Circuit Design Of Micro-current Signal Detection Of Gas Sensor

The micro-current signal detection instrument designed in this paper is based on the application of weak signal detection technology in semiconductor gas sensors.In the research of semiconductor gas sensor materials,the internal resistance of some sensors can be as high as G?,and the current signal will be as low as pA.This type of signal detection is called as the detection of very weak micro-current signals.The signal-to-noise ratio of the signal is extremely low,making detection difficult.Some traditional micro-current detection instruments are expensive and bulky,and occupy large space.With the increasingly application of micro-current detection,a micro-current detection instrument with small size,light weight and low cost is expected,which can cater to the realistic needs and realize its application value.Therefore,the main content of this article is to design and produce a micro-current detection instrument,which can complete the detection of the signal of the large resistance type gas sensor,and can also detect the input current signal.The main body of the paper is summarized into the following parts.First,a review of micro-current detection methods is introduced,including investigations on the research and development of micro-current detection theory at home and abroad,and an introduction to some mature micro-current detection instrument design methods.Secondly,the hardware circuit of the micro-current detection instrument is designed,and the high-impedance negative feedback I / V amplifier circuit is used as the signal amplifier of the gas sensor and the pre-input circuit of the single chip microcomputer.The AD?C847 single-chip microcomputer with 24-bit high-precision built-in AD is selected as the microcontroller,and functional blocks such as shift circuit,LCD display,USB storage and WIFI data upload are designed in the system to improve the instrument function.Then the paper introduces the development environment of the single-chip microcomputer program,designs the work flow chart of each part of the single-chip microcomputer and programs for the single-chip microcomputer to complete the above functions,including the main program design and the subprogram design of the function blocks of each part.Finally,the shortcomings appearing in the design and work of the micro-current detector,and the direction of improvement are proposed.