Design Of Multi-channel Magnetoelastic Sensor Detection Instrument Based On ARM

Magnetoelastic sensor is based on magnetostrictive principle of ferromagnetic materials. When placed to an external alternating magnetic field, the magnetoelastic sensor is excited, and it converts the magnetic energy to mechanical energy, which deforms the sensor and drives it mechanically vibrate along its length. As the magnetoelastic sensor is also magnetostrictive, its vibration in turn generates a magnetic energy which can be detected remotely by a coil. If the frequency of external magnetic field is the same as the sensor’s mechanical resonance frequency, the vibration amplitude will reach peak. The sensor resonance frequency is related to its surface mass loading, the environment temperature, viscosity and other factors, so the shifting of resonance frequency can reflect the change of response signal. The magnetoelastic sensor is completely passive, and there is no physical connection between the sensor and the detection circuit. The wireless, passive features make magnetoelastic sensor wide application prospects in several areas, such as no-destructive detection, in situ and in vivo analysis.With the development of information, networking and intelligent, embedded technology represented by ARM has been widely used. Compared with MCU, ARM’s high frequency and speed, low power consumption, rich external resource and portable operation system make it very easy to increase or cut the corresponding function. The embedded Linux has the characteristics which are stable, open source code and powerful multi-task management, and it has become the main research directions of embedded system.Magnetoealstic sensor researched on this thesis is mainly used in biochemical analysis, and a multi-channel magnetoelastic sensor detection instrument base on ARM-Linux is designed. This article firstly analyzes the significance of magnetoelastic sensor research and the current status of study at home and abroad, then the working principle of magnetoelastic sensor is introduced and several methods of measurement are compared. The requirement of multi-channel magnetoelastic sensor detection instrument is determined in the conceptual design phase, using an ARM9-based hardware platform. In the part of system hardware design, schematic diagram is introduced according to system project, and the principle of main function modules is analyzed in detail. Software design is adopting embedded Linux which is the most widely used system management platform, and the U-Boot, Linux kernel and root filesystem migration process is also introduced. Furthermore, the development of Linux kernel device driver is in-depth studied. We have also discussed how to design user applications under the Linux operating system environment. The application framework and window systems of graphical user interface are provided by Qt/Embedded design tools. Finally, we use the instrument to detect and analyze the concentration ofα-amylase.The multi-channel magnetoelastic detection instrument introduced in this thesis is stable and reliable operation. It can measure 4 sensors continuously, real-time display the measuring results and analyze quickly and accurately, with a friendly interactive interface to facilitate user. It is also possible that the measurement data can be saved as a text file and transmitted to PC through network interface.