Bangladesh BEST Programme CONCEPTS OF METROLOGY AND IMPORTANCE OF CALIBRATION Nihal Gunasekara Sri Lanka
Bangladesh BEST Programme KEY WORDS Ø CALIBRATION – Comparison Ø METROLOGY – Science of Measurement Ø TRACEABILITY – Unbroken Chain of Comparisons Ø UNCERTAINTITY – Error in Measurement Ø ACCREDITATION – Third Party Ascertain Ø CALIBRATION INTERVAL – Equipment Remains Reliable
Bangladesh BEST Programme WHAT IS METROLOGY SCIENCE OF MEASUREMENTS Everything has to do with measurement Experiment or test Designing Conducting Analyzing Results CAN BE SEEN EVERYWHERE Allowing people to plan their lives and make commercial exchange with confidence within the Metrology realm 3
Bangladesh BEST Programme METROLOGY Ø Metrology Covers Three Main Tasks: Ø The definition of internationally accepted units of measurement Ø The realization of units of measurement by scientific method Ø Establishment of traceability chain in documenting the accuracy of a measurement “Metrology is essential in scientific research”
Bangladesh BEST Programme CATEGORIES OF METROLOGY Ø Scientific Metrology – Development of measurement standards Ø Industrial Metrology – To ensure the adequate functioning of measurement instruments used in industry, production & testing laboratories Ø Legal Metrology or Weights & Measures – Accuracy of measurement where these have influence on the transparency of economic transactions, health & safety
Bangladesh BEST Programme AREAS OF INDUSTRIAL METROLOGY Ø Mechanical Metrology – Realises , maintains and disseminates the national measurement standards in the areas of Mass, Volume, Pressure and Dimension Ø Electrical Metrology –– Realises , maintains and disseminates the national measurement standards in the areas of AC/DC, low frequency, time & frequency and temperature
Bangladesh BEST Programme LEGAL METROLOGY Ø Services offered by legal metrology are: Ø Mass measurements verification: verification of all mass measuring instruments (balances, trade masses etc. ) Ø Volume measuring instruments : verification of fuel dispensers, tankers , meters etc. Ø Prepackaging control : verification of quantities in prepackaged products (mass, volume, length, number etc. )
Bangladesh BEST Programme Calibration (Old Definition) “Calibration is the comparing of an unknown measurement device against equal or better known standard under specified conditions” 8
Bangladesh BEST Programme Calibration “Operation that, under specified conditions, in a first step, establishes a relation between the quantity values with measurement uncertainties provided by measurement standards and corresponding indications with associated measurement uncertainties, and in a second step, uses this information to establish a relation for obtaining a measurement result from an indication ” International Vocabulary of Metrology ) ( JCGM 200: 2012 – International Vocabulary of Metrology )
Bangladesh BEST Programme Units of Measurement SI Units published by BIPM(Bureau of Weights and Measures) Base Units… Quantity Unit Symbol Length metre m Mass kilogram kg Time second s Temperature kelvin K Electric current ampere A Luminous intensity candela cd Amount of substance mol 10
Bangladesh BEST Programme Metrology Laboratories Ø Primary Laboratories NML, NMI, NPL etc Ø Reference Laboratories Ø Calibration Laboratories 11
Bangladesh BEST Programme Measurement Uncertainty “ non-negative parameter characterizing the dispersion of the quantity values being attributed to a measurand, based on the information used” It arises due to the imperfections in the measurement system No measurement system is perfect !!!!! 12
Bangladesh BEST Programme Uncertainty An estimate of the possible error in a measurement Type A evaluation Type B evaluation The evaluation is carried out using available information found in calibration reports, certificates, specifications etc. 13
Bangladesh BEST Programme Expanded Uncertainty Calculate combined standard uncertainties Type A Type B Exp. Unc. U = Combined Uncertainty X Coverage factor 14
