Photometer for digital indication of concentration

Claim 1

A photometer for the digital display of the concentration Conc. St of a test sample with respect to a standard solution in accordance with the formula Conc. St EA X F X 1/ESt where EA is the extinction of the test sample, F is a concentration determining factor and ESt is the extinction of a standard solution comprising: a signal generating means providing a time period proportional to EA X F; a base frequency oscillator; an electrically adjustable frequency divider coupled to said base oscillator for providing an adjustable frequency pulse signal; a coincidence gating means, said adjustable frequency divider and said signal generating means being connected to inputs of said gating means for providing adjustable frequency pulses at the output thereof during the time period; digital counting means coupled to the output of said gating means and operable by said adjustable frequency pulses for totalizing and recording the pulses received during the time period proportional to EA X F; and an adjustable storage means for receiving and storing an electrical indication of ESt, said means being coupled to said adjustable frequency divider for electrically altering the frequency of the adjustable frequency pulse signal and the provision of pulses to said digital counting means in accordance with the stored indication of ESt to provide a digital counting means recording corresponding to 1/ESt EA X F and the test solution concentration Conc St. with respect to a standard solution.