Metrology-2-National Measurement System Flashcards
what place holds physical measurements?
National Physical Laboratory(NPL)
Some Physical measurements?
Environmental, Optical Radiation, Radio, Microwave and Acoustics, Mass, Length, Force, Pressure, Colour, Gas Standards
What measurements do the National Engineering Laboratory hold?
Gas, Water, Oil and Multiphase Mixtures
What do the Laboratory of the Government Chemist do?
Proficiency Testing schemes, Gas Standards, Certified Reference Materials
What do the Office for Product Safety and Standards do?
*Trade Measurements
*Type Approval
*Equipment testing
*Mass, Length and Volume calibration
*EMC Testing
*Traceability
*Trading Standards
Who is in charge of Laboratory Accreditation?
United Kingdom Accreditation Service(UKAS)
What is Measurement Traceability?
*Ability to trace the result of a measurement to a single source that is a national, or more likely, an international standard.
What to all industrialised countries typically have?
A National Bureau of Standards
Rules when tracing between measurement and NPL?
The traceability chain must be unbroken, usually involving working and transfer standards.
What is the Traceability Chain?
1.Instrument/ Measuring Process eg. Micrometer
2. Working Standards eg. Class 2 Gauge Blocks
3. Secondary/Transfer Standards eg. Class 0 Gauge Blocks
4. NPL National Standards
eg. Definition of the Metre
Cost increases with the number
What do companies do when they cant afford their own calibration laboratories?
Use outside accredited laboratories for the transfer standards and calibration
What are the differences between transfer standards, Measurement Instruments and working standards?
- 10x difference of accuracy between all of them starting with Transfer standards as the most accurate.
- Transfer and Working Standards require periodic calibration.
What do UKAS accredited laboratories give out?
Guaranteed traceable calibrations to national standards(measurements), with statements of uncertainty.
What is the purpose of calibration?
To provide confidence about a measurement instruments accuracy and repeatability.
What should calibration be?
Traceable via UKAS accreditation
What is calibration also about?
The instrument, but also information handling, data analysis, intervals, uncertainties/error analysis, environment and people
What is the error due to the calibration process?
Should be a maximum of ten percent of the permissible error of the instrument or measuring process being calibrated.
10x rule again
Calibration environment is difficult to control and is a function of ?.
Temperature, humidity, electrostatic fields, human interaction, pressure, vibration, electromagnetic fields
Calibrator must be aware if all potential sources of error which could affect calibration
What may a calibration process involve?
Not just single measurements which are quick but more than likely many measurements across time. Stability is required in these cases.
