Geometrical testing of X, Y plotters

The statistical accuracy of plotters is determined by drawing a grid and then remeasuring it. If the plotting area is rectangular 40 grid points are used, if square, 25. Errors due to instability in the material on which the grid is drawn, and errors in the control measurements are eliminated. The accuracy of the plotter is determined, along with the two systematic errors, lack of orthogonality, and difference in scale between the axes, as well as the point standard error which is a measure of the magnitude of random errors. The method is described in detail both in theory and by means of an example.