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. It is packaged in the vinyl carrying case that came with the instrument. This item is the shoe-shaped plastic plate into which a ceramic disk is cemented.
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!
Unlock the instrument shoe and 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 patch on calibration reference ".
Place instrument into the shoe-shaped plastic plate and press down firmly. Do not allow the instrument to move until the message "< Completed >" is displayed on the bottom line.
Occasionally the instrument will also require a black or "zero reflectance" calibration. Should this be required proceed as follows:
Hold the instrument beneath a table or desk.
The instrument should be pointed towards the floor.
Squeeze the shoe closed and wait until the black calibration is concluded.
Generally speaking a black calibration is not required unless there has been a change of optics. A dirty optical system too can trigger this response. Should your densitometer not pass the black calibration - gently clean the optical path with dry compressed air. Do Not use a high-pressure air line: rather canned air as is used to clean fine camera lenses is appropriate. Repeat the entire calibration procedure from the top after the unit has been cleaned.