Abstract A rate analysis instrumentation system is disclosed including a sample cell and detection means for producing an electrical cell signal proportional to a parameter of a sample reacting within the cell. In a preferred embodiment the parameter comprises the enzyme activity of a sample, measured by the light absorbance characteristics of the sample. Electrical means are provided for differentiating the electrical cell signal to obtain a rate signal, and display means are provided for displaying the rate signal or a value determined therefrom, such as enzyme activity or concentration. A constant rate detection circuit is provided to permit measurement of the rate signal only during periods when the reaction rate and the cell signal are linear. The constant rate detection circuit includes electrical means for differentiating the rate signal to derive a second derivative of the cell signal, and comparing the second derivative signal to a threshold value to determine when the second derivative signal approaches zero. Since a zero second derivative signal indicates that the rate signal is constant and the cell signal is linear, the second derivative signal is used to initiate a predetermined operation of measurement and display means in the instrument. An overrange protection circuit is also disclosed for excluding false rate signals, such as signals having characteristics that fail to meet predetermined acceptable limits. The overrange protection circuit includes means for comparing the rate signal with predetermined upper or lower amplitude limits, as well as with a total deviation limit. An overrange signal and a blank signal are produced upon departure of the rate signal from any of the predetermined limits, which signals control the measurement and display means.
A rate analysis instrumentation system including electrical first derivative circuit means, adapted to receive an electrical sample signal to be rate analyzed, for producing an electrical rate signal therefrom, display means associated with said first derivative circuit for selectively displaying a value proportional to said rate signal, overrange detection circuit means responsive to said sample signal for identifying unacceptable characteristics of said sample signal, and overrange logic circuit means responsive to said detection circuit for producIng a blank signal to inhibit the display upon the occurrence an unacceptable sample signal.
Claim 2
Dependent Claim
90 words
A rate analysis instrumentation system including electrical first derivative circuit means, adapted to receive an electrical sample signal to be rate analyzed, for producing an electrical rate signal therefrom, display means associated with said first derivative circuit for selectively displaying a value proportional to said rate signal, overrange detection circuit means responsive to said sample signal for identifying unacceptable characteristics of said sample signal, and overrange logic circuit means responsive to said detection circuit for producIng a blank signal to inhibit the display upon the occurrence an unacceptable sample signal.
Claim 3
Dependent Claim
57 words
The rate analysis instrumentation system of claim 1 wherein said overrange detection circuit means includes at least a first comparator responsive to said sample signal for identifying when the sample signal exhibits an unacceptable total change in value over a predetermined interval, and second comparator circuit means for identifying when said sample signal reaches an unacceptable level.
Claim 4
Dependent Claim
56 words
The rate analysis instrumentation system of claim 2 wherein said overrange logic circuit means includes at least one AND gate means, adapted to be enabled by a time delay signal for passing the output of said logic circuit means only at a predetermined time delay interval after the sample signal is received by the instrumentation system.
Claim 5
Dependent Claim
50 words
The rate analysis instrumentation system of claim 3 wherein said overrange logic circuit means further includes selection circuit means for selecting whether said second comparator circuit is responsive to a sample signal level above the starting level of said sample signal or below the starting level of said sample signal.
Claim 6
Dependent Claim
34 words
The rate analysis instrumentation system of claim 4 wherein said overrange detection circuit means further includes third comparator means responsive to the rate signal for determining when the rate signal exhibits an unacceptable level.