Development Of Automatic Verification&Calibration System For Digital Multimeter

Digital multimeter as the most common tool is always used in the modern electronics measurements and electric measurements,it is mainly measure voltage, resistance and current.The accuracy of DMM’s indicating value will directly impact the product’s quality,so DMM must be verified or calibrated according to the cycle.This article first elaborated three general verification/calibration methods of DMM,then it analysed the measurement uncertainty, finally it introduced the basic functions and:esting process of the special measurement software MET/CAL.After consulting the merits and faults of current world automatic test software based on the text and according to the practical requirement in DMM’s calibration work of the metrology department, author design the automatic verification/calibration system of DMM. This system not only avoid gross error of human negligence, and make the DMM’s calibration work much easier and more convenient.DMM automatic calibration system consists of two parts,hardware constitution and software design, hardware part includes electrical metrology standard5720A, PXIe-8135controller, shielding GPIB cable, input devices, monitor and printer; Software part is based on the LabVIEW programming platform. The procedure written by author can control the whole system to automatically verify or calibrate DMM. In the process of verification and calibration,this system can acquire test data, calculate error and evaluate uncertainty, finally issue the test report.By applying DMM automatic calibration system for the calibrating or testing the high accuracy DMM’s, indicates that the system achieved the DMM’s automatic verification and calibration.This system is not only easy to operate, convenient to use, and reflects the characteristics of high accuracy and high stability in the process of testing the whole system.The system’s technical indicators satisfy the requirements of metrological standard equipment in the national metrological verification regulations and calibration specification, and it achieve the desire goal.