Tracking testing system of resonant frequency of quartz crystal microbalance and method thereof

Abstract

The invention discloses a tracking testing system of the resonant frequency of a quartz crystal microbalance and a method thereof, the tracking testing system comprises an analog circuit testing network and is characterized in that the tracking testing system further comprises a digital frequency synthesizer, a homologous frequency multiplication signal generation module, a high-speed analog-digital converter ADC, a signal processing module and a feedback tracking module, wherein the high-speed analog-digital converter ADC is used for generating a frequency multiplication signal which is homologous with a driving signal and has the frequency of 4 / (2N plus 1); a voltage signal outputted by a sampling module is amplified by an operational amplifier and then directly enters into the high-speed analog-digital converter ADC for carrying out conversion and output; the signal processing module is used for calculating the serial complex admittance of a QCM chip according to Kirchhoff laws, and approximately calculating the difference between the current frequency and the series resonant frequency of the QCM and the serial impedance of the chip; and the feedback tracking module is used for changing the output frequency of the digital frequency synthesizer, leading the output frequency to approximate the serial resonant frequency of the QCM, and repeating the implementation for realizing the tracking of the serial resonant frequency of the QCM.

Description

technical field [0001] The invention relates to a testing method for a quartz crystal microbalance (QCM), in particular to a tracking test system and a method for resonant frequency of the quartz crystal microbalance. Background technique [0002] Quartz crystal microbalance is a micromass detection technology that applies the principle of piezoelectric resonance. Its basic principle is to use the piezoelectric effect of quartz crystal: applying mechanical force on both sides of the wafer will cause the charge center of the lattice to shift and polarize, and an electric field will be generated in the corresponding direction of the wafer; otherwise, if When an electric field is applied to the two electrodes of the quartz crystal, the wafer will be mechanically deformed. If the electric field is an alternating electric field, it will cause mechanical oscillation in the crystal lattice. When the alternating frequency is consistent with the natural mechanical oscillation freque...

AI Technical Summary

Problems solved by technology

[0009] The main disadvantage of this type of circuit is that the QCM and compensation components are connected to a more complex network, which includes operational amplifiers

The non-ideal characteristics of the operational amplifier itself, such as input current, input impedance, and hysteresis, will affect the phase of the UA signal and interfere with the series resonance. At the same time, the influence of the parasitic capacitance and inductance of the cable and the contact resistance of the quartz wafer electrode cannot be eliminated. ;Secondly, the path of signal measurement is too long, and it needs secondary amplification, square wave shaping, phase detector, low-pass filter, and analog subtractor to get the phase detection result. The noise and error of these analog components will significantly reduce the measurement accuracy

Images