The Design Of Coulostatic Corrosion Monitor Based On USB Interface

In industrialized countries, the economic loss caused by metal corrosion is 3% -5% of GNP. And successful corrosion monitoring will bring economic benefits dozens or even hundreds of times of the investment cost. So the corrosion Monitoring is considered to be an important means to guarantee production civilization.Most of the metal corrosion is electrochemical corrosion in actual project. Based on analysis and comparison with various detection methods for electrochemical corrosion, we can know that coulostatic detection is a method with advantages of simple to carry out, fast, sensitive, non-destructive and generally suitable condition. In order to achieve automated measurement of coulostatic corrosion monitoring, this subject research a coulostatic monitoring instrument based on USB interface. Host control coulostatic module through USB bus loading excitation signal to polarize electrode, at the same time, collecting polarization potential to the host automatically. And the host software has the functions including data smoothing, software filtering, curve fitting, display, print, save and so on.The main researches of this thesis are as follows:1. Analyze the advantage of coulostatic method by comparing polarization curves, AC impedance and other electrochemical detection methods. Electrochemical parameters are derived from the theory of equivalent circuit based on the theoretical analysis of coulostatic method. Analyze four equivalent models and derive the response equations under a constant power excitation through Laplace transform and its inverse transform.2. Complete the designs of Coulostatic module and Coulostatic interface module. Using capacitors charge and discharge to load excitation signal, which by reducing charging capacitor Cs and increasing the charge voltage Vs to reduce the time constant RsCs makes charging speed more than 3 times faster. Using CY7C68013 produced from Cypress Company as the interface chip with endpoint FIFO interface FIFO combined, greatly enhance the USB2.0 bandwidth and realize high-speed data acquisition.3. Complete the designs of firmware in interface chip, USB device drivers and host monitoring software. Monitoring software applies MATLAB and VC mixed programming, combining the friendly interface of VC and the powerful numerical computing power of MATLAB. Beside anti-interference measures in hardware, the system also provides software to eliminate noise. Firstly apply data smoothing by method of five point three times smoothing, and then low-pass filter to remove 50HZ of electricity and high frequency interference, which ensure convergence and accuracy of the collected data.