scholarly journals Digital signal processsing functions for ultra-low frequency calibrations

ACTA IMEKO ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 374
Author(s):  
Henrik Ingerslev ◽  
Soren Andresen ◽  
Jacob Holm Winther
Keyword(s):  
Signal Processing ◽  
Low Frequency ◽  
Digital Signal ◽  
Low Noise ◽  
Key Comparison ◽  
Low Frequencies ◽  
Dual Channel ◽  
Ultra Low Noise ◽  
Lower Noise ◽  
Better Than

The demand from industry to produce accurate acceleration measurements down to ever lower frequencies and with ever lower noise is increasing. Different vibration transducers are used today for many different purposes within this area, like detection and warning for earthquakes, detection of nuclear testing, and monitoring of the environment. Accelerometers for such purposes must be calibrated in order to yield trustworthy results and provide traceability to the SI-system accordingly. For these calibrations to be feasible, suitable ultra low-noise accelerometers and/or signal processing functions are needed. <br />Here we present two digital signal processing (DSP) functions designed to measure ultra low-noise acceleration in calibration systems. The DSP functions use dual channel signal analysis on signals from two accelerometers measuring the same stimuli and use the coherence between the two signals to reduce noise. Simulations show that the two DSP functions are estimating calibration signals better than the standard analysis. <br />The results presented here are intended to be used in key comparison studies of accelerometer calibration systems, and may help extend current general low frequency range from e.g. 100 mHz down to ultra-low frequencies of around 10mHz, possibly using somewhat same instrumentation.

scholarly journals Study on the Technology of Ultra-high Sensitive Wide-band Magnetic-feedback Inductive Magnetic Sensor

2020 ◽  
Vol 327 ◽  
pp. 01002
Author(s):  
Yong Liu ◽  
Wenbin Li ◽  
Jinrong Zhou ◽  
Rui Pan ◽  
Huan Zheng ◽  
...  
Keyword(s):  
Wide Band ◽  
Low Noise ◽  
Magnetic Sensor ◽  
Core Material ◽  
Geological Exploration ◽  
High Impedance ◽  
Main Factors ◽  
Coil Winding ◽  
Ultra Low Noise ◽  
Better Than

It analyses the composition and principle of high-sensitive wide-band magnetic-feedback inductive magnetic sensor to fulfil the demand of high-sensitive wide-band magnetic sensor in geological exploration. It studies main factors to the performance of wide-band magnetic sensor, such as turns of coils, core material features, and amplifier noise, specifies section-wise coil winding, the type and dimension of core material, and designs low-noise high-impedance LF chopping amplifier channel and composite amplifier with HF amplifier channel. The noise of magnetic sensor at 1 Hz is better than 10-4nT/Hz1/2, at 100Hz-1kHz band the noise floor is close to SQUID which can reach 10-6nT/Hz1/2. The magnetic sensor works at wide frequency band (0.0001Hz-10kHz) and ultra-low noise, which can meet the requirements of both AMT and CSAMT.

An ultra-low-noise, low-frequency, six degrees of freedom active vibration isolator

1997 ◽  
Vol 68 (8) ◽  
pp. 3211-3219 ◽  
Author(s):  
D. B. Newell ◽  
S. J. Richman ◽  
P. G. Nelson ◽  
R. T. Stebbins ◽  
P. L. Bender ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Low Frequency ◽  
Low Noise ◽  
Vibration Isolator ◽  
Six Degrees Of Freedom ◽  
Active Vibration ◽  
Ultra Low Noise

scholarly journals Ultra-low noise HEMTs for high-impedance and low- frequency preamplifiers: realization and characterization from 4.2 K to 77 K

2014 ◽  
Vol 568 (3) ◽  
pp. 032009 ◽  
Author(s):  
Y Jin ◽  
Q Dong ◽  
Y X Liang ◽  
A Cavanna ◽  
U Gennser ◽  
...  
Keyword(s):  
Low Frequency ◽  
Low Noise ◽  
High Impedance ◽  
Ultra Low Noise

