This arrangement was designed to improvement signal measurement and to attain this subject the needful electronic network for signal generation and conditioning was also provided and its diagram is depicted in Fig. 2.
The phototransistors (Det1, Det2) and the operational amplifiers (OA1, OA2) were assembled to form two signals transducers network where light coming from LED was converted to difference of potential. The response of each network
presented linear relationships between light absorption and the concentration of the chemical specie inside of the flow cell.
The network comprising the operational amplifier OA3 was configured as an analog signal summing, therefore,
the potential difference presented in its output (pin 6) was proportional to the addition of the signals coming from the operational amplifiers