An In-Situ Highly Sensitive and Reliable Chlorophyll Sensor Based on Pseudo-Random Sequence Modulation

A highly sensitive and reliable chlorophyll sensor is proposed and evaluated to meet the demand of in-situ chlorophyll detection. As the major innovation, pseudo-random sequence modulation is introduced into the amplitude measurement of the fluorescence for the first time. Compared with the conventional single frequency square wave modulation, the pseudo-random sequence modulation could spread the spectrum of the fluorescence, and improve the sensitivity and the interference suppression ability of the sensor without increasing the complexity of the system' s hardware. The sensitivity experiments show that the sensor could detect chlorophyll as low as 0. 0103 g/ L, with the concentration range of 0–25 g/ L and the R-square of 0. 9998. In the interference suppression test, for the same interference in the passing band, the maximum response of the 31 bits PRS modulation system is 2. 3 times smaller than that of the single frequency square wave modulation system.