Apparatus for measuring enzyme concentrations using an optical instrument such as a spectrophotometer

Claim 2

Apparatus for measuring changes in absorbance per unit time, comprising: means for periodically comparing substantially monochromatic radiation transmitted through an absorbing sample substance to substantially monochromatic radiation transmitted through a standard substance, and for generating a series of digital signals, each said digital signal representing one said periodic comparison and comprising a pulse train having a length proportional to the logarithm of the ratio of the intensity of the radiation passing through the standard substance to the intensity of the radiation passing through the sample, said ratio being proportional to the absorbance of the sample substance at the time of said periodic comparison; counter means for comparing the number of pulses generated during any two consecutive time intervals, each said time interval comprehending at least one said digital signal, said counter means also for producing a signal representative of the change in said digital signals per unit time.

Claim 3

Apparatus in accordance with claim 1, wherein said counter means includes means for evaluation the summation of said pulses generated during a time interval and for determining the difference between said summation and a stored summation from an immediately preceding time interval.

Claim 4

Apparatus in accordance with claim 1, wherein said means to compare substantially monochromatic radiation includes a spectrophotometer.

Claim 5

Apparatus in accordance with claim 2 wherein said counter means includes an up/down counter for evaluating said summation of said digital signals during said time interval.

Claim 6

Apparatus in accordance with claim 2, wherein said counter means includes: a first counter for evaluating said summation of pulses generated during a preselected time interval; and a second counter for receiving said summation from said first counter determined during the immediately preceding time interval, for evaluating the summation of said digital signals during a current preselected time interval, and for determiNing the difference between said first counter summation and said second counter summation.

Claim 7

Apparatus in accordance with claim 1, wherein said counter means includes: a first counter for evaluating the summation of said pulses generated during a preselected time interval and for storing said summation; a second counter for receiving said summation of pulses stored in said first counter and for using said received summation as a base from which said second counter digitally counts backwards one count for each pulse generated during the next succeeding preselected time interval so as to determine the difference between the number of pulses generated during each of the two succeeding time intervals.

Claim 8

Apparatus in accordance with claim 1, including means to select the length of said preselected time interval so that the number of digital signals comprehended thereby may be varied.

Claim 9

Apparatus in accordance with claim 6, including means for maintaining a positive count in said second counter regardless of whether the optical density of the sample is increasing or decreasing towards the optical density of the standard.

Claim 10

Apparatus in accordance with claim 1 including: means to select the duration of said time interval; reading means for reading and displaying said change in said digital signals; and control means responsive to said means to select the duration of said interval for causing said reading means to display said change in said digital signal in terms of fixed units of time regardless of the length of the selected interval.

Claim 11

Apparatus in accordance with claim 9 wherein said control means includes: clock means to cause said means to compare substantially monochromatic radiation to generate a plurality of digital signals during said selected time interval; and said control means including means to vary the number of said digital signals stored and compared to maintain said change in said digital signals in terms of fixed units of time.

Claim 12

Apparatus for measuring changes in absorbance per unit time, comprising: means for periodically comparing substantially monochromatic radiation transmitted through an absorbing sample substance to substantially monochromatic radiation transmitted to a standard substance, and for generating a series of digital signals, each said digital signal representing one said periodic comparison and comprisisng a pulse train having a length proportional to the logarithm of the ratio of the intensity of the radiation passing through the standard substance to the intensity of the radiation passing through the sample, said ratio being proportional to the absorbance of the sample substance; first counter means for counting the number of pulses applied thereto during each of a plurality of successive preselected time intervals; second counter means for receiving said count at the end of each said preselected time interval and for evaluating the difference between said count and the number of pulses applied to said second counter means during the next succeeding preselected time interval; and means for applying selected digital signals to each said counter means during each said preselected time interval.

Claim 13

Apparatus for measuring changes in absorbance per unit time, comprising: means for periodically comparing substantially monochromatic radiation transmitted through an absorbing sample substance to substantially monochromatic radiation transmitted to a standard substance, and for generating a series of digital signals, each said digital signal representing one said periodic comparison and comprisisng a pulse train having a length proportional to the logarithm of the ratio of the intensity of the radiation passing through the standard substance to the intensity of the radiation passing through the sample, said ratio being proportional to the absorbance of the sample substance; first counter means for counting the number of pulses applied thereto during each of a plurality of successive preselected time intervals; second counter means for receiving said count at the end of each said preselected time interval and for evaluating the difference between said count and the number of pulses applied to said second counter means during the next succeeding preselected time interval; and means for applying selected digital signals to each said counter means during each said preselected time interval.

Claim 14

Apparatus in accordance with claim 11, wherein said second counter means uses said count as a base from which said second counter means digitally counts one count backwards for each pulse applied to said second counter means during said next succeeding preselected time interval.

Claim 15

Apparatus in accordance with claim 11, wherein said first and said second counter means each include an up/down counter.

Claim 16

Apparatus in accordance with claim 11, including means to select the length of said preselected time interval so that the number of digital signals comprehended thereby may be varied.

Claim 17

Apparatus in accordance with claim 11, wherein each said preselected time interval comprehends a plurality of said digital signals.

Claim 18

Apparatus in accordance with clAim 11, including means for maintaining a positive count in said second counter means regardless of whether the optical density of the sample is increasing or decreasing towards the optical density of the standard.

Claim 19

Apparatus in accordance with claim 11, including means for selecting which of said digital signals generated by said means for periodically comparing substantially monochromatic radiation are to be applied to said first and said second counter means.

Claim 20

Apparatus in accordance with claim 11 including: means to select the duration of said preselected time intervals; reading means for reading and displaying said difference evaluation; and control means responsive to said means to select the duration of said interval for causing said reading means to display said difference evaluation in terms of fixed units of time regardless of the length of the preselected interval.

Claim 21

Apparatus in accordance with claim 18 wherein said control means includes: clock means to cause said means to compare substantially monochromatic radiation to generate a plurality of digital signals during said preselected time interval; and said control means including means to vary the number of said digital signals stored and compared to maintain said change in said digital signals in terms of fixed units of time.