Research On Measurement Technology Of CT Sensor Based On MEMS Technology

Seawater temperature and salinity are two of the most important factors in marine dynamic environment.The measurement of seawater temperature and salinity is of great significance to the development and utilization of marine resources and military defense.The future trend of intelligent and networked oceanic observation technology will make the oceanic sensor technology develop in the direction of miniaturization and low cost.The existing traditional conductivity and temperature sensors have the problems of high cost and high consistency in mass manufacturing,which restrict their wide application in mariculture,marine environmental monitoring and other fields.This topic starts from the measurement principle,through theoretical analysis and finite element simulation analysis,choose to use thin film platinum resistor as MEMS temperature sensor,ring plane four electrode conductivity cell as MEMS conductivity sensor.Based on the fluid-solid heat transfer function and the Joule heat effect,the influence of Joule heat on the temperature measurement of MEMS platinum resistance temperature sensor is simulated and analyzed.According to the simulation data,the distance between wires of platinum resistance temperature sensor is determined to be 250?m.Through the simulation analysis of electric field and potential distribution,the electrode structure and lead mode of the conductivity sensor probe are optimized.Finally,the probe design scheme of the MEMS based CT sensor is determined.After completing the processing,packaging and assembling of the probe,the corresponding signal acquisition system is designed according to the measurement characteristics and precision requirements of MEMS sensor.The overall control of the signal acquisition system is realized through the functional design of the system software.Finally,in order to verify the accuracy and repeatability of the MEMS based CT sensor,one calibration and three retest experiments were designed and carried out.Through the comparison and analysis of the experimental data and the standard instrument SBE49 CTD experimental data,the maximum drift of temperature is0.0068 ? as well as the maximum drift of conductivity is-0.0424 ms /cm of the MEMS based sensor after calibration about one month.The experimental results also show that the MEMS CT sensor has good data repeatability and stability,it meets the design requirements of the sensor technical specification.