Unit i mm (1)
- 2. GENERAL APPLICATIONS • Design and drawing • Production planning • Manufacturing • Assembly section • Research and development • Prizing • Packaging • Marketing • Surveying • Banking • Medical metrology • Food factory's • Oil industry’s • Piping • Textile industry's • Environment • Austhetic 2
- 3. METROLOGY AND MEASUREMENTS • UNIT I – Basics of Metrology • UNIT II – Linear and Angular Measurements • UNIT III – Advances in Metrology • UNIT IV – Form Measurements • UNIT V – Measurement of power, Flow and Temperature 3
- 4. UNIT-I BASICS OF METROLOGY Introduction to metrology-Need- Element Work piece, Instruments- Persons-Environment-Their effect on precision and accuracy-Errors-Errors in measurement-Types-Control-Types of standards. 4
- 5. INTRODUCTION TO METROLOGY • Science of measurement • Ensuring uniformity of measurement • Developing new methods of measurement • Analyzing new methods • Gauges design, manufacturing and testing • Changing units in the form of standards • Researching cases and industrial inspection 5
- 7. NEED FOR METROLOGY • To determine true dimensions • To ensure public health and human safety • To evaluate the performance of a system • To study the basic laws of nature • To check the limitations of theory in practical situation • To design and finding new data 7
- 8. METHODS OF MEASUREMENT • Direct comparison (length, mass. time) Primary measurement Secondary measurement (single conversion) Tertiary measurement (more than one conversion) • Indirect comparison • Comparative (using comparators) mechanical, electrical, hydraulic, pneumatic types 8
- 9. METHODS OF MEASUREMENT • Coincidence (Certain Values and signals) • Fundamental • Contact ( Sensor and Measuring tip) • Transposition • Complementary (Volume determination) • Deflection (pressure measurement) 9
- 10. Direct Method 10
- 11. 1. Primary sensing element (receives energy as input signal) 2. Variable conversion element (without changing) 3. Variable manipulation element (magnification) 4. Data transmission element (transmit from one element to other) 5. Data processing element (modify the data before displayed) 6. Data presentation element (monitoring) 11 GENERALIZED MEASURING ELEMENT SYSTEM
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- 13. BOURDON TUBE PRESSURE GAUGE 13
- 14. UNITS • M.K.S,CGS &S.I • System International Fundamental units-Length, Mass, Time, Temperature, Electric current & Luminus intensity. Supplementary units-radian, steradian Derived units-A,V,Density,v,a,F,P,W,p 14
- 15. STANDARD • Physical representation of unit of measurement • The term standard is used to denote universally accepted specifications for devices. • Components or processes which ensure conformity and interchangeability throughout a particular industry. • A standard provides a reference for assigning a numerical value to a measured quantity. 15
- 16. TYPES OF STANDARD • International standards (Internationally accepted) • Primary standards ( National Physical Laboratory at New Delhi) • Secondary standards(Basic reference standard) • Working standards(To check the components) 16
- 17. Measuring Instruments • Deflection and null type • Analog and Digital Instruments • Active and passive type instruments • Automatic and Manually operated instrument • Absolute and secondary instruments (Galvanometer) • Contacting and non- contacting instruments • Intelligent instrument (Remote operated) 17
- 20. ACCURACY • The degree of closeness of a measurement compared to the expected value is known as accuracy. • It refers how closely the measured value agrees with the true value. • Accuracy as “Percentage of Full Scale Reading”: In case of Instruments having Uniform scale Percentage of Full Scale Reading=Measured value- True value/Maximum Scale Value 20
- 21. Accuracy (Cont….) • Accuracy as “Percentage of True Value” It is way of specifying the accuracy. True value of quantity to be measured. Percentage of True Value=Measured value-True value/True value • Accuracy as “Percentage of scale span”: • qmax=Maximum point sacle is calibrated • qmin=Minimum scale reading • qmax-qmin=Scale span Example:±0.1%-Accuracy Range-10 to 150 units Scale Span=±0.1(150-10)/100=±0.14 uints errors 21
