Development Of A Small Dew Point Meter Capable Of Remote Data Transmission

This article aims to design a small dew point meter that can transmit data remotely for laboratory teaching,and can also be used in other fields where the dew point needs to be measured.This article summarizes the current research status of dew point meter and wireless communication technology,as well as the application of wireless communication technology in dew point meter.We find that the dew point meter developed so far has some problems and shortcomings such as:short data transmission distance,large instrument,high price and high power consumption,etc.To deal with these problems,this article proposes an design scheme for remotely transmitting dew point instrument.Including microcontroller,condensation detection,temperature measurement,humidity measurement,display module,and communication modules.the function of the dew point meter is realized through the high coordination of hardware design and software design.The hardware design is to design the circuit and build the hardware connection of each module,including the microcontroller,heating-cooling device and data acquisition part.After comparing the advantages and disadvantages of different microcontrollers,this article chooses the ARM chip as the microcontroller.Design and manufacture heating-cooling devices,use hot water and ice to achieve heating and cooling functions.The condensation detection design is based on the sudden change in resistance of the resistance electrode plate when it encounters water;this abrupt signal is collected by ADC as a "switch" for dew point temperature capture.Use temperature sensor DS18B20 and humidity sensor DHT11 to collect ambient temperature and ambient humidity.Use TFT-LCD touch screen for lower computer display.The feasibility of each module is verified through experiments.The software design is to compile the code and build the software connection of each module,including the software development environment,the main program and the driver code of each module.Based on C language,this aeticle completes the compilation of ADC driver code,temperature sensor driver code,humidity sensor driver code and display driver code from three aspects:working principle,timing operation and code writing.Calls each driver code to design the main program of the dew point meter,realizes the dew point temperature judgment,data acquisition and display,and the design of the interface of the lower computer.The communication design includes serial communication,LORA,Bluetooth and WIFI,which realizes four communication modes of the dew point meter.The design of four communication methods is completed from the three aspects of hardware connection,code compilation and host computer software.Communication functions can be selected and configured through buttons and touch screen operations,It can communicate at short distances or remotely,and can communicate to a computer or a mobile phone.Finally this article builds an experimental platform,tests the performance and communication effect of the dew point meter,including the response speed,accuracy and communication distance.By comparing the experimental value and the theoretical calculation value,it shows that although the accuracy of the dew point meter is slightly worse,it has fast response speed,good stability,small size and low power consumption,meets the needs of experimental teaching equipment usage scenarios.All four communication methods can be used for communication.Communication distance:LORA(900 m)>WIFI(19.21 m)>Bluetooth(15.48 m)>Serial port,and the suitable communication method is selected according to the principles of communication distance,safety,stability,and requirements for the upper computer.