Frequency Response Characterization for Dynamic Measurement of Pressure

2019 ◽  
Author(s):  
George Papadopoulos ◽  
Daniel Bivolaru
Keyword(s):  
Frequency Response ◽  
Dynamic Pressure ◽  
Harsh Environments ◽  
Measured Signal ◽  
Sensing Element ◽  
Optimum Frequency ◽  
Size Constraints ◽  
Dynamic Pressure Measurements ◽  
Point Level ◽  
Transducer Frequency

Abstract Transducer requirements for making true dynamic pressure measurements point to a miniature point-level sensing element that is exposed to the flow. Meeting this requirement, however, is often challenged by transducer size constraints, integration at the location of measurement, and packaging, especially when one considers applications in harsh environments where protection of the sensing element may be needed. As part of an effort towards the development of a high frequency pressure measurement device for use in harsh environments (ultra-high temperature), an investigation was performed to evaluate the effect of sensing element packaging and geometry at the point of measurement on the dynamic response of a nominal transducer. Frequency and time domain calculations were performed to assess variations on the magnitude and phase between an input signal and a “measured” signal at the sensing element location for a range of probe tip parameters. The results offer insights and metrics that can govern transducer sensing element and probe tip implementation for optimum frequency response and strategies for compensation.

An Experimental and Theoretical Investigation of Wave Propagation in Teflon and Nylon Tubing With Methods to Prevent Aliasing in Pressure Scanners

2013 ◽  
Author(s):  
Adam M. Hurst ◽  
Joe VanDeWeert
Keyword(s):  
Frequency Response ◽  
Dynamic Pressure ◽  
Sampling Rate ◽  
Aircraft Design ◽  
Experimental Results ◽  
Analytical Models ◽  
Pressure Measurements ◽  
Pressure Transmission ◽  
Dynamic Pressure Measurements ◽  
Nylon Tubing

Accurate static and dynamic pressure measurements provide the feedback needed to advance gas turbine efficiency and reliability as well as improve aircraft design and flight control. During turbine testing and aircraft flight testing, flush mounting pressure transducers at the desired pressure measurement location is not always feasible and recess mounting with connective tubing is often used as an alternative. Resonances in the connective tubing can result in aliasing within pressure scanners even within a narrow bandwidth and especially when higher frequency content DC to ∼125Hz is desired. We present experimental results that investigate tube resonances and attenuation in 1.35mm inner diameter (ID) (used on 0.063in tubulations) and 2.69mm ID (used on 0.125in tubulations) Teflon and Nylon tubing at various lengths. We utilize a novel dynamic pressure generator, capable of creating large changes in air pressure (<1psi to 10psi, <6.8kPa to 68.9kPa), to determine the frequency response of such tubing from ∼1Hz to 2,800Hz. We further compare these experimental results to established analytical models for propagation of pressure disturbances in narrow tubes. While significant theoretical and experimental work relating to the frequency response of connective tubing or transmission lines has been published, there is limited literature presenting experimental frequency response data with air as the media in elastic tubing. In addition, little progress has been made in addressing the issue of tubing-related aliasing within pressure scanners, as the low sampling rate in scanners often makes post-processing antialiasing filters ineffective. The experimental results and analytical models presented herein can be used as a guideline to prevent aliasing and signal distortion by guiding the proper design of pressure transmission systems, resulting in accurate static and dynamic pressure measurements with pressure scanners. The data presented here should serve as a reference to instrumentation engineers so that they can make higher frequency measurements (up to ∼125Hz, currently) and are able to quantify the expected pressure transmission line (tube) attenuation and know if aliasing will be a concern. This information will give engineers greater measurement capability when using pressure scanners to make static and dynamic pressure measurements.

