Research On The Spectrum Electrochemical Micro Current Detecting System

The Scanning Electrochemical Microscope which is so called the SECM is a new scanningprobe microscopy which is put forward by A. J. Bard at the end of the80s that makes up theshortcoming that the scanning tunneling microscope can’t provide the electrochemistryinformation. It applies the electrochemistry principle, drives the very little probe and scansbeside the sample to measure the electrochemistry current which is provided by the oxidationor deoxidation reaction in the microcell. The current which is collected and processed canreflect the disposition of the electrochemistry activity in the microcell as the form of thefigure and then can obtain the corresponding electrochemistry information in the microcell.At present, the highest resolution ratio is100nm and so it is applied widely in the area ofchemistry and biology. Because of the chemistry sensitivity of the SECM, it can not onlyresearch the geometry feature of the conductor and insulator, but also can distinguish theelectrochemistry activity of the surface of the nonuniform electrode and process the materialin the range of micron and so on.As the stability becomes worse as the sensitivity becomes higher in some of theinstruments, the article designs a Micro electric current signal detection circuitry afteranalyzing the requirement put forward by the micro electric current signal detected by theSECM and uses the high accuracy ADC to collect the weak current signal. It adjusts thecircuitry gain automatically and changes the value of the spectrograph wavelength real timewhich has the characteristics of high accuracy, practical circuitry, high reliable and so on, thatimproves the circuitry’s resistance interference.The major of the article is summarized as follow：(1) By reading lots of references, we introduce the state of the development, researchbackground and development potential for the SECM and make a conclusion to themeasurement technique of the modern microcurrent and apply it to the detection of the SECMmicrocurrent.(2) We introduce the basic operation principle, operating mode and component for theSECM and make a detail description about the choice, purpose and function of the threeelectrode electrochemistry sensors.(3) The design of the hardware circuit is the issue of this article. It concludes the choice ofthe light source, microcurrent detection circuit, signal collecting circuit, the design of thestored program control voltage and the AGC circuit.The current collection circuit is realizedby the use of the high resistance operational amplifier and the meter amplifier. It uses the highaccuracy ADC to collect current signal. This method can not only apply to the detection of themicrocurrent, but also can use in the occasion of collecting the weak signal.(4) The article describes how to control the detection circuitry by the use of the ports andhow to drive the serial port and how to develop the GPIO port of the embedded system. It gives the driving program and the flow chart of the application program and designs the PCterminal control software to realize the function of processing the data.The system uses the OK6410embedded system as the platform which combines themicrocurrent detection circuit, the weak signal collecting circuit, the automatic gain adjustcircuit and the spectrograph control port and it makes a curve-fitting to the collected signalthat makes the relation of the microcurrent, voltage and the wavelength spectrometer moreclearly in the SECM.