For reliable measurements, you must calibrate the spectrophotometer before measuring. You cannot continue with the measurement if you cannot calibrate the spectrophotometer successfully.

1. Place the spectrophotometer in its cradle, and then press the button on the spectrophotometer or click Calibrate on the screen.
2. If calibration fails, make sure the white tile on the cradle is uncovered and the white tile and instrument aperture are clean, and then repeat the calibration.