Rate analysis system with overrange signal detection circuit for identifying false signals

Abstract

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.

Inventors

• 👤 T Woods
• 👤 R Ray

Bibliographic Details