Building Of Portable Vibrator System And Its Signal Processing Research

Portable vibrator system is a kind of portable vibration measuring instrument, which not only can be used for calibrating many sorts of vibration sensors including acceleration, speed, displacement sensors, but also can calibrates vibration measuring instrument, vibration monitoring system and data acquisition system composed of these sensors. This system has the characteristics of small volume, high accuracy, simply operation, convenient usage etc., and can be applied in the field or laboratory.This system is mainly composed of signal generator, power amplifier, vibrator, standard piezoelectric acceleration sensor, charge amplifier, A/D converter module, control and display module. MSP430F427, integrated with 16bit∑-△A/D module, is utilized as key controller to realize A/D function, control system running, and have Chinese liquid crystal indicator to display related parameters. Main research work of each chapter is outlined as following:Firstly, from the design requirements of the portable vibrator system, the total structure and working principle of this system is studied. According to this, a mathematics model about it is established, from which the calculation formula of each parameter is deduced.Then, from the angle of the working principle and the realization, each function module in portable vibrator system is mainly designed. The working principle of piezoelectric acceleration sensor is illuminated, and the familiar types are introduced too. According to piezoelectric effect, when a force presses on the piezoelectric material of sensor, the sensor will output electric charge (or electric voltage). Therefore, its basic measurable parameter is not only pressure but also other parameters that can be transformed into pressure, just like acceleration etc. Pressure distortion of piezoelectric material includes thickness distortion, length distortion, volume distortion, and shearing distortion. According to the types of distortion, there must be corresponding structure of sensor. Currently the most familiar ones are the compression-type based on thickness distortion and the sheared-type based on shearing distortion. The amplifier types, used for piezoelectric acceleration sensor, are introduced. And by deducing formulas, the differences in function between voltage amplifier and charge amplifier are illuminated. Voltage amplifier has the advantages of simple electric circuit, few elements, cheap price, and credible stability etc.; disadvantages are also exit, such as measuring accuracy is greatly influenced by the electric cable, which connects the amplifier with the sensor. Under certain condition, charge amplifier's output is independent of the electric cable, and its frequency response is nice no matter high frequency or low. But it is more expensive, its electric circuit is more complex, and its adjustment is more difficult too. Then, according to the characteristics of portable vibrator system, charge amplifier is adopted as post-amplifier. At the same time, based on the basic working principle of the charge amplifier and the analysis of the general charge amplifier YE5850, charge amplifier testing PCB, used for portable vibrator system, is designed. The signal processing circuit board is designed based on MSP430F427, which is used as the whole control module of system, providing A/D channels for acquiring the output voltage signal of charge amplifier. The Chinese liquid crystal indicator is adopted to design man-machine interactive interface, through which vibration parameters are displayed. Some anti-interference technology is taken as following: routing technology between analog ground and digital ground in PCB, using shielded cable to deliver the signal, and connecting shielded box of charge amplifier to the ground etc., these measures reduce the influence of the external world and improve signal-to-noise ratio.At last, the unit test of each function module is introduced, and then the testing result of the whole system is given after the illumination about its testing method. The unit test of each module includes two aspects: 1) identify the key parameters of the charge amplifier through a series of experiments, and at the same time make a performance comparison with YE5850. 2) test the SD16 module, which is integrated in MSP430F427. A software filter is added to remove accidental noise appeared in the A/D processing. After the test of two function modules, the system test is carried out at Beijing metering and measuring science institute and the test data is obtained.