MEASUREMENT TECHNIQUES
Academic year and teacher
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- Versione italiana
- Academic year
- 2022/2023
- Teacher
- MICHELE PINELLI
- Credits
- 6
- Didactic period
- Primo Semestre
- SSD
- ING-IND/08
Training objectives
- The course will provide knowledge about the most frequently techniques used in the measurement of the main fluid flow and thermal quantities of industrial and energy interests in engineering . In the course the working principles of measuring instruments and the basis for the execution of the measures are shown. Additional in-depth techniques and tools for a critical evaluation of the quality of the measures through the analysis and evaluation of measurement uncertaintiesare shown
The course also aims to provide students with the necessary skills to deal with the design of a measurement system including the selection, installation requirements, the procedure of use and assessment of the quality of the instruments and their measurement chain, taking into account technical and economic constraints arising from practical knowledge of commonly used tools in the industrial field. Prerequisites
- Prerequisites: Calculus and Geometry, Physics, Industrial Technical Drawing, General Physics I. Basic knowledge of Technical Physics, Energy Systems are recommended and it is assumed that major statistical concepts and probability are you have known or partially known. Finally, it is noted that, since they are provided for in the lab exercises, you must acquire the training on safety in the workplace
Course programme
- Introduction to the course. Measurement concept. Transfer function. Process of measuring a quantity.
Definition of measurement: number, uncertainty, measurement unit. Unit of measurement. Introduction to measurement uncertainty. True value and measurement error.
Error sources: systematic and random. Definition of measurement uncertainty. Uncertainty assessments: type A and type B. Extended uncertainty.
Derived uncertainties: law of propagation of uncertainties. Measurement chain.
Notes on dynamic behavior of instruments. Static behavior of instruments. Static calibration. Traceability. Calibration Documents: Certificate and Report.
Calibration curves. Least squares method. Measuring instruments: Definitions. Sensitivity. Measurement errors: linearity, hysteresis, repeatability. Standard accuracy. Other errors. Extended accuracy.
Rules of indication of instrumental accuracy. Temperature measurements. Units of measurement. The International Temperature Scale.
Expansion thermometers: measurement chain. Solid, liquid and gas thermometers. Resistance thermometer. Definition. Measurement chain. Transfer function. Materials.
Measurement chain. The EN 60751 standard. Tolerance classes. Acceptability. Wheatstone bridge at equilibrium and unbalance.
Wheatsone bridge for RTD measurements. 2-wire, 3-wire and 4-wire connections. . Thermistors.
Thermocouples: principle of operation. Thermoelectric effects. Practical laws of thermocouples. Measurement chain. Reference joint: methods. Single metal calibration curves.
Thermocouple calibration curves. Common thermocouples. Extension and compensation cables. The IEC 584 Standard. Tolerance classes.
Calibration of insertion temperature instruments. Installation errors in insertion temperature measurements. Conduction error.
Error due to irradiation. Speed effect error. Radiation measuring instruments. Notes on the laws of radiation.
Total irradiation and partial irradiation pyrometers. Measurement problems in pyrometers: emissivity in total irradiation pyrometers. Emissivity uncertainty. .
Measurement problems in pyrometers: emissivity in partial irradiation pyrometers, pointing and disturbances from other sources. Methods for the determination of emissivity. Pressure measurements: definition of the quantity.
Pressure unit of measurement. Mechanical and electrical pressure transducers. Bourdon tube. The potentiometer. Ideal solution. Real solution and loading effect. Sensitivity and resolution.
Strain gauges. Theoretical strain gauge coefficient. Construction types of strain gauges. Characteristics of strain gauges: coefficient of experimental strain gauges.
Characteristics of strain gauges: transverse sensitivity, interfering temperature effects, self-compensation, modifying temperature effects. Wheatstone bridge applied to strain gauges. Special configurations: temperature compensation.
Special configurations: sensitivity increase, effects selection. Pressure instruments configuration. Mutual inductance transducers: LVDT. Capacitive transducers. Piezoelectric transducers. Installation requirements.
U-shaped manometers. Tank and inclined tube manometer. Calibration of pressure instruments: for comparison. Dead weight manometer. Total pressure measurements: Pitot tube.
Velocity measurements: Pitot-Prandtl tube. Flow measurements: general information. Flow measurements through velocity measurements. Averaged Pitot tube. Obstruction flow measurements. Laminar Flow Element.
Obstruction devices (diaphragm, nozzle, Venturi). The UNI ISO 5167 standard. Transfer function. The efflux coefficient. Iterative process. Installation requirements. Measurement chain. Uncertainty.
Volumetric flow meters. Flow-error diagram. Electromagnetic, vortex shedding, ultrasonic meters. Mass flow meters. Coriolis meter, thermal (hot wire). Didactic methods
- Lectures and applied activities.
Learning assessment procedures
- The exam includes a written test on theory and one or more practical applications of the theory.
The final evaluation is based on the theoretical and on the verification of the student ability to solve a numerical problem application. The theoretical part and the exercise have the same weight in the final evaluation. It is also always verified the ability to perform conversions of measurement units. The latter, if not succeeded, determines the examination fails regardless of the outcome of the other questions. Reference texts
- Didactical texts
P.M. Azzoni - Strumenti e misure per l'ingegneria meccanica - Hoepli
R.S. Figliola, D.E. Beasley – Theory and Design for Mechanical Measurements
G. Rossi - Misure meccaniche e termiche - Carocci
Insights
G. Minelli – Misure Meccaniche - Patron - Bologna
P.H. Sydenham - Handbook of Measurement Science – John Wiley and Sons – New York
E. O. Doebelinn - Measurement Systems - Mc Graw Hill – New York
H. W. Coleman, W.G. Steele - Experimentation, Validation, and Uncertainty Analysis for Engineers, Wiley