Low-frequency noise correlations in lateral pnp bipolar transistors

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1112-1117
Author(s):  
A. Nathan ◽  
E. Charbon ◽  
W. Kung ◽  
A. Salim
Keyword(s):  
Integrated Circuit ◽  
Low Frequency ◽  
Intrinsic Noise ◽  
Low Noise ◽  
Bipolar Transistors ◽  
Current Gain ◽  
Low Noise Amplifiers ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Low Frequencies

Measurement results of low-frequency noise behaviour, and in particular, the noise correlations in lateral pnp bipolar transistors are presented for various bias conditions in both forward active and saturation regimes. The correlation in output collector noise is very high with a value close to unity only when the device is in medium injection. At extremely high injection, the degree of coherence degrades, depicting a behaviour similar to the forward current gain of the device. This degradation can be attributed to emitter-crowding effects. The correlation in output noise can be exploited to drastically suppress the intrinsic noise, particularly at low frequencies, making such devices useful for the input stage of amplifiers; the first step towards realisation of ultra low-noise amplifiers in standard integrated circuit technology.

scholarly journals Very low-frequency IEPE accelerometer calibration and application to a wind energy structure

2021 ◽  
Author(s):  
Clemens Jonscher ◽  
Benedikt Hofmeister ◽  
Tanja Grießmann ◽  
Raimund Rolfes
Keyword(s):  
Measurement Data ◽  
Low Frequency ◽  
Calibration Procedure ◽  
Low Noise ◽  
Energy Structure ◽  
Frequency Range ◽  
Low Frequencies ◽  
Iir Filters ◽  
Very Low Frequency ◽  
Ac Response

Abstract. In this work, we present an experimental setup for very low-frequency calibration measurements of low-noise Integrated Electronics Piezo Electric (IEPE) accelerometers and a customised signal conditioner design for using IEPE sensor down to 0.05Hz. AC-response IEPE accelerometer and signal conditioners have amplitude and phase deviations at low frequencies. As the standard calibration procedure in the low-frequency range is technically challenging, IEPE accelerometers with standard signal conditioners are usually used in frequency ranges above 1 Hz. Vibrations on structures with low eigenfrequencies like wind turbines are thus often monitored using DC-coupled micro-electro-mechanical systems (MEMS) capacitive accelerometers. This sensor type suffers from higher noise levels compared to IEPE sensors. To apply IEPE sensors instead of MEMS sensors, in this work the calibration of the entire measurement chain of three different IEPE sensors with the customised signal conditioner is performed with a low-frequency centrifuge. The IEPE sensors are modelled using IIR filters to apply the calibration to time-domain measurement data of a wind turbine support structure. This procedure enables an amplitude and phase-accurate vibration analysis with IEPE sensors in the low-frequency range down to 0.05 Hz.

scholarly journals Experimental evidence for real-time song frequency shift in response to urban noise in a passerine bird

2010 ◽  
Vol 7 (1) ◽  
pp. 36-38 ◽  
Author(s):  
Eira Bermúdez-Cuamatzin ◽  
Alejandro A. Ríos-Chelén ◽  
Diego Gil ◽  
Constantino Macías Garcia
Keyword(s):  
Experimental Evidence ◽  
Signal Transmission ◽  
Low Frequency ◽  
Low Noise ◽  
Noise Levels ◽  
Short Term ◽  
Urban Noise ◽  
Low Frequencies ◽  
House Finches ◽  
Minimum Frequency

Research has shown that bird songs are modified in different ways to deal with urban noise and promote signal transmission through noisy environments. Urban noise is composed of low frequencies, thus the observation that songs have a higher minimum frequency in noisy places suggests this is a way of avoiding noise masking. Most studies are correlative and there is as yet little experimental evidence that this is a short-term mechanism owing to individual plasticity. Here we experimentally test if house finches ( Carpodacus mexicanus ) can modulate the minimum frequency of their songs in response to different noise levels. We exposed singing males to three continuous treatments: low–high–low noise levels. We found a significant increase in minimum frequency from low to high and a decrement from high to low treatments. We also found that this was mostly achieved by modifying the frequency of the same low-frequency syllable types used in the different treatments. When different low-frequency syllables were used, those sung during the noisy condition were longer than the ones sang during the quiet condition. We conclude that house finches modify their songs in several ways in response to urban noise, thus providing evidence of a short-term acoustic adaptation.

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