An Experimental Frequency Response Characterization of MEMS Piezoresistive Pressure Transducers

2014 ◽  
Author(s):  
Adam M. Hurst ◽  
Timothy R. Olsen ◽  
Scott Goodman ◽  
Joe VanDeWeert ◽  
Tonghuo Shang
Keyword(s):  
Transfer Function ◽  
Shock Tube ◽  
Frequency Response ◽  
Microelectromechanical Systems ◽  
Dynamic Pressure ◽  
Measured Signal ◽  
Test Setup ◽  
Pressure Transducers ◽  
Sensor Structure ◽  
Natural Resonance

Silicon micro-machined piezoresistive based pressure transducers are often used to make high frequency dynamic pressure measurements. The spectral or frequency response of these microelectromechanical systems (MEMS) is a function of the natural resonance of the sensor structure, sensor size, sensor packaging, signal conditioning and transducer mounting in the desired measurement location. The advancement of MEMS micro-fabrication, which has reduced sensor size dramatically, and the high elastic modulus of silicon have allowed the natural resonance of these devices to range from 100kHz to several MHz [1]. As a result, packaging and mounting at the point of measurement are the major factors that determine the flat (0dB) frequency response envelope of the transducer, which is typically quantified by a transfer function. The transfer function quantifies the difference both in magnitude and phase between an input signal and a measured signal in the frequency domain. The dynamic response of pressure transducers has historically been estimated via a unit step input in pressure created through a shock tube test that excites the high natural resonance of the chip. Unfortunately, these tests are less effective at accurately quantifying the frequency response of the transducer in the domain of greatest interest (DC-20kHz), specifically the bandwidth over which the response is flat (0dB). In this work, we present a test methodology using a speaker-driven dynamic pressure calibration setup for experimentally determining the transfer function of a pressure transducer from 1–50kHz. The test setup is validated using capacitive-based microphones with claimed flat spectral characteristics well beyond 50kHz. Using this test setup, we present experimental spectral response results for low-pressure miniature MEMS piezoresistive pressure transducers over the frequency range of 1–50kHz and qualitatively compare these results to traditional shock tube tests. The transducers characterized have been manufactured with several different standard sizes and front-end configurations.

A Study of Bulk Modulus, Entrained Air, and Dynamic Pressure Measurements in Liquids

2016 ◽  
Vol 138 (10) ◽  
Author(s):  
Adam M. Hurst ◽  
Joe VanDeWeert
Keyword(s):  
Bulk Modulus ◽  
Frequency Response ◽  
Measurement System ◽  
Pressure Transducer ◽  
Dynamic Pressure ◽  
Pressure Measurements ◽  
Liquid Media ◽  
Pressure Transducers ◽  
Dynamic Pressure Measurements ◽  
Dissolved Air

Accurate static and dynamic pressure measurements in liquids, such as fuel, oil, and hydraulic fluid, are critical to the control and health monitoring of turbomachinery and aerospace systems. This work presents a theoretical and experimental study of the frequency response of pressure transducers and pressure measurement systems in liquid media. First, we theoretically predict the frequency response of pressure transducers based upon a lumped-parameter model. We then present a liquid-based dynamic pressure calibration test apparatus that validates this model by performing several critical measurements. This system first uses a vibrating liquid column to dynamically calibrate and experimentally determine the frequency response of a test pressure transducer, measurement system or geometry. Second, this calibration system experimentally extracts the bulk modulus of the fluid and the percent of entrained and/or dissolved air by volume. Bulk modulus is determined by measuring the speed of sound within the liquid and through static pressure loading while measuring the deflection of the liquid column. Bulk modulus and the entrained/dissolved gas content within the liquid greatly impact the observed frequency response of a pressure transducer or geometry. Gases, such as air, mixed or dissolved into a fluid can add substantial damping to the dynamic response of the fluid measurement system, which makes measurement of the bulk modulus and entrained and/or dissolved air critical for accurate measurement of the frequency response of a system when operating with a liquid media. All experimental results are compared to theoretical predictions.

scholarly journals Reproducibility of C. I. P.-compatible dynamic pressure measurements

2020 ◽  
Vol 87 (10) ◽  
pp. 630-636
Author(s):  
Oliver Slanina ◽  
Susanne Quabis ◽  
Robert Wynands
Keyword(s):  
Dynamic Pressure ◽  
Storage Conditions ◽  
Dynamic Measurement ◽  
Gas Pressure ◽  
Pressure Measurements ◽  
Small Arms ◽  
Minimum Pressure ◽  
Maximum Value ◽  
Preliminary Study ◽  
Dynamic Pressure Measurements

AbstractTo ensure the safety of users like hunters and sports shooters, the dynamic pressure inside an ammunition cartridge must not exceed a maximum value. We have investigated the reproducibility of the dynamic measurement of the gas pressure inside civilian ammunition cartridges during firing, when following the rules formulated by the Permanent International Commission for the Proof of Small Arms (C. I. P.). We find an in-house spread of 0.8 % between maximum and minimum pressure for runs with the same barrel and of 1.8 % among a set of three barrels. This sets a baseline for the expected agreement in measurement comparisons between different laboratories. Furthermore, a difference of more than 3 % is found in a preliminary study of the influence of ammunition storage conditions.

