Adjustable-amplitude quartz crystal microbalance self-excited oscillation circuit

Abstract

The invention discloses an adjustable-amplitude quartz crystal microbalance self-excited oscillation circuit comprising a loop formed through an exciting signal feedback module and an amplitude regulating module. The exciting signal feedback module comprises an exciting crystal amplifier, a voltage follower, a subtracter, a low pass filter and an automatic gain control amplifier. The amplitude regulating module comprises a buffering amplifier, a voltage regulator and an amplitude amplifier. Sinusoidal signals produced by loop self-excited oscillation excite quartz crystal to oscillate, and a quartz crystal oscillation frequency signal Vf and an equivalent resistance signal VR are extracted and fed to outside for measurement. The amplitude of the exciting signals can be changed by regulating the voltage regulator in a numerical controlled manner, and the crystal oscillation amplitude regulation can be implemented.

Description

technical field [0001] The invention relates to micromass measurement technology, in particular to a self-excited oscillation circuit of a quartz crystal microbalance with adjustable amplitude. Background technique [0002] Quartz Crystal Microbalance (QCM) is a very sensitive thickness-shear piezoelectric sensor, the real-time detection limit of mass change can reach nanogram level, and it can use piezoelectric resonance and crystal surface Modification, to realize the dynamic regulation of the mechanics and chemistry of the crystal surface and mechanical sensing, has been widely used in the fields of chemistry and microbiology. [0003] Among the current commercial QCM devices, such as RQCM and PLO-10i of Maxte Corporation of the United States, QCM934 of Seiko Corporation of Japan and QCM200 of Stanford Research Systems Corporation of the United States, etc., the drive measurements are all based on phase-locked or self-excited oscillation circuits, which can measure quartz...

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Problems solved by technology

However, none of the above-mentioned QCMs can adjust the intensity of the excitation signal applied to the quartz crystal, so the oscillation amplitude of the quartz crystal cannot be adjusted, and the shear force of the quartz crystal on the load on it cannot be adjusted, so it cannot be used to detect different shear forces. The morphology and mechanical response of the loading on the lower crystal surface, thereby revealing its mechanical properties, and in-depth research on the interaction between molecules or atoms, particles or biological particles and the contact interface of quartz crystals

[0004] In order to achieve amplitude adjustment, the patent "Measurement and Application of Molecular Interaction" (ZL00806533.0) of Cambridge (UK) Acubio Co., Ltd., and the patent "Quartz Crystal with Controllable Oscillation Amplitude" of Wu Kun et al. Microbalance Attenuation Factor Measuring Device" (ZL2006 2 0075035.2), both proposed a phase-locked oscillation QCM device that can change the output amplitude of the excitation signal generator, but the two do not escape the inherent limitations of phase-locked oscillation: that is, a device for The signal generator that generates the excitation signal, and continuously corrects the frequency of the output signal of the signal generator through a phase detection and frequency selection circuit, so that it is locked on the resonant frequency of the quartz crystal, so its circuit ratio is based on the frequency selection of the quartz crystal The self-excited oscillation circuit of the device is complex

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