Distributed Monitoring System Of Phosphine In Tobacco Warehouse Based On NB-IoT

The tobacco industry usually uses phosphine gas to kill insects,but the gas is unevenly distributed in large warehouses.Therefore,it is necessary to measure the gas concentration by a multi-point distributed monitoring device to evaluate whether the tablet input is qualified.This paper introduces a complete system for remote multi-point measurement of phosphine gas concentration,temperature and humidity.The system includes monitors,servers and client software.The monitor mainly includes three parts: measurement,control and communication circuit.The server and client software are mainly composed of device communication interaction,database and web page.The workflow of the system is as follows.At first,the measuring circuit converts the sensor output into a measurable voltage range,which is obtained by the control circuit and then packaged into a customized data format.Secondly,the package is sent to the server through a narrowband Internet of Things(NB-IoT)communication circuit.At the third step,the server analysis the data and sends them to the database for management.Finally,corresponding data and results are available for users through the web page.This topic studies the advantages and disadvantages of various Internet of Things networking,and eventually selects the communication method of NB-IoT,with advantages of long signal transmission distance,wide coverage,stable network and low power consumption.Meanwhile,a special data transmission protocol is designed for small amount of data,providing terminal packaging and server analysis with convenience.During testing,there are still problems such as unsmooth network.Hence,the method of terminal cache is adopted to effectively optimizes the packet loss rate.In addition,in the monitor circuit design,several improved measures to reduce power consumption are involved in the design to minimize the power consumption of the monitor and maximize the battery life.