Application of side-hole fibers for dynamic pressure measurements

2000 ◽  
Author(s):  
Wojtek J. Bock ◽  
Magdalena S. Nawrocka ◽  
Waclaw Urbanczyk
Keyword(s):  
Dynamic Pressure ◽  
Pressure Measurements ◽  
Side Hole ◽  
Dynamic Pressure Measurements

Design of composite laminates for optimum frequency response

2012 ◽  
Vol 331 (8) ◽  
pp. 1759-1776 ◽  
Author(s):  
Rengin Kayikci ◽  
Fazil O. Sonmez
Keyword(s):  
Frequency Response ◽  
Composite Laminates ◽  
Optimum Frequency

Distribution of Flow Across the Radius of an Axisymmetric Shock Tube With Variable Cross-Sectional Area

1991 ◽  
Author(s):  
Stephen J. Schraml ◽  
Richard J. Pearson
Keyword(s):  
Shock Tube ◽  
Dynamic Pressure ◽  
Computer Code ◽  
Turbulence Modelling ◽  
Variable Cross ◽  
Cross Sectional ◽  
Flow Simulations ◽  
First Order ◽  
Series Of Experiments ◽  
Dynamic Pressure Measurements

Abstract Experiments were conducted to study the characteristics of unsteady flow in a small, axisymmetric shock tube. These experiments have been supplemented by calculational results obtained from the SHARC hydrodynamic computer code. Early calculational results indicated that a substantial gradient in flow velocity and dynamic pressure may exist along the cross-section of the shock tube. To further investigate this phenomenon, a series of experiments was performed in which dynamic pressure measurements were made at various radii in the expansion section of the shock tube. Additional calculations with the SHARC code were also performed in which turbulence modelling, artificial viscosity and second order advection were employed. The second set of calculations agree very well with the experimental results. These results indicate that the dynamic pressure is nearly constant across the radius of the shock tube. This contradicts the early computational results which were performed with first order advection and without turbulence modelling. As a result of these findings, it was concluded that turbulence modelling was necessary to obtain accurate shock tube flow simulations.

Measurements of Multiple Pure Tone Propagation From a High Bypass Turbofan Rotor in an Internal Flow Facility

2020 ◽  
Author(s):  
Richard F. Bozak
Keyword(s):  
Pure Tone ◽  
Dynamic Pressure ◽  
Pressure Ratio ◽  
Internal Flow ◽  
Principal Component ◽  
Pressure Transducers ◽  
Acoustic Liners ◽  
Pure Tones ◽  
Dynamic Pressure Measurements ◽  
Stagger Angle

Abstract An important noise source in modern high bypass ratio turbofans is from multiple pure tones produced by the fan during takeoff. An experiment conducted on a 1.5 pressure ratio fan in an internal flow facility provided dynamic pressure measurements to investigate multiple pure tone generation and propagation. Since multiple pure tones are generated by blade shock variation primarily due to the fan’s blade stagger angle differences, the blade stagger angles were measured with an array of over-the-rotor dynamic pressure transducers. Multiple pure tone measurements were made with 30 wall-mounted dynamic pressure transducers from 0.4 to 1.1 diameters upstream of the rotor. Measured blade stagger angle differences correspond to the the shock amplitude variation measured upstream. The acoustic field was extracted from the dynamic pressure signals using principal component analysis as well as duct mode beamforming. Shocks traveling out the inlet were found to couple to duct modes propagating at similar angles. Over-the-rotor acoustic liners appear to reduce rotor shock variation resulting in a reduction of sub-harmonic multiple pure tone sound pressure levels by 3–4 dB.

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