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Mass (Weight)= 98.27grams
Length= 11.1cm
Speed= 60km/h
Temperature=37.0⁰ Celsius
Volume=43ml
Pressure Reading=0.00 Psig
“No Instrument is Correct”
Presented ByUsman Islam ( 2012-Ch-01 )
Metrology
Science of measurement. 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”
Some Terminology
Absolutely Exact Value True value Measured value Error
Significant figures
Those digits 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.
Accuracy and Precision
Accuracy Precision – Reproducibility of results
Even if all the errors are neglected, the measurement’s accuracy of an instrument is limited by it’s Least Count
What is Least Count
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
Least Count
For graduated scales calculated using the simple formula
Least Count= (Value Measured in “n” divisions) / (Number of divisions “n”)
Where n= Smallest divisions
Exercise: Determine the least count
Convincing Point The number “ π “ or “Pi” Circumference of circle=2πr Radius=r Diameter=2r The ratio of a circle's circumference to
its diameter.
First 100 digits of number “Pi”
3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679
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.”