• Insert a cuvette containing the solution of lowest absorbance (usually water).
  • Press the CAL button.
  • The display will show either 100.0 (transmittance) or .000 (absorbance).

The calibration values are retained when the colorimeter switches off but it is a good idea to recalibrate fairly frequently. Calibration values may change if the ambient temperature changes so exposure to strong sunlight or other sources of heat should be avoided.

The colorimeter is sensitive to a change of 0.1% of the transmitted light.