4. Calibration
The 948 & 968 should be calibrated to the X-Rite standard the first thing each day
and every four hours of operation thereafter. However, a "NEED CALIBRATION"
message will appear in the display:
•If the calibration procedure has not been performed for 24 hours.
•If there is a 10°C change in temperature since the last calibration.
•If zero reflectance is measured improperly.
•If the lamp output changes.
Whenever this message appears the calibration procedure should be performed
before another measurement is taken to ensure accuracy.
Important Calibration Notes
• If you change apertures you must change the aperture setting, read zero
reflectance, & calibrate the unit (see Section 4.2, steps 1, 2, & 5a thru 5d).
• Dirt or dust in the optics area will cause an inaccurate calibration reading.
Refer to Section 8.2 for the optics cleaning procedure.
• The ceramic Reflection Standard is dramatically affected by smudge
marks, dust, and finger prints. The standard should be cleaned using a mild
soap and warm water solution, thoroughly rinsed with warm water, and wiped
dry with a lint free cloth. You must let the standard dry completely before
taking a calibration reading.
• If you are having linearity problems it’s possible that there is dust in the
optics or Zero Reflectance has drifted. If you improperly measure Zero
Reflectance the unit can not automatically detect the drift. If you suspect this
is the case, you should manually activate Read Zero Reflectance by
performing Steps 1, 2, & 5 of Section 4.2.
• Do not move the 948/968 while taking a calibration measurement. If motion
is detected an error message will be displayed and calibration aborted.
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