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In-Process Inspection System Using Tool-Touch Auditron
Published in Stephan D. Murphy, In-Process Measurement and Control, 2020
The sensor was evaluated in its ruggedized form using the printed circuit board design, as opposed to the earlier hand-wired versions. The acoustic emission transducer was a Dune-gan/Endevco D750. The specified compressional wave frequency bandwidth for this transducer is 100 to 300 kHz with a sensitivity of 60 db at its resonant peak frequency. The same transducer had been used in earlier feasibility testing at GE with the Gray VTL and other machines for both touch sensing and closed-loop machining. The amplifier was the same one used in earlier designs. The unit consists primarily of an active high-pass filter with thresholding and analog-to-digital conversion to provide an appropriate signal for the CNC controller. The updated printed circuit board version of the sensor made provisions for wire wrap selectable filtering. The filter’s high-pass cutoff frequency can be changed via a pad of two resistors and two capacitors. The amplifier gain is easily changed via a pad of four resistors. The amplifier accommodates both single-ended and differential acoustic emission sensors through wire wrap jumpers. The D750 transducer utilized provides a differential signal; thus the amplifier was configured accordingly for the evaluation.
Filters
Published in Afshin Samani, An Introduction to Signal Processing for Non-Engineers, 2019
What in practice one can achieve with frequency-based filters does not have a sharp and clear-cut frequency response as shown in Figure 8.1. There will always be a transition phase around the cut-off frequency. The cut-off frequency is often defined as a threshold where the power of the output signal drops to half of the power of components with no attenuation (Widmann, Schröger, and Maess, 2015) (often where the magnitude of the frequency response is 1, the filter does not attenuate the frequency components in that range). I already stated that the power spectrum of the output is proportional to the square of the magnitude of the system frequency response, and therefore, the cut-off frequency is the frequency limit where the magnitude of the frequency response drops to 12 of its magnitude when no attenuation is applied (often where the magnitude is 1).
Measurement Systems: Other Components
Published in Patrick F. Dunn, Michael P. Davis, Measurement and Data Analysis for Engineering and Science, 2017
Patrick F. Dunn, Michael P. Davis
The most common types of ideal filters are presented in Figure 7.6. The term ideal implies that the magnitude of the signal passing through the filter is not attenuated over the desired band of frequencies. The term band refers to a range of frequencies and the term pass denotes the unaltered passing. The range of frequencies over which the signal is attenuated is called the stop-band. The low-pass filter passes lower signal frequency content up to the cutoff frequency, fc, and the high-pass filter passes content above fc. A low-pass filter and high-pass filter can be combined to form either a band-pass filter or a notch filter, each having two cutoff frequencies, fcL and fcH. Actual filters do not have perfect step changes in amplitude at their cutoff frequencies. Rather, they experience a more gradual change, which is characterized by the roll-off at fc, specified in terms of the ratio of amplitude change to frequency change.
Study on the drop impact acceleration of the radioactive package by new approximation method based on velocity obtained by integrating acceleration
Published in Journal of Nuclear Science and Technology, 2023
Kenichi Hakozaki, Hiroaki Taniuchi, Shinichi Takahashi
In the drop test for Type B packages that comply with the IAEA Transport Regulations, it is necessary to ensure the safety of the package. Radioactive material leakage must not exceed the specified limits during and after the test [1,2]. The safety of the package is confirmed by structural analysis assessment that the integrity of the containment boundary is maintained after the drop test. To carry out an accurate structural analysis, it is necessary to determine the impact force acting on the package during the drop. Generally, a specimen simulating the package is used for the drop test, and the acceleration (deceleration) acting on the specimen under the drop test is measured by accelerometers installed on the specimen. In the drop test, the target of acceleration measurement is to find the deceleration time-series spectrum corresponding to the stopping force acting on the falling specimen owing to the drop impact against the floor. Because the accelerometer detects not only the target signal, but also various noises, to obtain the acceleration corresponding to the target stopping force. In previous studies, low-pass filtering was commonly applied to remove high-frequency noise components. For low-pass filtering it is necessary to determine the cutoff frequency.
Identifying Stick-Slip Characteristics of a Smart Device on a Seismically Excited Surface Using On-Board Sensors
Published in Journal of Earthquake Engineering, 2022
Yunsu Na, Sherif El-Tawil, Ahmed Ibrahim, Ahmed Eltawil
Experiments for earthquake motions as mentioned earlier are conducted to compare the denoising performance of three different methods: low-pass filter, MODWT, MODWPT. The low-pass filter is a filter that passes signals with a frequency lower than a selected cutoff frequency and attenuates signals with frequencies higher than the cutoff frequency. In this study, a 25 Hz cutoff frequency is selected based on the work of (Skolnik and Wallace 2010). For MODWT and MODWPT, the denoising procedure has three steps. The first step selects a wavelet and a level N and then computes the wavelet decomposition of the signals at level N. The second step pertains to coefficients thresholding, i.e. it selects a threshold and applies soft thresholding to the detail coefficients for each level from 1 to N. The third step computes wavelet reconstruction based on the original approximation coefficients of level N and the modified detail coefficients of levels 1 through N. Details can be found in Donoho (1995). In this study, ‘db 1ʹ wavelet and level 3 are selected empirically.
VHF high-power tunable low-pass filter based on nested coupled helical inductor
Published in International Journal of Electronics, 2021
Zhengwei Huang, Yong Cheng, Yuanjian Liu
The circuit principle of the proposed VHF tunable low-pass filter based on a set of nested coupled spiral inductors in section 2.1 is shown in Figure 1(c), which includes a set of nested coupled helical inductors and a variable capacitor. A set of nested coupled helical inductors can be considered as two coupling inductors of the homonymous terminal. According to the decoupling theory of coupled inductance T-type circuit (William et al., 2011), the proposed circuit can be equivalent to a third-order low-pass filter with a transmission zero, as shown in Figure 1(d), in which M represents the mutual inductance of L1 and L2. By changing the value of capacitor Cp, the cut-off frequency and transmission zero of the low-pass filter can be adjusted. According to the design theory of m-derived filter based on the image parameter method (David, 2011), the m-derived filter is composed of m-derived T-shaped low-pass filter sections to provide the desired cut-off frequency and attenuation characteristics. The following equation can be obtained: