A water analyzer, based on a photoelectric sensor, has designed, built and tested. It is designed to record automatically the optical density of some constituents in water. Laboratory tests have proved the instrument is sensitive to detect small changes in color of water. Generally, these constituents can be either measured by the bulky and costly analytical instruments like HPLC, or by the traditional methods of chemical analysis. The authors of the present paper have attempted to design an inexpensive, portable instrument using microcontroller. The instrument is designed using different colored LEDs and photodiode. The LED and the PWM circuit have been designed to produce a stable and intense source of light. An operational amplifier based current to voltage convertor is connected in series with the photodiode to convert transmitted light into analog voltage. Conversion of analog voltage to digital data has done by I2C type ADC. The data from ADC has fed to AT89C51 microcontroller for further processing of optical density, its calibration and display on character LCD. The developed device is light in weight, portable and economical.
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