Ristandi, Thomas Ferry2021-08-232021-08-232020-09wahyu sari yenihttps://repository.unri.ac.id/handle/123456789/10105research has been conducted to Design of Fry Counters based on Optocoupler Sensor with Photodiode Analog Voltage Characterization. The fry counter uses an optocoupler sensor, namely an infrared LED as a transmitter sensor and a photodiode as a receiver sensor. The research began with designing the sensor holder, electronic circuits and software, characterizing the sensors, and statistical testing of fish fry counting. Characterization is carried out based on the measurement of the photodiode analog voltage by varying the photodiode resistance from 1 kΩ to 30 kΩ. Measurement of sensor characterization was carried out with four treatment conditions, namely: without water, with still water, with running water and running water with fish. Based on the characterization that has been done, it shows that the value of the photodiode analog voltage (Vp) decreases exponentially as the resistance value of the photodiode increases. The best photodiode resistance in terms of sensitivity and accuracy is in the range of 1 kΩ to 10 kΩ, this can be seen from the results of the sensor characterization where the resistance is above 10 kΩ the photodiode voltage when the sensor is passed by the fry almost coincides with the three previous condition treatments. Statistical testing with 100 fry samples in the photodiode resistance range of 1 kΩ to 10 kΩ obtained an average error percentage of 1% to 1.6%.enFry counteroptocoupler sensorinfraredphotodiodesensor characterizationArticle