First steps.

At first I needed to know, if it is possible to make quantitative measurements with Arduino. For that purpose I decided to build a device similar to what I had it in mind at the beginning: a photoresistor connected to Arduino, a cuvette and a calibration curve made of colored solutions with different concentrations.

In order to collect data, I used the program- PLX-DAQ. It transferes data directly to MS Excel in real-time (apart from MS Excel all programs that I used to work with Arduino are avaliable on the Internet for free).

I tested that “device” with KMnO₄- and Malachite green- solutions in different concentrations, different light intensity and LED-color. Measurements show that a pretty precise correlation –the correlation coefficient R² was always between 0,9961 and 0,9977- really exists and it is possible to use such a simple “device” as a turbidimeter (or something similar). Here I need to notice, that the exact placement of the cuvette is very important, a difference in one millimeter can result in big difference in the measurements; also it is necessary to exclude the influence of external light- I used a box and a measure cell made of cardboard: