| Optical fiber sensors are widely used in many fields such as industry,power,medical treatment,transportation and so on,due to its unique sensing mechanism and characteristics.In the extreme environment of high magnetic field,high voltage,high temperature,high pressure,high salinity and long distance,the measured parameters are transformed into the changes of intensity,wavelength and phase of light by using the transmission,refraction and dispersion effects of light.Through optical fiber transmission,photoelectric conversion senses the measured characteristics and forms an optical fiber sensing system,which can effectively solve the problems of accurate detection,fault diagnosis and dynamic sense of the characteristics of the measurements.As a necessary resource for human production and life,water quality directly affects the quality of factory products and human health.Turbidity is one of the important indicators in water quality detection.Its effective measurement is of great significance to the discharge of industrial wastewater,the qualified detection of industrial water and domestic water.Turbidity detection can be carried out by manual sampling,which has the disadvantage of low efficiency.It can't be adapted to industrial applications that require real-time online turbidity collection,multi-node monitoring and harsh environment.Therefore,it is necessary to design an optical fiber turbidity testing system to support the above application occasions,to ensure the continuity and stability of measurement,to solve the real-time problem of turbidity monitoring in industrial production process,and the environmental stability problem of the testing system.The optical fiber turbidity measurement system belongs to the typical fiber optic intensity modulation system.The electrical part of the traditional system is usually constructed by discrete analog devices.This paper combines the IoT technology to design a full digital optical fiber turbidity measurement system,which has the characteristics of high real-time,high adaptability,full integration and full digital.The system is composed of digital optical fiber turbidity acquisition unit node and digital monitoring center.Digital optical fiber turbidity acquisition unit node picks up transmitted light intensity,reflects the value of turbidity according to optical effect,compares with setting threshold,controls relay action,and transmits it to the system data center via WiFi,which is convenient for monitoring,recording and controlling.The electrical part of the digital optical fiber turbidity acquisition unit node is designed in full digital way.The unit uses RL78/G14 as the main control unit,infrared proximity sensor as IR LED driver and photoelectric conversion output unit,ESP8266 as wireless transmission unit,with other peripheral circuits and software to complete human-computer interaction,turbidity data acquisition,display,threshold action and WiFi transmission functions.The unit can also be used for the calibration of turbidity measurement curve.Each digital optical fiber turbidity acquisition unit node completes data interaction with the digital monitoring center under the framework of MQTT communication.This design has set up six nodes of optical fiber turbidity acquisition unit,of which MQTT server is built on Alibaba Cloud.SK-S7G2 is chosen as the hardware development platform and GT202 Kit as the WiFi communication unit in the digital monitoring center.The platform runs ThreadX operating system,completes data interaction and human-computer interaction with turbidity collection nodes through graphical interface configuration and software programming.This paper first introduces the research status at domestic and overseas and the principle of turbidity measurement,then describes the overall structure of the system,next describes the software and hardware of each unit in detail,finally uses standard turbidity liquid to calibrate the system,tests each unit,and then carries out the overall test of the system,and summarizes and prospects the research. |
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