The Research And Development Of An Automatic Testing System For Railway Safety Relays

Railway signal is very important as the cerebrum and nerve of the railway. Safety relays are rather important executive components in a railway system, whose electrical characteristics must be tested timely. The electrical characteristics of railway safety relay are mainly involved with operating value, releasing value, reversing value and so on. Conventional relay testing instrument has many defects such as low-density of integration, high straggle of parameters, unreasonable placement of structures, semiautomatic or manual testing, low precision and reliability, and specificity.According to Chinese Standard "Testing Methods for Railway Safety Relays (GB/T 6902-2001)" and "AX Serial Relays (GB/T 7417-2001)", one automatic testing system (ATS) aimed to relay electrical characteristics has been realized for a variety of AX relays. This system possesses some good characteristics like wide dynamic range and high measuring precision. Design and development of hardware and software are main job of the subject. For hardware part, a conditioning circuit for pretreating analog signal is developed which is constituted with voltage-current sensor, amplifier OP07, programmable gain instrumentation amplifier PGA204, analog switch MAX4534 and so on. A 24 bits S-ΔADC module of model AD7714, which is integrated with programmable gain and digital filter, has been used. An 8 bits microcontroller with model PIC16F877 acts as the main controller. All modules are connected in distributed control system via RS-485 serial bus. For software part, monitoring and testing function has been realized on PC whose compiling environment is composed of WIN32 platform, compiler Qt4.2.1 and Microsoft Visual Studio .NET 2003.Present writer has studied and developed a set of hardware and software system which can high efficiently achieve the test of electrical characteristics for all 25 species AX serial relays. If one species of relays has been chosen on PC (or input the parameter value of electrical characteristics), the relay electrical characteristics can be tested, displayed, stored and printed automatically. Theoretical and applied progress has been made in applying embedded technique to developing automated intelligent testing system for railway safety relay in the subject. The production cost can be reduced, the operating efficiency is increased, and the economic value is rather high.