106 2 Installation and Specifications
2.3 Software setup
Nonlinear error correction (NLEC)
NLEC minimizes or eliminates the small inaccuracies in the X-Y 
measurement plane due to machine irregularities and encoder 
nonlinearity. Error correction coefficients are obtained by measuring a 
certified calibration grid. The actual values are then compared to the 
nominal grid values by the ND 1200. This comparison results in a final 
NLEC.txt file that contains the error corrections for all measured grid 
locations. When NLEC is enabled, the corrections are applied across 
the measured area of the X-Y measurement plane. To apply NLEC to 
a measurement plane:
U Verify that the crosshair probe is selected. Press the PROBE soft 
key to select it if necessary.
U Verify that the appropriate encoder reference marks are selected in 
the Encoders setup screen (See "Encoders screen" on page 92).
U Verify that the Startup zero field of the Measure setup screen is set 
to YES (See "Measure screen" on page 112).
U Cycle the ND 1200 power off and then back on the establish the 
machine zero if necessary.
U Press MENU/SETUP to display the setup menu and then highlight 
the Scale Factor menu item.
U Verify that the Active choice field specifies NO.
U Press MENU/CLEAR/CLR ALL to clear all existing datums, part 
alignments and part data. 
U Press MENU/SETUP to display the setup menu and then highlight 
the LEC menu item.
U Verify that all Standard and Observed data fields contain the value: 
1.000 to eliminate the possibility that a previous LEC correction will 
influence this NLEC correction.
Reference marks, or a manual reference position must be 
recognized by the ND 1200 upon startup to create a 
repeatable machine zero. Machine zero is required for 
NLEC error correction.
When scale factors are used, they must be applied after 
error corrections.