1/1/2024 0 Comments Quartz tuning fork sensorTo use the high Q factor of the tuning fork, the two prongs should be excited in the anti-phase mode. 9 To date, the high Q factor of a tuning fork has not been well exploited in nc-AFM. 8 In contrast, the two-prong force sensors with a tip imaged only step structures of Si(111) 6 and highly ordered pyrolytic graphite. 6 To overcome this problem, Giessibl developed the qPlus sensor by fixing one prong, so that it would not oscillate, and observed atom-resolved images of Si(111)–7 × 7 using the oscillation of the other prong. However, when an AFM tip is attached to one prong, the oscillations of two prongs become unbalanced through the detuning of the resonance frequencies of the prongs, resulting in a lower Q factor. This is because the anti-phase mode cancels the distortional oscillation amplitude at the join, leading to low energy dissipation at the join. 7 The Q factor of the tuning fork in its resonant state, the anti-phase oscillation mode of the two prongs, is greater than that in the in-phase oscillation mode and that for the one-prong sensor. One of the force sensors is a two-prong type, 6 and the other is a single-prong type, called the qPlus sensor. The tuning fork comprises two prongs joined at their ends the resonance frequencies ( f TF) of the two prongs are precisely tuned to the same frequency (typically, f TF = 32 768 Hz). It is proved that it is possible to construct a miniature quartz tuning-fork temperature sensor with high sensitivity and small non-linearity.Up to now, two types of force sensors, based on quartz tuning forks as the oscillator with high Q factor, have been frequently used in nc-AFM. The temperature sensor based on quartz tuning-fork thermo-sensitive resonator is mounted in a standard holder for use from −30 degree C to 160 degree C with an accuracy of 0.05 degree C and a high resolution of 0.001 degree C. Using ZYtw-cut can bring the temperature coefficient up to 70ppm/(degree C) and make power consumption lower. The results obtained from the experimental investigations show the method which synthesizes many factors to design quartz tuning-fork temperature sensor. Precise temperature versus frequency analyses of resonators have been carried out and Least Mean Squared (LMS) curve fit algorithm is applied to compute the temperature values quantitatively. This type of sensor designed with a new ZYtw-cut is proved that working at flexural vibration mode was better than at the others modes. In order to optimize the design of quartz tuning fork temperature sensor, finite element method (FEM) is applied to model optimum tuning fork geometry, tine tip and tine surface electrode shape and thickness with a resonance frequency close to 32 kHz and a series resistance value of 40 kΩ as design targets.
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