Bangladesh BEST Programme Ishikawa diagram Reference T/C Calibration (B) Digital Thermometer Resolution (B) Scatter (A) CJC (B) Uncertainty of an oven Test oven Resolution (B) 15
Bangladesh BEST Programme Confidence Level Gaussian probability distribution 68% 95% 99% -kσ +kσ Within 1σ of mean Within 2σ of mean Within 3σ of mean 16
Bangladesh BEST Programme Metrological Traceability ”property of a measurement result whereby the result can be related to a reference through a documented unbroken chain of calibrations, each contributing to the measurement uncertainty” or “HOW TO ENSURE THAT TWO MEASUREMENTS OF THE SAME QUANTITIES ARE COMPATIBLE” 17
Bangladesh BEST Programme How Do We Get Traceability ? Common point of reference My laboratory Your laboratory Their laboratory 18
Bangladesh BEST Programme NMI: The Link Organisation to the International Arena International standards National Metrology Institute National community that is using measurements 19
HIERACHY OF MEASUREMENT STANDARDS Bangladesh BEST Programme HIERARCHY OF MEASUREMENTS Primary Standards Traceable to BIPM Secondary Standards Working Standards Instruments Used in Lab/ Industry
Bangladesh BEST Programme Metal fixed-point Number Substances State Hg 1 Defining temperature K o. C T 234. 3156 -38. 8344 H 20 T 273. 16 0. 01 2 Ga M 302. 9146 29. 7646 3 In F 429. 7485 156. 5985 4 Sn F 505. 078 231. 928 5 Zn F 692. 677 419. 527 6 Al F 933. 473 660. 323 7 Ag F 1234. 93 961. 78 8 Au F 1337. 33 1064. 18 9 Cu F 1357. 77 1084. 62 21
Bangladesh BEST Programme CALIBRATION HIERARCHY OF MASS STANDARDS BIPM Kilogram National Kilogram Class E 1, E 2, F 1, F 2 Masses OIML M 1, M 2, M 3 Masses Analytical &Top loading Precision Balances OIML R 47 Masses TRADE MASSES Platform & Top loading balances Weighing Bridges 22
Bangladesh BEST Programme EXAMPLE MASS COMPARATOR Traceable to BIPM Prototype 1 kg USE Transfer Prototype 1 kg Traceable to SI Units Calibrate Analytical Balance Set of Classes E 2, F 1, F 2, and M 1 23
Bangladesh BEST Programme GAUGE BLOCK COMPARATOR Primary Standard Traceable to Laser interferometer Compare USE Grade K set Calibrate Grade 1 set 24
Bangladesh BEST Programme Examples 1. Performance Test on a Incubator at 35 + 0. 5 o. C Set Temp. Indicator Value o. C Expanded Uncertainty Measured Mean value o. C Min 34. 5 Max Near Sensor Upper Middle Lower 34. 5 34. 6 34. 9 34. 7 34. 5 34. 2 o. C 0. 2 25
Bangladesh BEST Programme 2. Performance Test on a Water Bath at 50 o. C Set Temp. Indicator Value Measurement o. C Locations Min 49. 5 48. 0 Max 50. 0 Measured Mean Value R 50. 1 S Q 50. 1 R S 50. 2 Q o. C 50. 1 P P C C Expanded Uncertainty 50. 0 1 Uniformity : 0. 61 o. C Stability : 0. 33 o. C 26
Bangladesh BEST Programme MASS Reference and Auxiliary Equipment Ø COMPARATOR BALANCES Ø Ø Ø CLASS CLASS E 1 1 kg E 1 SET E 2 SET F 1 SET F 2 SET M 1 SET 27
Bangladesh BEST Programme CALBRATION INTERVALS What is Calibration interval ? ? ? Period of time of use to ensure the equipment remains reliable Interval is too short : Calibration $$$$$ Interval too long : Risk of bad measurements 28
Bangladesh BEST Programme CALBRATION INTERVALS ISO 17025 Requirements: ØCapable of achieving required accuracy ØComply with specifications relevant to test/calibration method ØUse under established calibration programme Therefore need to : ØDefine required accuracy ØIdentify the equipment that can affect it ØManage all equipment under a calibration programme 29
Bangladesh BEST Programme RECOMMENDED CALBRATION INTERVALS N No single correct answer Calibration represents an instantaneous snapshot of actual condition Depend upon v. Level of stress - subjected v. Stability of past calibration v. Allowable tolerance range v. Required accuracy v. Quality Assurance Requirements 30
Bangladesh BEST Programme RECOMMENDED CALBRATION INTERVALS Final Analysis Period between two calibrations Determined & Monitored USER HIMSELF 31
