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 calibration plaque and envelope.
Unlock the instrument shoe. The spectrophotometer will ignore key presses if the shoe is closed. Notice that the word "CAL" is written between the first and second keys. To begin the calibration routine press both of these keys at the same time. The unit will then prompt "NO CALIBRATE YES".
Press the key beneath "YES". The spectrophotometer will briefly display its software version code, and continue by prompting "READ CAL WHITE"
Place the ceramic calibration standard on a firm, flat surface. Locate the spectrophotometer on the plaque. The crosshairs of the instrument shoe should cover the crosshairs printed on the calibration standard.
Hold down instrument for five readings on the white plaque until instrument displays "READING COMPLETE".
After releasing the instrument will either shortly display "CALIBRATION UPDATED" or ask for a black calibration by prompting "READ ZERO REFL.". If the instrument does NOT prompt for the zero reflectance calibration, it will return normal operation.
On occasion (or after a reset or aperture change) the unit will require a zero reflectance calibration. Ideally this calibration should be made in a darkened room. Usually it will work fine under a table. Hold the instrument with one hand at an angle to the floor and with the other hand close the shoe to activate the read switch. The hand should not cover the area of the target window. If the instrument sees too much light, it will display an error message "CALIBRATION FAILED". The procedure will need to be repeated in a darker environment.