Factors in Measurement , Lab Care and Safety

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Some of the important considerations in the process of measurement are described here.
  1. Accuracy : By Employing a suitable tool a measure of a physical quantity can be known. The reading's accuracy depends on two factors. The device as well as the person who takes the measurement. Therefore accuracy can mean the degree up to which a measured value conforms with a standard or true value.
  2. Least Count : A measuring instrument's accuracy depends upon its least count. Least count of the instrument is the least distance which it can measure accurately.
  3. Measuring instruments such as vernier callipers, micrometer, screw gauge, etc. show different levels of accuracy in comparison to each other. For example the least count of a screw gauge is 0.01mm while that of a vernier calliper is 0.1mm.
  4.  Significant Figures : Significant figures refer to those digits about which we are perfectly sure of plus those digits about which we are not that sure. However, they have a value which is meaningful. This also gives insights concerning the extent of uncertainty in measurement. To give an example the value of p (pi) is 3.1415926 = circumference/diameter Generally the experiments show answer upto 3.14 while the balance digits can vary due to alteration in the value adopted for circumference and diameter and that's why there is rounding off to 3 digits.
  5. Sensitivity of the Instrument : TSensitivity of the instrument refers to the instant reaction of an instrument, indicating the measurement at a particular instance of use
  6. Hysteresis : The measuring instrument should be devoid of any prior recording or reading, and must give identical values for ascending or descending readings.
  7.  Precision : Precision refers to the degree to which a given set of measurements of the identical amount concur with their mean value, but which will not be true value.
  8. Errors : Error is the difference that exists between the true value and the measured value. There are many types of errors, some of which are given here.
  • Systematic error
  • Environmental error
  • Human error
  • Random error
  • Absolute error
  • Gross error
  • Mean absolute error
  • Relative and percentage error

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