Downloaded 20 times
Uploaded byHassan Habib
Basics of Dimensional Metrology
The document discusses dimensional metrology, which includes fundamental concepts such as accuracy, precision, and measurement errors, along with the importance of validation and verification in measurement processes. It outlines the inspection process, types of measurements, and essential terminology related to measurement systems. Additionally, it emphasizes the need for regular review and the adherence to standards to ensure measurement reliability and consistency.
More Related Content
Similar to Basics of Dimensional Metrology
Basics of Dimensional Metrology
- 1.
- 2. Table of Contents •Introduction • Basic Terminologies • Inspection Process • Measurement Process Validation
- 3. Introduction • In 1999NASA sent a mission to MARS • Climate Orbiter • It completed its 99% of journey • Fired steering rocket to control its final approach • However, the thrust value had a Martian Blunder
- 4. Introduction • 1776 warof independence • Had to deliver 10000 muskets in two years • With no factory • Did it in 10 years • Then took the order of 15000 muskets and delivered them in two years Eli Whitney Order of Muskets
- 5.
- 6. “When you measurewhat you are speaking about and express it in numbers, you know something about it, but when you cannot express it in numbers your knowledge is of a meagre and unsatisfactory kind...” Lord Kelvin (1824~1907) Introduction The need
- 7. As a resultof its importance, measurement has a science of its own, called metrology, from the Greek words metron (‘measure’) and logos (‘study’) Introduction Metrology
- 8.
- 9. BASIC TERMINOLOGIES Error &Uncertainty Error is the difference between the measured value and the true value of the thing being measured Uncertainty is the parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand. Whereas,
- 10. BASIC TERMINOLOGIES Accuracy &Precision
- 11. BASIC TERMINOLOGIES Resolution The resolutionof an instrument is a quantitative expression of the ability of an indicating device to distinguish meaningfully between closely adjacent values of the quantity indicated.
- 12. BASIC TERMINOLOGIES Trueness Trueness isa similar concept to accuracy, but while accuracy refers to the closeness between an individual measurement and the true value, trueness refers to the closeness of agreement between the average value obtained from a set of test results and the true value.
- 13. BASIC TERMINOLOGIES Repeatability Repeatability isthe closeness of agreement between repeated measurements of the same thing, carried out in the same place, by the same person, on the same equipment, in the same way, at similar times.
- 14. BASIC TERMINOLOGIES Reproducibility Reproducibility isthe closeness of agreement between measurements of the same thing carried out in different circumstances, e.g. by a different person, or a different method, or at a different time
- 15. BASIC TERMINOLOGIES Confidence Level Makea number of measurements of something – like the concentration of carbon monoxide gas in your vicinity – True value lies between, say, 9 parts per million (ppm) and 11 ppm – probably (or 10±1 ppm). You could not be sure that this was the case, but you could express your confidence that it is. So you might decide that you are 90% confident that the answer lies between those values.
- 16. BASIC TERMINOLOGIES Tolerance A toleranceis the maximum acceptable difference between the actual value of some quantity, and the value specified for it.
- 17. BASIC TERMINOLOGIES Validation Validation isconfirmation that some aspect of a measurement process is fit for purpose. Verification Verification is making measurements to ensure conformance to specifications.
- 18. BASIC TERMINOLOGIES Calibration Comparison ofan instrument against a more accurate one (or against a reference signal or condition), to find and correct any errors in its measurement results.
- 19. BASIC TERMINOLOGIES Accreditation Accreditation isthe independent, third-party evaluation of a conformity assessment body (such as certification body, inspection body or laboratory) against recognised standards, conveying formal demonstration of its impartiality and competence to carry out specific conformity assessment tasks (such as certification, inspection and testing).
- 20. BASIC TERMINOLOGIES Certification Certification isthe provision by an independent body of written assurance (a certificate) that the product, service or system in question meets specific requirements.
- 21. INSPECTION USES • DocumentChanges in process performance • To distinguish between good lots and bad lots • Distinguish between good product and bad product • Determine status of process control • Evaluation of process capability / adjustment of process • To rate accuracy of inspectors / inspection equipment
- 22. INSPECTION PROCESS What to measure? Instrument Selection Knowledge ofMSA Rounding Rules Inspection Stage Errors in inspection Sampling Regular Review Traceability of Inspections
- 23. INSPECTION PROCESS What tomeasure? • Measurement is made for a reason • It needs to be defined and understood • Only then can a right measurement be made
- 24. INSPECTION PROCESS What tomeasure?
- 25.
- 26. INSPECTION PROCESS Knowledge ofMSA • Measurement System Validation • Repeatability & Reproducibility (ISO5725-1,2: 2019) • Uncertainty of the measurement (ISO 21748: 2017) • Proficiency Testing • Comparison with other results
- 27. INSPECTION PROCESS Knowledge ofMSA (ISO14253)
- 28. INSPECTION PROCESS Knowledge ofMSA (ISO14253)
- 29. INSPECTION PROCESS Rounding Rules(ASTM E29)
- 30. INSPECTION PROCESS Rounding Rules(ASTM E29)
- 31. INSPECTION PROCESS Sampling Sr. #Characteristic MIL-STD- 105 E MIL-STD-1916 ISO 2859 ISO 3951 1. Basics Attributes Attribute / Variables Attributes Variables 2. Acceptance Criteria # of Non Conformin g products / AQL # of Non Conforming Products or s- characteristic / verification levels No. of Non Conforming Products / AQL S- characteristi c / AQL 3. Distribution Any Any Any Normal only 4. Sample Sizes Standard Tables Follows 105 E Follows 105 E Different (usually smaller) 5. Switching Standard Follows 105 E Slightly Different Different
- 32. INSPECTION PROCESS Inspection stages •Incoming • Final • Pre Process • Post Process • Verification Inspection
- 33.
- 34.
- 35.
- 36.
- 37.
- 38.
- 39. INSPECTION PROCESS Regular Review •Check Instruments • Check Measurement Procedures • Inspection Audit
- 40. INSPECTION PROCESS Inspection Traceability •Keeping Controlled Records
- 41. Six Guiding Principles RegularReview • Check Instruments • Check Measurement Procedures Demonstratable Consistency • Gauge R&R Studies • Proficiency Testing • Regularly Analyse factors that could effect measurements
- 42. Six Guiding Principles TheRight Procedures • Written Procedures of measurement • Include risk assessment in the procedure
- 43. Building Blocks ofMeasurement System Analysis 1. Measurement System Validation a) Accuracy (ISO 5725-1: 2019) b) Repeatability & Reproducibility (ISO 5725-2: 2019) 2. Uncertainty Assessment (ISO 21748:2017) 3. Comparison of results with other methods 4. Proficiency Testing