The Design Of The Automatic Verification System For Hand-held Digital Multimeter

In the mission of spaceship launch test, the hand-held digital multimeter is still a major electricity measurement tool. According to national hand-held digital multimeter verification regularity, digital multimeter must be verifed periodically. As the hand-held digital multimeter without programmable interface, its verification relies on manual quality previously. But the hand-held digital multimeter functions such as its test parameters and test range are more complex, manual verification are often susceptible to misreading, low efficiency and easy to lead judgment error and other issues.In this paper, the hand-held digital multimeter has been studied, and the image acquisition device has been designed and developed to obtain the hand-held digital multimeter's reading image. A series of computer digital image processing and recognition methods are used, including positioning and segmentation of digital image region, tilt correction, graying, gray stretch, binary, median filtering, the gradient sharpening, edge detection, image segmentation, and digital identification. In order to solve the communication problem between the computer and the hand-held digital multimeter without interface, the value image of the hand-held digital multimeter is processed and identified by program. Then, using the approach of testing meter with the source, combined with the standard source of program control, the paper hss developed an auto-verification system of the hand-held digital multimeter, which can verify, process of data, and report automatically.The test results have proved that the system design is feasible. The system has the characteristics such as great real-time ability, high recognition rate, fast and accuracy reading in verification. The system can meet the daily requirements for accreditation and has greatly improved the efficiency and quality of verification.