Development of a Plural Colorimeter Module for Urinalysis Strip Readers

An optic module system is developed adopting multiple colorimetry units for the measurement of multi-pad urinalysis dipsticks. Multiple photometry system instead of moving mechanisms has the advantages of system reliability and simplicity as well as economic aspects due to the recent development of economic color light emitting diodes and stable photo sensors. An integration amplifier with programmable integration time, a current source circuit with selectable and stable current settings were connected through analog multiplexers to forty light emitting diodes for illumination and twelve photo transistors for reading each strip pad. All the circuits are controlled by a microprocessor through a simple set of serial communication commands. The detectability is eighteen times better than the minimum color difference of the test grading which is 0.013 in urobilinogen in the color space defined in this paper.