The Design Of Multifunction Charge Generator With High Accuracy

Piezoelectric sensor has been widely used in the measurement of dynamic parameters such as vibration, acceleration, pressure. The application of charge amplifier is also widely used as the signal modulator, for which the performance indicator is more and more rigorous.However, the main technical indicators need to be re-examined after long-term used of the charge amplifier. Charge generator can generate standard charge which is used to test the charge amplifier or adjust the piezoelectric test system.In this paper, a high precision multi function charge generator is presented by using the direct digital frequency synthesis technique for the problems like large volume, low precision,inconvenient carrying and so on. The instrument used MSP430 microcontroller as the controller, and it can output 6 kinds of wavefirms. The charge generator can choose output voltage signal or charge signal which can meet the calibration needs of high-precision charge amplifier and the piezoelectric test system. The whole system power is supplied by batteries,which can carry on and provides convenience for scientific research work. The contents of this paper are followed:Firstly, by comparing the principle of the direct frequency synthesis technology, indirect frequency synthesis technology and the direct digital frequency synthesis technology.advantages of direct digital frequency synthesis technology are obtained. The digital frequency synthesis technology based on the address counter is used as the design scheme finally.Secondly, according to the overall design of the system, this paper analyzes the design principles of the main control circuit, power circuit, waveform generation and control circuit,human-computer interaction circuit, signal processing circuit and power supply circuit. According to the overall system flow chart, the program of various modules is designed by C language which realized the human-computer interaction mode between thekey and the LCD display.Thirdly, the error sources of the high precision multi-function charge generator are analyzed, and the output frequency, amplitude, baseline and integrated errors of system are calculated. After debugging the high precision multi-function charge generator, the test results are in the range of theoretical error, which indicates that the design of the system meets the expected requirements.