Design Of Calibration And Verification System For CTD Measuring Instrument Based On Virtual Instrument

Oceanographic measurement is the foundation of the development of marine science.The basic property parameters,temperature,depth,salinity,corresponding temperature,pressure and conductivity are the basic measurements of sea water.At present,due to the limitation of cost and portability,as well as the aging of hardware and the impact of equipment,it is necessary to calibrate and calibrate the equipment regularly.In this paper,a calibration and verification system of temperature and salt depth measuring instrument based on virtual instrument is designed and implemented,which can simulate the change of marine environmental parameters by configuring digital potentiometer,and complete the functional verification of the system.After being calibrated by the standard equipment,the same seawater environment is measured with the temperature-salt depth measuring instrument(calibrated equipment),and the calibration work of the measuring instrument can be completed by the upper computer with the aid of curve fitting method.On the basis of studying the working principle of common temperature,pressure and conductivity sensors,the equivalent sensor(sensor measurement model)is designed,and the hardware circuit and software program of the system are designed according to the performance requirements of the system.Based on the theory of salinity and conductivity,the corresponding parameters are calculated,and the language G is chosen to complete the interface of double serial transmission in LabVIEW environment,so that the calibration parameters can be obtained.The device selection should be based on the principle of low drift,low noise and high precision,so I select TM4C1294 and ADS1262.According to the functional requirements of the system,the main control circuit based on TM4C1294,the measurement model of sensor,the A/D acquisition circuit based on ADS1262,the signal conditioning circuit,the communication circuit and the power supply circuit are designed.Data communication program After the hardware circuit is welded and adjusted with the software part,the calibration of the system is completed by means of contrast test with SBE 37-SI CTD,which is calibrated by standard equipment.Based on this standard,the calibration experiment of the existing CTD measuring instrument in laboratory is carried out in order to improve its measuring accuracy and accuracy,and to judge whether its verification result is up to standard or not.The result shows that the expected function of the system can be realized.