Development Of Air-leakage Detector’s Calibration Device

As industries develop rapidly in China, high quality sealing products have become a big concern. There are more and more sealing-checking devices in the market. However, it lacks of calibration systems and the authenticated national standards. The regular procedures, bases on the standard JJG875-2005 of digital pressure gauges, only calibrate the pressure output and neglect the pressure difference. Thus, it does not meet the requirement of calibration. This thesis illustrates a possible standard calibration system which calibrates pressure gauges and sensors of pressure difference at the same time. It also makes the original data of the sealing-checking devices track able. This thesis includes the followings:⑴ Via analysis of structure and mechanisms and modeling of relationship between leakage and pressure difference, the calibration system of sealing-checking devices was designed. It consists of three parts, the control system, standard pieces of calibration and the pressure adjustment system. The control system includes the Mitsubishi PLC, a LCD touch screen and the corresponding calibration programs.⑵ The sensor of pressure and pressure difference was chosen according to the precision and made by Setra Systems, Inc.. It was connected to a high quality AD converter that fulfills the precision demand of calibration.⑶The repeatability and stability were examined and the relative uncertainty was determined.In the examination stage, the values of pressure and pressure difference shown by the system were correct. The traditional calibration method indicates that the system meets the level 0.1 precision standard. The standard leakage test also sustains this result. The uncertainties were calculated to be U95rel=0.29%and U95rel=0.12%, which met the requirement of being less than 1/3 of the allowed error. Therefore, the calibration system, innovated in this project, met the expected requirement. It provides the foundation of regulation of sealing checking devices and enables further research of calibration system.