Research On QCM Liquid Detection For Precision Signal Generator

Quartz Crystal Microbalance is a new type of mass sensor with high sensitivity; it can be used to measure tiny mass change at the precision of nanogram. Because of its wide operating temperature range, high stability, small size and many other advantages, Quartz crystal microbalance has been used in biochemistry, environmental monitoring, surface chemistry and many other fields of application at present. However at this stage, QCM is mainly achieved through oscillating circuit this way, QCM as a resonator, the value of Q is limited, stability is not high. Random drift frequency may be greater than the frequency change caused by the change of quality. In this case, using high precision frequency source, which working in sweep frequency mode can weaken this problem. Therefore, the research on QCM signal generator with small volume, low price, portable and high precision is particularly important.Signal generator is a kind of electronic instrument, which is used with a high frequency in the field of electronic field. It is widely used in teaching and research, product development, remote sensing etc. Direct digital frequency synthesis is the third generation of frequency synthesis technology, which uses the technology of digital control the signal’s phase increment, which consists of the phase accumulator, waveform ROM table, D/A converter and a low-pass filter. Compared with the traditional frequency synthesizer, not only has the traditional frequency synthesizer unmatched high resolution, also has fast frequency switching, continuous phase while switching, low noise, low cost and many other advantages.This article describes the development history of frequency synthesis technology, and systematic exposition of the basic structure and working principle of DDS, rational use of DDS technology according to the system metrics, design a signal generator with simple structure and excellent performance, which uses AD9854 chip of ADI company as the core, takes ATmega32 chip of Atmel company as the control machine, describes in detail the system’s hardware and software design, the realization of the specific circuit.In this paper, based on the overall design of the signal generator, introduced the AD9854 signal generator module, MCU module, power supply module, filter module, download ISP interface module, JTAG online simulation module, and serial ports communication module. The system software part respectively introduces the PC control module, and frequency control module, including the user interface, the transmission of AD9854 conversion, frequency control word design of AD9854 and key scanning module. Finally debugging and testing of the system, and analysis of the test results and errors.