Inspiration for this project is from two other measuring machines.  One of these is a commercial measuring machine manufactured by Pratt & Whitney and the second is the NIST Length Scale Interferometer.

(http://www.prattandwhitney.com/images/customer-files/measuring_systems1.pdf) This machine is a Metrology Laboratory Measuring Machine, which are able to be certified traceable to NIST, and is able to measure up to 120 inches with one micro inch resolution.It uses a Hewlett Packard 5528A laser interferometer system as it’s measuring system.This is convenient since over the last few years I have collected many of the individual components of a HP5528A system from online auctions and other online sources.This Pratt & Whitney measuring machine has most of the features that I would like to end up with my project.

My second source of inspiration for this project is the saga of the history, design and evolution of the NIST Length Scale Interferometer.http://www.nist.gov/calibrations/upload/104-225.pdfThis document describes the efforts of the United States National Bureau of Standards (now known as NIST) efforts to design and build a Laser Interferometer Measuring Machine.Original experimentation and construction of a laser interferometer began sometime around 1958 and by 1961 researchers had built a measuring machine capable of measuring across a range of about 10 centimeters.Major changes to the interferometer occurred in 1965 and 1966 with advancements in laser construction.Finally in 1979 the NIST Length Scale was integrated with a HP5526A.Further improvements in this measuring machine resulted in a range of 2 meters and a measurement uncertainty of about 5X10-8 meter by 1986.The document linked above describes in detail a list of sources of uncertainty in measurements and the researchers methods to minimize the uncertainty as well as calculating the individual contribution of these uncertainties.

In the world of metrology there is an orthodox method to identify and measure the individual sources of uncertainty in your measurement.This orthodox method basically provides a statistical description of how well you are able to make a measurement.It works by identifying and categorizing as many possible sources of error in your measurement, and calculating the effects of these sources of error across a range.

An example of what I mean is if there is an error in measuring the temperature of a length of metal, then there will be a resulting error in the calculation of how much length change of the object due to the changing temperature.However if the uncertainty of the temperature measurement is known, then the uncertainty of the length change can be calculated as well as the size of the overall length change.

Many sources error are identified and their effects on the measurement are estimated. The estimate is done using statistical methods.These uncertainties are then combined together to provide you with a number which describes your ability reliably make an accurate measurement.

I will use the NIST document as a basis to identify my sources of uncertainty for this project.  I will then use the same statisical methods to determine my final measurement uncertainty, when I am making measurements.