Abstract: An instrument kit includes a photometric instrument and a standardizing ampoule. The standardizing ampoule includes a machine readable code that is recognized by the instrument when the ampoule is inserted to initiate a standardizing routine. An analysis kit includes an optical filter assembly and a sample ampoule to be used with the instrument. The filter assembly also includes a machine readable code that is detected by the instrument when inserted to identify the particular test to be conducted by the instrument. The instrument automatically applies the relationship between detected light and concentration of a substance for the particular test and displays the sample concentration in numeric digital form. The instrument operates automatically, and there are no buttons or other external input devices.