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The precision of displayed readings depends on the units you choose. For example, readings in degrees are
displayed to three decimal places. However, that doesn’t mean that the readings are accurate to 1/1000ths of a
degree. In general, you can’t assume th
at readings are accurate to all displayed decimal places. For information on
the accuracy of the readings,
see “
•
Polar
Magnitude
and
Direction
indicate the angle of inclination in the direction of maximum inclination. In the
figure below, the highest point on the edge of the wafer is indicated by the arrow,
Direction
is the angle the
arrow makes with the x-axis, and
Magnitude
is the angle between the wafer and the horizontal (or reference)
plane. Direction is measured counter-clockwise from the x-axis and is always positive.
Magnitude
is also
always positive.
Display Units for Horizontal Inclination
Horizontal inclination angles can be displayed in degrees or milliradians (mradians), or as rise over run. Rise over
run is the vertical height of a point on the edge of the wafer relative to the center of the wafer (rise over radius) or
relative to a point on the opposite edge (rise over diameter), as shown below.
Rise over Radius
Rise over Diameter
In addition to choosing whether to display the measured rise over the radius or diameter of the wafer, you can also
choose to display the value in either inches or millimeters:
•
mm/r
Millimeters of rise over the radius.
•
in/r
Thousandths of an inch of rise over the radius.
•
mm/d
Millimeters of rise over the diameter.
•
in/d
Thousandths of an inch of rise over the diameter.
