8. 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”
10. 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.
13. Even if all the errors are neglected, the
measurement’s accuracy of an instrument is
limited by it’s Least Count
14. 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
15. 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
17. 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.
18. First 100 digits of number “Pi”
3.14159265358979323846264338327950288419
716939937510582097494459230781640628620
89986280348253421170679
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.
Assumed correct value
3 significant figures
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
Even if we have the most accurate system it cannot be the absolute correct value
Errors systematic, Random, weather, zero, parallax
Very very lesser extent but still
Least Count tells you the minimum reading or value that can be measured with a measuring tool or device.
We never know who discovered ratio of a circle's circumference to its diameter constant
Egyptians, nearly 4000 years ago named the constant PI.