Fig. 4. Relationship between the measured color ratio and the chlorine concentration.
between the two ROIs and it is inside the blue rectangular area. Similarly, its purpose is to collect the image data in red, green, and blue color planes for the solution under investigation.
4.2. Calibration and test
For chlorine solutions with different 13 concentrations in Fig. 2, the relationship between the calculated CR and the chlorine concentration is shown in Fig. 4. In this case, we find that a fifth-order polynomial of
86.008x5 +359.04x4 + 556.14x3− 402.96x2 +135.15x −15.804
is mathematically fitted very well (i.e., R2 =99.76%) with our
experimental data in the 0–1.0 ppm chlorine concentration range. This fifth-order polynomial function is then stored in our smart mobile phone for real time analysis.