| In DMMs calibration work,a handful of DMM can accomplish full automatic calibration through program control,while more than 90%of the hand-held DMMs can not be programmed through the interface,only through manual or semi-automatic calibration,with low efficiency and high error rate.At present,in the research of automatic calibration system of digital multimeters,only the operation of knob switch is not automatic.Accordingly,this project introduces a set of automatic calibration system,which uses machine vision instead of human eyes to read the display value,replaces manual line change in the calibration process with wiring switching device,substitutes human hands to operate the knob for manipulator,realizes the operation of knob switch from the above three aspects,and finally establishes a software platform for automatic calibration of automatic range DMMs.The main contents of this project are as follows:(1)The introduction introduces the research status and background,through the analysis of calibration methods and functional requirements,the overall technical scheme of the system is formulated,the hardware composition and overall architecture of the system are described,how to solve the problems involved in the knob operation of the manipulator is analyzed,the control scheme of the functional module is discussed,the system software architecture and calibration process are designed.(2)The second chapter focuses on the automatic shift of the knob switch of DMM.In this project,the cross cursor and target matching method are used to seek out the accurate positioning of the manipulator,the positioning error is better than 1mm;through the torque detection and Kalman software filtering algorithm,the rotary function of the knob switch is detected,and the passing rate is over 90%;The rotating position of manipulator is determined by the angle measurement method of template matching technology,and the passing rate is over 90%.(3)This project studies and designs a mechanical structure which integrates the perceptible information of three kinds of sensors,and realizes the operation of the knob by the manipulator.It can realize the 4-DOF movement in the range of 300×300×200mm The embedded main controller circuit is designed,including torque detection,relay array,hall device application circuit design.The robot rotation control,automatic wiring function,position detection and limit control are realized respectively.(4)In the development environment of Lab VIE W,the measurement management software is built,and the machine vision recognition method is studied.The data collection,analysis and processing are realized.Make up 50%light with ring light source,and the success rate of digital identification is over 90%.The program of embedded main control system is designed with C language,which can switch logic of relay and 4-axis motion control of manipulator.The above work builds the foundation of software and hardware interaction.(5)Test the FLUKE series automatic range DMMs,the success rate is over 90%,and then compare the calibration results of manual and automatic tests.The uncertainty component of the measurement results introduced by the system only affects the calibration of the low range resistance of the 4-digit half digital multimeter,but has no impact on the calibration results of other calibration items.This project attempts to use the manipulator to operate the knob in the automatic calibration system of DMM to make up for the shortcomings of semi-automatic calibration,and verify its feasibility.This method solves the problem that the traditional hand-held DMM can not be calibration by program,and accomplish the automatic calibration. |
PDF Full Text Request