Static Strain Gauge Based On LM3S9B96

The stress-strain measurements of structural components in room temperature are divided into static and dynamic due to the different loads. When the load changes slowly, the stress and strain of the components are slowly varying with the time which belongs to static stress-strain measurement.Static strain measurement is often used in key engineering structures, such as aircraft structures, boilers, steam turbines, express train structures and so on. These structures need strict tests to detect stress and deformation after manufacture, in order to make sure to meet the requirements of strength, stability and safety margin. Static strain measuring devices are also massive used in the static and fatigue tests of various materials.The strain data acquisition devices on the market most are the general-purpose for both static and dynamic measurements. They are DSP+FPGA or MCU+FPGA architecture and the precision is up to24bits. When a large number of measuring channels are needed, the system cost will be very high. Therefore, to develop a market targeted new type static strain gauge has a great significance. Because it is not only cheap but also can meet the accuracy requirement and can easily achieve a network of multi-channel.This paper completed the design of ARM processor-based static strain gauge through reviewing domestic and foreign literatures and comparing different product specifications and performances. This device has16-channel inputs, long measuring wires compensation, Ethernet interface and SD card for local storage capabilities to meet the requirements of massive measuring points, convenient network acquisition and real time data redundancy. Its acquisition accuracy is12bits. The system resolution is up to5με and support configuration of120Ω quarter-bridge strain test. So, it can achieve low-cost, multiple occasions and large-scale application.Firstly, the research background and significance of the topic have been described. The present domestic and foreign strain acquisition systems were analyzed. The structures and modes of different usages and scales of the strain gauge system have been clarified. On the basis of market research, products positioning and R&D capabilities, technical specifications were put forward. Secondly, the principles and methods of static strain measurement were introduced. Hardware and software designs of the device have been completed.Cortex-M3core ARM processor LM3S9B96produced by TI company was selected as the central processor. Its unique instruction system, powerful data processing capability and a wealth of on-chip interface resourses have greatly meet the functional and performance requirements of the static strain gauge. This paper completed the hardware circuit design and explained the functions. Circuit schematics of all parts and PCB layout were provided.Flow charts of the main program have been drawn. Each task module source codes have been programmed. TCP/IP protocol has been cut and transplanted, so network communication can be used freely. SD card with SPI mode communication has been accomplished. The strain data has been arithmetic processed which is convenient for subsequent analysis.Finally, a test circuit board has been made and debugged. Test data has been obtained. The design feasibility and rationality have been verified. A summary of this paper elaborated the completed work, characteristics and significances of the job. Meanwhile the design deficiencies and improvement idears have been pointed out.