968 Spectrophotometer Operation Manual ***discontinued ... - X-Rite

3.5 Difference MeasurementThe 948 and 968 can measure the difference between a sample color and areference. In order to measure these differences the reference must first be enteredinto memory. There are 24 different locations to store references.The reference can be entered numerically using the key pad, or by measuring thereference color.> The ∆Whiteness and ∆Yellowness reference color can only be entered by measurement.Reference (Measurement)Measured references are stored spectrally and the tristimulus values arerecalculated each time a different illum/obs is selected. As long as references aremeasured, the instrument can automatically convert the spectral data to allow forviewing of difference measurements under various illum/obs sets.Reference (Numeric)Numerically entered references are saved with the selected illum/obs. A total of 7sets of numerically entered tristimulus values (with different illum/obs) can bestored in each reference location.If a different illum/obs is selected and no numerically entered reference supportsthat illum/obs, the instrument will turn "OFF" that reference location.The instrument can not recalculate to a different illum/obs if it was not previouslyentered during numeric reference entry.Operation ModeThe instrument can be set to operate in an automatic mode, where it willautomatically select the closest reference; or in manual mode, where you have tomanually select the reference locations you want to use. Refer to Section 5.2,Setting Operation Parameters for information on selecting manual or automaticreference operation.In automatic mode, the instrument will select the reference that is closest to themeasured color. If by some chance it is not the correct reference, simply press the[ILLUM] key twice and the unit will select the next closest reference.In manual mode, you mustmanually select the reference.Once you have selected areference, that reference will beused until you select a differentreference.To activate the Differencemode, press [DIF] and the ∆ signwill appear in the display. The∆Functions will have a "+" signin front of them for positivevalues instead of being impliedas in the absolute function.> ∆L*a*b*, ∆L*u*v*, & ∆L*C*H* show ∆E in function location.13DELTA SIGNX Y Z X + 4 . 1 2Y + 2 . 8 7 Z + 2 . 4 1C 2X Y ZX 4 . 1 2Y 2 . 8 7 Z 2 . 4 1FUNCTION ILLUM DIFCALPRESS TO TOGGLE DIFFERENCE(DELTA) ON & OFFPLUS SIGNDELTA ONDELTA OFF