Accurate measurement of algae concentration is important for prevention and treatment of algal bloom, which may seriously affect the fishery production and residents' health and safety.Measurement of chlorophyll a concentration using chlorophyll fluorescence is an effective means to reflect the algae concentration.The fluorescence is very weak and is susceptible to ambient light, so a lock-in amplifier was employed to measure the fluorescence.LED was used as excitation light source, PIN detector was employed for fluorescence detection, and a lock-in amplifier was designed based on AD630.Anabaena of 10 concentration gradients between 0-100 μg/L was used for system testing, and the measurement results showed that the correlation coefficient of the measured value and the actual concentration of chlorophyll a is 0.99815.%藻浓度的准确测量对于防治水华爆发,进而保障渔业正常生产及居民健康安全具有重要作用.通过叶绿素荧光测量藻类叶绿素浓度是反映藻浓度的有效手段.针对叶绿素a荧光非常微弱,且易受到环境光干扰的问题,采用锁相放大技术进行叶绿素a荧光测量.采用LED作为激发光源,以PIN光电二极管为探测器,并基于AD630设计了锁相放大电路.采用0~100 μg/L浓度范围内10个浓度梯度的鱼腥藻样品进行测试,结果表明测量值与实际叶绿素a浓度的相关系数达到0.99815.
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