- 22. Precision • Precision is the degree of exactness for which an instruments is designed or intended to perform. • It refers the repeatability or consistency of measurements. • They have two characteristics: • i).Conformity ii).Significant Figures • Conformity:There are no deviations from observed value,the error created by the limitation of the scale reading is called as precision error. • Example:2834267Ώ • Multimeter indicates 2.8M Ώ 22
- 23. PRECISION • Significant Figure: It Conveys the actual information regarding the magnitude and the measurement precision of a quantity. • Significant figure is the number of digits for measuring output • Example:Voltage 240V • Closer valve 240V or 239V or 241V (3 Values) • Significant figure 240.0V or 239.9V or 240.1V 23
- 26. Accuracy Vs Precision • Example:100Mpa with Pressure Gauge • Six Readings are taken 103,104,102,103,102,104 Mpa • Average 103,Max Deviation ±1 Mpa • Instrument Calibrated ±1 Mpa. • Accuracy(104-100/100)=4% • Precision ±1% • High Precision Poor Accuracy 26
- 29. SENSITIVITY • Is Defined as the ratio of magnitude of output Signal to the magnitude of input signal. • Input-output relation is linear means Constant for all values of input. • Non-Linear means instruments depends on the value of the input quality. 29
- 30. SENSITIVITY 30 • Sensitivity has no unique unit. • Which is dependent on the instrument. • Some of units of sensitivity millimeter per micro- ampere,millimeter per ohm,counts per volt,ohms per degrees celsius.
- 31. SENSITIVITY 31
- 35. Stability • The ability of a measuring instrument to retain its calibration over a long period of time is called stability. • Stability is the key to predictability. • Used to determined by control chart. • Repeated measurements are taken by instruments. • Measurement system robust to the condition. 35
- 36. READABILITY • Readability is defined as the closeness with which the scale of analog instrument can be read. • Present Days Industry are preferred digital type instrument not analog instruments. • Readability depends on both the instruments and observer • Examples: Weighing Scale, Thermometer 36
- 38. REPEATABILITY • Repeatability is defined as the closeness of agreement among the number of consecutive measurement of the output for the same value of input under the same operating conditions. 38
- 39. REPEATABILITY 39 • In diagram shows input and output relationship curve with positive and negative reputability. Reproducibility: Reproducibility is defined as the closeness of agreement among repeated measurements measurement of the output for the same value of input under the same operating conditions over a period of time.
- 40. Reproducibility • Reproducibility and repeatability are the measures of the closeness to a given input may be measured again and again. • Reproducibility defined two terms: (i).Stability-Comapred to the time taken for reading the measurement (ii).Constancy-Constant input testedmesurement are allowed to vary within the specified limits. 40
- 41. ERRORS 41 Difference between the measured value and true value True absolute error: It is the algebraic difference between the result of measurement and the conventional true value of the quantity measured. Apparent absolute error: If the series of measurement are made then the algebraic difference between one of the results of measurement and the arithmetical mean is known as apparent absolute error.
- 43. Relative Errors • Relative errors is defined as the results of the absolute error and the value of comparision used for the calculation of absolute error. • Comparison may be true value or conventional true value or arithmetic mean for series for measurement. 43
- 44. TYPES OF ERRORS • STATIC ERROR Characteristic error Reading error Environmental error • LOADING ERROR • DYNAMIC ERROR Systematic error i) Calibration errors ii) Ambient or Atmospheric conditions iii) Avoidable Error iv) stylus pressure Random error 44
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- 52. Correction and Calibration • Correction is defined as a value which is added algebraically to the uncorrected result of measurement to compensate for an assumed systematic error. • Calibration is the process of determining and adjusting an instruments accuracy to make sure its accuracy is within the manufactures specifications. 52
- 53. CALIBRATION 53
- 54. Questions? 54