Study on time delay measurement technology in distributed test system

The distributed test system is a complex control system which is based on computer technology, network communication technology and sensor technology. In the distributed test system, each testing device communicates with the data control center in a wired or wireless way, and realizing the unified control of the test equipment and the centralized processing of the collected data. Different from the independent test system, in the network distributed test system, each test device needs to communicate with the data control center to complete the corresponding test task. In the signal transmission, different transmission distances will cause the difference delay while the data control center has sent the homologous signal to different test devices. Furthermore, if the test devices in the system do not have a unified time base, the test data will not be able to reflect the true information in the reason of clock difference. Therefore, all the test devices in the network need to know the delay between themselves and the data control center in order to ensure the real-time information between each other. That is, all the devices in the test network need to keep clock synchronization. The authors presented a time delay measurement method which based on FPGA, in the view of the requirement of clock synchronization in distributed test system and the requirement of high precision delay measurement in transmission line of linear topology. The realization principle of delay measurement method from software and hardware is expounded in detail, and the function simulation and experiment verification are carried out. The experimental results show that this method is simple and practical, and it can realize the high-precision delay measurement of the transmission link. It is an effective delay measurement method in the distributed test system.