All instruments require periodic calibration to ensure accurate data. If new to calibration, 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 reflection standard. This item is a black, brick-shaped, plastic box; a ceramic disk is cemented on the surface near one end, and a thumb-sized hole is drilled near the other end. By squeezing two plastic clips it is possible to open the box. This enables cleaning of the dispersion cone located beneath the hole. Take care to clean the cone gently. Scratches will adversely affect your black calibration measurements.
Turn the standard over and note the paper decal attached to the bottom surface. This item is a serialized part. Each is individually certified and the numbers printed on the decal are traceable to the National Institute of Standards and Technology. Note also that the instrument's serial number is penned in at the bottom of the decal. Ensure that this number matches that of the instrument which is being calibrated! Failure to observe this will result in a poorly calibrated instrument!
Wake the instrument and then press the 'x'(Exit) key to access the main menu.
Press the 'DOWN' key until the prompt "Calibration" is highlighted: then press 'ENTER'.
The instrument will immediately prompt "<Measure White Ref >".
Place instrument into the shoe-shaped plastic plate and press down firmly. Do not allow the instrument to move until the message "< Success! >" is displayed on the instrument.
The instrument will next prompt "<Measure Black Ref >".
Turn the instrument locating the aperture over the hole. As before, press down firmly. Do not allow the instrument to move until the message "< Success! >" is displayed on the instrument.