Design And Development Of Automatic Test System Of PLC Module

With the advent of information age, automatic test technology is gradually coming into our view. Because of the high test speed, well real-time characteristic, high measurement accuracy and other features, it has been extensively applied in manufature, military and other fields, and becomes an important measure about product test and quality control. The development of automatic test technology promotes the advancement of modern science and technology.The proposed project is based on the need of a company in Dalian which produces PLC module, in order to solve the disadvantage of the original manual calibration mode that manual calibration of the efficiency is low and the rate of misuse is high, relying on the test norms and standards provided by the company, design and develope a set of PLC Module Automatic Test System(PLCATS). Test items of the system includes PLC communication test, the internal parameters calibration, real-time clock test, digital input and output(DIDO) test, LED light board test, analog input and output(AIAO) calibration, cold junction temperature compensation calibration and fuction block test.Based on the analysis of system requirement, it proposes PLCATS should be versatile, scalable, automatic test, convenient operation and so on. The configuration structure of entire test system is proposed from the two aspects of the network topology and architecture. According to the test workflow feature and analyzing the test complexity of each link based on the test operation workload, the system is divided into four stations, which are respectively responsible for AI calibration, AO calibration, cold junction calibration and other items test. Use the standard PLC modules provided by company as the test equipment and control equipment to realize the tested channel switching, analog signal measurement, digital input and output and other functions, and combine with the Agilent34401A and Fluke5500A as the signal measurement and output devices to construct the hardware test system of each work station, and design the common interfaces to meet the test connection of the various PLC modules. Each work station keeps the relative independence, and the system connected by ethernet forms the LAN automatic test system. The design of software system adopts the software modular design and object-oriented programming ideas and the software structure is divided into four parts as parameter configuration, data acquisition, procedure testing and database management, and design the communication, test standard, database operation and other functional classes. Apply UDP and Modbus protocols with EPA(Ethernet for Plant Automation) message to achieve the communication between PLC equipment and computer, and use the SCPI(Standard Commands for Programmable Instruments) to control the programmable instruments automatically. Relying on the requirements of each test items, it designs the test and calibration sub-modules in the procedure testing, in order to complete each test function, real data storage, fault warning and other functions. The line shield in hardware and digital filter in software are applied in the system in order to reduce the measurement error. Use the ActiveX control technique to achieve the perfect combination between fuction block test and ERP(Enterprise Resources Plan) system software.The PLCATS quoted has been accepted and applied in the produce department of company, which has a certain extent of reference value and practical significance for the current PLC module automatic test system design.