A Fruit Citric Acid Concentration Detector for Fruit Farm IoT Applications

In this work, a fruit citric acid concentration detector for fruit farm Internet of Things (IoT) applications is newly proposed. The proposed detector composes of a citric acid sensor and a converter, including the analog processing circuits and a three-order continuous-time incremental sigma-delta modulator (CT-ISDM). Different to previous researches, the proposed detector is newly to overcome a serious problem of low-frequency noise arising from farming machines used in the fruit farm, such as agricultural vehicles. Moreover, the proposed detector has a high 14-bit system resolution. With these two advantages, through the digital output of the proposed detector, the information of fruit citric acid concentrations could be clearly obtained and easily transmitted by the IoT devices. The measured citric acid concentrations were 1.1–15.9 (g/mL), and the measured corresponding signal-to-noise-distortion ratio (SNDR) was 72.6–80.3 dB. As a result, the proposed detector can thus convert the citric acid concentrations into the SNDR linearly. Finally, an experiment to verify the proposed detector used in the fruit farm was also successfully validated. By measured and experimented results, the proposed fruit citric acid concentration detector was able to function normally for fruit farm IoT applications.