OPTISK DETEKTOR TIL FOTOMETRISK INSTRUMENT

摘要

An optical detector circuit for a photometric instrument for providing a high precision, low cost A/D conversion of a detected optical signal. A sampled signal is integrated in a sample signal integrator while a reference signal integrator is integrated in a reference signal integrator. Using dual slope techniques, the integrated reference signal is provided as an input signal to the sample signal integrator during a de-integration cycle to provide a ratio of the detected signal to the reference signal, useful in nephelometers. An inverted blanking signal may also be integrated in the sample integrator prior to an integration of the sample signal to improve the accuracy of the dual slope integration. The period of integration is selected as a multiple of the primary sources of interfering noise such as power line and flourescent light frequencies.