Papers by Keyword: Scanning Frequency

Abstract: Vibrating wire sensor signal acquisition system is widely used in the fields of water conservancy dam, slope, construction, mining and so on to measure osmotic pressure, soil pressure, strain and other physical quantities. This paper studies the single coil vibrating wire sensor signal acquisition system,which uses the STM32F103 core processor generating a low-voltage feedback PWM signal to excite vibrating wire with scanning frequency, after signal amplification, filtering and signal normalization through the frequency measurement module, and ultimately achieve frequency measurement. The system can improve the traditional vibrating wire acquisition instrument, so as to achieve fast and efficient and reliable long-lasting measurement. According to some simulation and designed circuit, the measured data and diagram can verify the feasibility of the method.

Abstract: There are two ways of excitation on steel-string sensor—high-voltage plucked excitation or low-voltage scanning frequency excitation. But both of them have disadvantages. The disadvantages of high-voltage plucked excitation are that it has a large damage to sensor, the signals got through this way attenuate fast, and measurement accuracy of the signals is poor. On the other hand, low-voltage sweeping excitation scans a long time and signals got though this way are hard to catch. This paper proposes a kind of feedback type low excitation method, which is pre-excite a sensor with a lower voltage on plucked vibration, and use vibration frequency got from this way as output of the excitation driver to vibrate the sensor for the second time. Because the feedback signal frequency is approximate to the real one, the string can reach a resonance state in a very short time. The optimal excitation strategy is verified by a new designed exciting and measuring circuit. It is confirmed that resonance amplitude can be larger in a shorter excitation time by this way, and result in an enhanced anti-interference ability, reduced the cost of signal processing circuit, increased available measuring time and improved the accuracy of frequency measurement.

Abstract: Based on the calculation formulas of heat treatment temperature field of the narrow strip spot of laser beam passing a scanning rotating mirror, the effect of scanning frequency on temperature field was analyzed in this study, and the math model of the temperature field with scanning frequency was derived applying the superposing principle of the temperature field. The value simulation and figures description were given. The relationship between scanning frequency and temperature distribution was studied, and the best extent of frequency was given for carbon steel laser quenching with laser rotating mirror. The value simulation shows that the higher the scanning frequency is, the more evenly distributed the temperature field gets. At a certain laser power and a certain length of laser scanning line spot, for non-melting laser heat treatment under the spot, a maximum thickness of the high- temperature layer can be get at some certain scanning frequency range which depends on thermal diffusion coefficient of the material.