NBS Internal Report 80-1967; 24p. April 1980.
Angle block; autocollimator; calibration; flatness; intercomparison; random error; squareness; standard deviation; systematic error; uncertainty.
One service performed by the National bural of Standards is the calibration of angle blocks. Test blocks normally come in sets of 15 nominal sizes from 1" to 45°. Their angular values are calibrated by intercomparison with NBS master angle blocks and other test blocks of the same nominal size. Each test block is also measured for its maximum out-of-flatness and out-of-squareness. Statistical tests are performed in order to maintain control over the short-term and long-term variability of the measurement process.
A complete description of the measurement process is given with special attention paid to the mathematical model for the measurements and the least squares estimation of the angular values. The method for determining the standard deviations of the short-term and long-term errors is also given.