Watermelon Maturity Of Non-biological Information And Testing Equipment Development,

Recent years, with the improving of people's living standard, the demand for the quality of watermelon and muskmelon is also increasing. The development of transportation also promotes the consumption of watermelon. On the other hand, the majority of consumers are not able to correctly choose mature watermelons; even melon farmers may pick immature watermelons. At present, the price of maturity testers is very expensive; what's worse, they are not easy to carry. Most of the maturity testers are based on PC and used in research; this greatly limits the popularization and application of maturity testers. After analyzing the testing technology of existing watermelon maturity testers and domestic and foreign research status, this paper designs a portable watermelon maturity tester based on single chip computer, with the purpose of improving the portability of watermelon maturity tester and reducing the cost. This new type of maturity tester has the characteristics of easy to carry, i.e., there is only a small knocking device and a small instrument box. It not only can meet the requirements of melon farms while picking watermelons but also satisfy the purpose for consumers to choose watermelons. Compared with other watermelon maturity testers, the characteristics of this tester are: adopting sound signal processing to realize nondestructive examination, collecting the sound signals of the knocked watermelon, then use single chip to carry out digital signal process to the sound signals, combining the characteristic value of the sound of knocked watermelon, the maturity of watermelon will be measured. The whole testing process does not depend on PC but only feature extraction through PC in the feature extracting stage, this realizes the portability and also greatly reduces the cost.Non-biological information research of watermelon maturity tester and watermelon maturity are dealt with in this paper. The PCB design and software programming of testing instrument and the collecting of different maturity watermelons'knocked signals are finished.The hardware circuit mainly includes:①the generation device of signal and the measurement module of the radius of watermelon, this part mainly serves as the generation device of knocking sound signal; this parts serves as the generation device of knocked sound signals, and a free beam is fix in the device to measure the radius of watermelon;②sound signal adjustment module, which magnifies the voltage signal of weak knocking sound so as to ensure the effective signal not to be lost and the output signal is easy to be transformed by A/D converter, which ensures the scope of application conversion to the maximum extent and improves the conversion precision;③A/D module, which converts analog signal into digital signal that serves as the premise of digital signal processing;④level conversion module, which realizes the switch of TTL and RS-232;⑤external data memory module, which is used for the storage and read of digital signals;⑥single chip computer, which realizes the control and signal processing of the whole system;⑦display module , which displays relevant information such as start indication, wait state and final maturity display.The control software mainly includes:①A/D conversion program, that realizes the D/A conversion of 12 digit A/D converter;②serial communication program, that is used for the communication with PC and facilitates signal data analysis;③the storage and read of external data register and expands data memory;④FFT program in single chip, which carries out frequency spectrum analysis to signal and feature extraction within the frequency domain;⑤maturity calculation program, which calculates the maturity degree of the measured watermelon according its maturity characteristics;⑥display and output program, which is used to display relevant information.The feature extraction of watermelon knocking sound signal mainly includes:①PC accepting the data transmitted by single chip computer;②carrying out code conversion and relevant processing of data;③dealing with the signal and finds the characteristic value;④verifying the correctness of the characteristic value.The research of this paper lays a solid foundation for the development of portable maturity testers, so it has practical significance and application prosperity.