Regular calibration is necessary to assure the accuracy of the color measurements. If you are new to this process it will help to use the AC adapter while following this series of instructions. The microprocessor will "sleep" if too much time passes between keystrokes.
Locate the black and white calibration plaques.
Remove the nose cover on the bottom of the MA instrument.
Press the left key under "MENU" (Note: if you see the word "READ" above the left key then double-click this key to exit the read mode) until "MENU PAGE 2" is displayed.
Next press the second key from the left under the word "CAL".
The spectrophotometer will briefly display its software version code, and continue by prompting "READ WHITE CALIBRATION PLAQUE exit zero cal".
Place the white calibration standard on a firm, flat surface. Locate the spectrophotometer on the plaque, so that the notches on the holder align with the notches on the front and left side of the instrument.
Hold down instrument for four readings on the white plaque until instrument displays "READING COMPLETE". After releasing the instrument will either display "LONG CALIBRATION UPDATED" or will ask for a black calibration by prompting "READ ZERO REFLECTANCE exit read".
If the instrument doesn't prompt for the zero reflectance calibration, it will return to normal operation.
Occasionally (about once a week or following a firmware reset) the unit will require the zero reflectance calibration. Align the instrument as described above on the black plaque, push the instrument down firmly and activate the reading by pressing the right key under "read".