Novel inertial extremely low frequency transducer
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Abstract:
A seismic velocity transducer (SVT) is the commonly used pickup in engineering. However it is unsuitable for low frequency vibration measurement due to the limitation set by the mechanical natural frequency. It is showed that connecting a capacitor in parallel to the output terminal of SVT means the equivalent mass and damping coefficient are increased. The reliability and measurement range are increased and the natural frequency is lowered at the cost of the decrement of sensitivity at high frequency band. And the decrement of sensitivity of the pick up at low frequency band can not been visibly observed. A circuit network is used to further compensate the low frequency characteristics and a novel type of inertial extremely low frequency transducer is obtained.Keywords:
Natural frequency
Frequency band
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The inertial magnetoelectric velocity sensor is widely used in the fields of vibration control and measurement. The frequency response in the low frequency range is, however, limited by high frequency resonance because of the characteristic of second order high pass filter of the structure. A frequency-selected network for amplitude-frequency characteristic compensation to improve the performance of the frequency response is presented. The frequency-selected network, which is composed of amplifiers, resistors, and capacitances, is connected to the output port of the sensor in cascade without any modification of the sensor's structure. After compensation, the frequency band of the sensor is flattened and frequency response still has the characteristic of second order high pass filter, whereas the resonant frequency decreases from ~ 10 to 0.93 Hz. Meanwhile, it keeps the transducer in small size and light weight. The experimental results have shown that the sensor after been compensated has good performance in the low frequency range.
Frequency multiplier
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Frequency compensation
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The frequency response of a pressure transducer is influenced by the natural resonance of the sensor structure, the spatial resolution of the sensor due to its diaphragm size, the sensor packaging, signal conditioning and mounting at the measurement location. The resonance of the sensor and aerodynamically-driven resonances related to the sensor packaging and/or mounting, specifically, can distort dynamic pressure measurements within the range of greatest interest (10Hz–20kHz), typically resulting in erroneous amplification. Historically, correcting for such errors within the frequency response of a pressure transducer or measurement system has been challenging, because such errors are hard to quantify with unknown resonant frequencies and damping factors (quality factors). However, with the ability to fully characterize resonant frequencies that lie within 10Hz–50kHz using a previously demonstrated dynamic pressure characterization methodology, it is possible to apply electrical filtering to substantially extend the flat (0±2dB) frequency response of a transducer before any digital signal conversion. In this work, we present a real-time frequency response compensation scheme that uses electrical filtering to correct for aerodynamically driven packaging or mounting related resonances while at the same time preventing signal distortion caused by the sensor resonances. The compensation extends the useable, flat amplitude bandwidth of the transducer while also correcting the phase response to maintain constant time delay over the extended bandwidth. This real-time frequency response correction scheme can be similarly used to compensate for chip resonances, which can limit the frequency response in applications such as shock and blast testing. A theoretical model of the frequency response correction methodology is presented. We additionally present temperature dependent experimental results that compare the frequency response with and without the correction scheme. These results demonstrate that the usable bandwidth of pressure transducers can be increased when real time, analog frequency response correction is applied. This work shows that if the frequency response of a transducer is well characterized, advanced signal conditioning can be implemented to substantially extend the flat bandwidth of the transducer without changes to the sensor, packaging or mounting.
SIGNAL (programming language)
Phase response
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A transducer of low mechanical and electrical inertia is described, whose voltage output is proportional to angular velocity. The device is without commutator and is not based on a modulation principle, so that it has a fast low-noise response. It operates through a rotation angle of up to 240 degrees, over which range a linearity of 1% or better is obtainable. There are no moving iron parts, so that the moment of inertia is effectively that of the drive shaft. The electrical time constant is about 50 ns when feeding into a resistance of 1 omega; the frequency response is thus in practice limited only by the mechanical characteristics of the device and its attachment to the object whose rotation is to be measured. A typical sensitivity, obtained by a fundamental method of calibration, is 30 mv for an angular velocity of 1 rad s-1. Some applications of the instrument are discussed. Including its use for measuring angular displacement.
Moment of inertia
Linearity
Commutator
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Feed forward
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Wheatstone bridge
Pressure measurement
Natural frequency
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Piezoresistive effect
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Thermistor
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The paper presents a development of the linear position transducer of variable-reluctance type, which has enlarged the operating velocity range without a deterioration in accuracy, in comparison with the earlier linear variable-reluctance transducer. An alternative magnetic circuit arrangement has been introduced to allow a substantial increase of excitation frequency with minimal detrimental effect on the output linearity. This, in turn, has enabled velocity-dependent dynamic error to be minimised, through a reduction of the phase shift between processed and actual amplitude envelopes of induced voltages, and by mitigating the undesirable impact of the velocity-dependent component of induced voltage on the output signal. The transducer's accuracy and sensitivity remain independent of the sensing range.
Magnetic reluctance
Linearity
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Position (finance)
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Frequency band
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Authors propose the use of an ultrasonic transducer to achieve a passive safety system for a collision using a corner sensor. However, the sensitivity of the transducer decreases owing to Doppler shift in the case of a travelling car. On the contrary, authors also propose a resonance control method for the transducer using a generalized impedance converter (GIC) circuit. In this study, the resonance control frequency method is used to correct the sensitivity of the transducer. In the sensitivity control, the input impedance control of the GIC circuit is tried using a voltage-controlled resistance. The automatic sensitivity correction control is expected to be realized by a combination of the GIC circuit and frequency–voltage (F/V) converter. As a result, the sensitivity of a Langevin transducer with a GIC circuit as a receiver is slightly improved, compared with that of a retailed transducer. Moreover, the resonance frequency of the transducer can be controlled in the range of about 3 kHz using the GIC circuit and F/V converter.
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