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No instrument is Correct
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- 7. “No Instrument is Correct” PresentedBy Usman Islam ( 2012-Ch-01 )
- 8. Metrology Science ofmeasurement. Embracing both experimental and theoretical determinations. Measurement is the process of determining Measuring instruments are measuring devices “A measurement is not very meaningful without an error estimate”
- 9. Some Terminology AbsolutelyExact Value True value Measured value Error
- 10. Significant figures Thosedigits in an observed quantity (measurement) that are known with certainty plus the one digit that is uncertain or estimated Depends on smallest division on a measuring tool Example the ruler shown reads 1.3 cm with certainty and 1.35cm with uncertainty.
- 11. Accuracy and Precision Accuracy Precision – Reproducibility of results
- 13. Even if allthe errors are neglected, the measurement’s accuracy of an instrument is limited by it’s Least Count
- 14. What is LeastCount The smallest value that can be measured by the measuring instrument is called its least count. A measuring instrument can not measure any thing whose dimensions are less than the magnitude of least count Measured values are good only up to this value The least count error will always be present in measurements
- 15. Least Count Forgraduated scales calculated using the simple formula Least Count= (Value Measured in “n” divisions) / (Number of divisions “n”) Where n= Smallest divisions
- 16. Exercise: Determine theleast count
- 17. Convincing Point Thenumber “ π “ or “Pi” Circumference of circle=2πr Radius=r Diameter=2r The ratio of a circle's circumference to its diameter.
- 18. First 100 digitsof number “Pi” 3.14159265358979323846264338327950288419 716939937510582097494459230781640628620 89986280348253421170679
- 19. References http://www.chemteam.info/SigFigs/Measuring.html http://www.regentsprep.org/regents/math/algebra/am3/LError.html http://www.wikipedia.com http://www.miniwebtool.com/first-n-digits-of-pi/?number=100 http://www.slideshare.com http://merryquest.blogspot.com/2014/05/best-way-to-find-least-count-of.html “Error does not mean blunder or mistake. Rather it signifies accuracy.”
Editor's Notes
- #2 Electronic balance
- #8 Before Least Count some other terms
- #9 utilise a measuring sequence in which the measured quantity is transformed into a quantity perceptible to the observer Instrument – a device or mechanism used to determine the present value of a quantity Measurement – a process of comparing an unknown quantity with an accepted standard quantity.
- #10 Assumed correct value
- #11 3 significant figures
- #12 Degree to which the measurement conforms to the correct value. Limited by the instrument used Precision refers to the closeness of two or more measurements to each other. Limited by the skill of the observer
- #13 Even if we have the most accurate system it cannot be the absolute correct value
- #14 Errors systematic, Random, weather, zero, parallax Very very lesser extent but still
- #15 Least Count tells you the minimum reading or value that can be measured with a measuring tool or device.
- #18 We never know who discovered ratio of a circle's circumference to its diameter constant Egyptians, nearly 4000 years ago named the constant PI.