Various techniques are available to achieve this objective. The error control begins in the design stages by choosing the appropriate components, filtering, and bandwidth selection; by reducing the noise; and by eliminating the errors generated by the individual subunits of the complete system 6. Calibration of Instruments The calibration of all instruments is essential for checking their performances against known standards. This provides consistency in readings and reduces errors, thus validating the measurements universally. After an instrument is calibrated, the future operation is deemed to be error bound for a given period of time for similar operational conditions. The calibration procedure involves the comparison of the instrument against primary or secondary standards. In some cases, it may be sufficient to calibrate a device against another one with known accuracy.  Methods of measurement 1-Direct methods In direct measurement methods, the unknown quantity is measured directly instead of comparing it with a standard For example, measurement of current by an ammeter, voltage by voltmeter, Resistance by an ohmmeter, Power wattmeter Indicated by the deflection of the meter 2-In direct method The unknown quantity is determined by measuring the functionally related quantity and then calculating the desired quantity rather than measuring it directly For example, if we measure the voltage & the current across the resistance to calculate the resistance 14 February 2024 13 Classification of Measuring Instruments Relative to methods of measurement (primary and secondary sensors ) Absolute Instrument (indirect /primary instruments ) The absolute instrument gives the value of measures quantities regarding the physical constant. The physical constant means the angle of deflection, degree and meter constant. The mathematical calculation requires for knowing the value of a physical constant. E.g. the tangent galvanometer In terms of tangent of the angle of deflection produced, horizontal component of earths magnetic filed radius, no of turns of wire I = k * tan(θ) tangent galvanometer Secondary Instruments (direct instruments) In the secondary instrument, the deflection shows the magnitude of the measurable quantities. The calibration of the instruments with the standard instrument is essential for the measurement. The output of this type of device is directly obtained, and no mathematical calculation requires for knowing their value. E.g. the Ammeter directly indicate the value of the current The secondary instruments classified into indication integrating , integrating and recording instruments Indicating Instrument – The instrument which indicates the magnitude of the measured quantity is known as the indicating instrument. The indicating instrument has a dial that moves on the graduated dial. The voltmeter, Ammeter, pressure gauge are examples of the indicating instrument. Integrating Instrument – The instrument which measures the total energy supplied at a particular interval of time is known as the integrating instrument. The total energy measured by the instrument is the product of the time and measures electrical quantities. E.g. The energy meter, watt-hour meter and the energy meter are examples Recording Instrument – The instrument that records the circuit condition at a particular interval of time is known as the recording instrument. Gives a continuous record of variations of an electrical quantity over a selected period. It may carries a pen that lightly touches the paper sheet. The movement of the coil is traced on the paper sheet. The curve drawn on the paper shows the variation in the measurement of the electrical quantities. Data loggers such as temperature and humidity recorder