1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Error Calculation in Multiplication of two measurement points

  1. Apr 23, 2012 #1
    1. The problem statement, all variables and given/known data
    Hi All, I have a problem in calculating the thickness of a coating material inside a tube. The tubes inside diameter is measured before and after coating. The coating thickness is calculated by substracting the diameters and dividing by two to get the thickness of the coated material. The before coat diameter is 0.3949". The after coat diameter is 0.3893". The measurement error's standard deviation is 0.00017". I need to calculate the coating thickness value and its associated error.


    2. Relevant equations
    Coating Thickness = (Before Coat Dia. - After Coat Dia.)/2


    3. The attempt at a solution
    I am thinking the thickness without error = (0.3949 - 0.3893)/2 = 0.0028"

    My error for each measurement would be measured value +/- 3 x the Standard Deviation Error.
    For uncoated = 0.3949" +/- 0.00051"
    For Coated = 0.3893" +/- 0.00051

    The minimum thickness = (0.3949 - .00051) - (0.3893 + 0.00051) = 0.00458"

    The maximum thickness = (0.3949 + 0.00051) - (0.3893 - .00051) = 0.00662"

    Error Thickness = (.00662 - 0.00458)/2 = 0.00102"

    Coating Thickness = 0.0028" +/- 0.00102"?
     
  2. jcsd
  3. Apr 23, 2012 #2

    tms

    User Avatar

    There are standard formulas for doing this. Look up 'propagation of errors' in Bevington or some similar book.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Error Calculation in Multiplication of two measurement points
Loading...