We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this repo...We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this report, we demonstrated a simple but effective method to compensate for this parasitic capacitance by adding a compensator circuit consisting of an inverting amplifier and a capacitor. The capacitor is connected in series with the inverting amplifier and the compensator is connected in parallel with the quartz tuning fork. The resonance curve of the system measured after adding the homemade compensator resembles that of a pure RLC circuit, meaning that the stray capacitance is successfully eliminated. Furthermore, we tried to use our equipment to measure PDMS sample and got clean data. This system can be further combined with confocal microscope and diamond with NV defect to build scanning NV magnetometry.展开更多
With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the poll...With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the polluted surface of the CVT becomes noticeable.The equipotential shielding CVT(EPSCVT)was proposed and designed by the authors to mitigate these effects.An improved conceptual design option of the EPS-CVT is presented in this paper with special references to this study to improve the shielding effect without the increase of shielding capacitance.A proposed method of non-uniform capacitance configuration can improve the shielding effect significantly without an increase of the external shielding capacitance.Based on this achievement,the potential difference and the capacitive current exchange between the internal measuring system and external shielding systems are significantly reduced.In the evaluation of the shielding effect for the influence of stray capacitance,compared with a conventional CVT with equal capacitance,EPS-CVT can reduce the measurement error by two orders of magnitude.In addition,the measurement error caused by the leakage current can also be greatly reduced,especially for the reduction of the phase angle error.Based on the improved design method,a design scheme for an engineering application is proposed which can achieve effective shielding while ensuring as good a technical performance as the existing CVT.展开更多
文摘We have built an atomic force microscope using a quartz tuning fork as sensor. The excitation method we adopted, the electrical excitation, introduces stray capacitance into the signal-processing circuit. In this report, we demonstrated a simple but effective method to compensate for this parasitic capacitance by adding a compensator circuit consisting of an inverting amplifier and a capacitor. The capacitor is connected in series with the inverting amplifier and the compensator is connected in parallel with the quartz tuning fork. The resonance curve of the system measured after adding the homemade compensator resembles that of a pure RLC circuit, meaning that the stray capacitance is successfully eliminated. Furthermore, we tried to use our equipment to measure PDMS sample and got clean data. This system can be further combined with confocal microscope and diamond with NV defect to build scanning NV magnetometry.
文摘With the increase of the operating voltage and enlargement of the size of the capacitor voltage transformer(CVT),the additional measurement error caused by stray capacitance coupling and leakage current along the polluted surface of the CVT becomes noticeable.The equipotential shielding CVT(EPSCVT)was proposed and designed by the authors to mitigate these effects.An improved conceptual design option of the EPS-CVT is presented in this paper with special references to this study to improve the shielding effect without the increase of shielding capacitance.A proposed method of non-uniform capacitance configuration can improve the shielding effect significantly without an increase of the external shielding capacitance.Based on this achievement,the potential difference and the capacitive current exchange between the internal measuring system and external shielding systems are significantly reduced.In the evaluation of the shielding effect for the influence of stray capacitance,compared with a conventional CVT with equal capacitance,EPS-CVT can reduce the measurement error by two orders of magnitude.In addition,the measurement error caused by the leakage current can also be greatly reduced,especially for the reduction of the phase angle error.Based on the improved design method,a design scheme for an engineering application is proposed which can achieve effective shielding while ensuring as good a technical performance as the existing CVT.
