These parameters are relevant only if an analog output card is installed in the support unit. The channel centers represent the target values for product color and height. The values entered here for channels 1-3 (RGB, XYZ, L*a*b*, or Lab) will probably be the same as those entered for the Target Values parameter if the product standard values were used as the target values. If hitching standard values were used as the target values, the center values may or may not match the target value. If DIFFERENCE was chosen as the data mode, the channel centers will automatically default to zero to indicate that, ideally, there is no difference between the product standard and the sample. The value entered for channel 4 will be your expected product height.
The channel spans should be based on the product tolerance band (NOT the threshold) around the target values. You may even want to allow a small margin outside the tolerance band so that you can continue to examine the values even if they are slightly outside the tolerances. The number you enter in the hand-held or fixed terminal should actually be half of the total span, since the entire span range is symmetrical around the target values. For instance, if 0 - 100 (L) is the desired range and your target value is 50, you would enter 50 as the center and 50 as the span.
If additional assistance is required, you may contact HunterLab.