Research On Automatic Calibration System For Pointer Meter And Its Design

Pointer meter is a common type of measuring instrument. Due to easy construction, convenience and low price, pointer meter is frequently applied in the regions of personal, industries and science experiments. With using pointer meter, calibrations are needed at regular intervals for keeping its correct readings. Manual labor, which could cause high human expenditure however low accuracy and efficiency, was used in most situations. With the speed development of computer vision, an automatic calibration system based on computer vision is the most valuable scenario to resolve this problem. This dissertation is introduced on the research of an automatic calibration system, including a study on a calibration method and the system's design.In this dissertation, a sliding window method for automatic calibration is presented. The method is an implement of orientation strategy: focus the detected target from the whole source image to a small window, and pay attention to the ROI(region of interest), making an efficient process of pointer feature extraction with an accurate pointer orientation. Hough transform line detection and an improved Hough transform approach based on orientation are used to detect angle, and then the detected angle is mapped to an actual value with a predefined angle-value mapping.The dissertation also discusses the design of the automatic calibration system, including the hardware frame's construction and the design of software system. The hardware frame is constructed within: a camera, an illumination, a fixed platform, a meter and its power supply. Software system's design is composed of a general design and a functional modules design. Functional modules include: image capture and preprocess module, meter type module and automatic calibration module.The experiment has assured the availability of the sliding window method. The experiment has two parts: verification to the fixed calibrated points, and automatic reading to the un-calibrated(arbitrary) points. The experiment result shows that the method is, compared to the industrial standard, adequate both to meter calibration and automatic reading, and overcome those inadequacies of human eye in inaccuracy and inefficiency.