Bangladesh BEST Programme HOW TO ESTABLISH CALIBRATION INTERVAL Consider influencing factors and existing knowledge : eg v. Accuracy sought & consequences of error v. Manufacture’s recommendations v. Accommodation & environment v. Purpose and usage v. Maintenance & servicing v. Trends from previous calibration v. Frequency of checks v. Etc. etc. …. Ref. - ILAC – G 24 : Guidelines for determination of calibration interval of measuring instruments 32
Bangladesh BEST Programme RECOMMENDED PRACTICES Ø Calibration at (planned) periodic intervals to ensure acceptable accuracy & reliability Ø Shorten the intervals when results of previous calibration suggest it Ø May lengthen intervals on basis of demonstrated performance Ø Documented procedure for assigning and adjusting calibration intervals Ø Fully documented re-calibration system 33
Bangladesh BEST Programme CALIBRATION OF VOLUMETRIC GLASSWARE Ø FLASKS Ø CYLINDERS Ø BURETTES Ø PIPETTES ACCURACY CLASSES CLASS A – Higher grade CLASS B – Lower grade 34
Bangladesh BEST Programme Example - Pipettes Nominal capacity(ml) Limit of Error (ml) Class A Class B 1 0. 008 0. 015 25 0. 03 0. 06 100 0. 08 0. 15 200 0. 1 0. 2 METHOD Gravimetric Method – IS 0 4787 -2010 (Laboratory Glassware- Volumetric instruments- Method of Testing of capacity and for use) 35
Bangladesh BEST Programme IN-HOUSE PERFORMANCE CHECKS (During Calibration Interval) v ANALYTICAL BALANCES – Using a Calibrated Weight v INCUBATORS - Using a Calibrated Thermocouple v GLASS THERMOMETERS- Ice Point 36
Bangladesh BEST Programme Importance of Calibration Ø Assurance of accurate of measurements Ø Ability to trace measurements to International standards Ø International acceptance of test/calibration reports Ø Correct diagnosis of illness (medical reports) Ø Consumer protection (legal metrology) Ø Meeting the requirements of ISO 9000 and 17025 37
Bangladesh BEST Programme How we ensure Technical Competence of Calibration Laboratories & Measurements are traceable to SI Units ACCREDITATION 38
Bangladesh BEST Programme Defined Criteria for Laboratory Accreditation Metrology Laboratory • Organization • Laboratory Quality System • Qualified personnel • Range of the work capabilities and test methods • Laboratory practices and management system • Reliable standards and measuring devices • Laboratory facilities • Adequate measuring capabilities • Traceability maintenance • Calibration records • Satisfactory completion of internal audits
Bangladesh BEST Programme QUALITY SYSTEM ISO/IEC 17025 v QUALITY MANUAL v PROCEDURE MANUAL v METHOD MANUAL v FACILITIES MANUAL v SAFETY MANUAL 40
Bangladesh BEST Programme ACCREDITED LABORATORY Ø IMPLEMENTATION OF ISO 17025 MANAGEMENT REQUIREMENTS TECHNICAL REQUIREMENTS Ø TRACEABILITY Ø MAINTENANCE OF ENVIRONMENTAL CONDITIONS Ø TRAINED STAFF 41
Bangladesh BEST Programme ENVIRONMENTAL CONDITIONS ØTEMPERATURE ØHUMIDITY ØAIR VELOCITY ØFREE OF VIBRATION ØILLUMINANCE 42
Bangladesh BEST Programme ACCREDITED MASS LABORATORY ENVIRONMENTAL CONDITIONS: TEMPERATURE: 23 ± 0. 5 0 C , HUMIDITY : 50 ± 10% 43
Bangladesh BEST Programme ACCREDITED TEMPERATURE LABORATORY ENVIRONMENTAL CONDITIONS: TEMPERATURE: 23 ± 1 0 C , HUMIDITY : 50 ± 10% 44
Bangladesh BEST Programme CONTENTS OF CALIBRATION CERTIFICATE Ø Ø Ø Ø Ø NAME AND ADDRESS : CUSTOMER/ LABORATORY METHOD CONDITION RECEIVED IDENTIFICATION DATE OF CALIBRATION DATE OF RECALIBRATION ? CALIBRATION RESULTS UNCERTAINTY OF MEASUREMENT TRACEABILITY ENVIRONMENTAL CONDITION 46
Bangladesh BEST Programme SAMPLE OFSCOPE OF ACCREDITATION CALIBRATION RANGE m. L C. M. C m. L • ONE MARK PIPETTE 0 to 200 0. 01 • GRADUATED PIPETTE 0 to 25 0. 001 • BURETTE 0 to 200 0. 01 • VOLUMETRIC FLASK 0 to 2000 0. 01 • GRADUATED MEASURING CYLINDER 0 to 2000 0. 01 47
Bangladesh BEST Programme Accredited Metrology Facilities Ensure Traceable Measurements Technical Competency Industries Better Place in Global Market ISO Certified QMS Products Quality Life 48
Bangladesh BEST Programme “Calibration of laboratory equipment is important to obtain reliable test results” 49
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