scholarly journals Compact Current Reference Circuits with Low Temperature Drift and High Compliance Voltage

Sensors ◽  
2020 ◽  
Vol 20 (15) ◽  
pp. 4180
Author(s):  
Sara Pettinato ◽  
Andrea Orsini ◽  
Stefano Salvatori
Keyword(s):  
Calibration Procedure ◽  
Passive Component ◽  
Thermal Coefficient ◽  
Active Components ◽  
Temperature Drift ◽  
Active Sensors ◽  
Output Resistance ◽  
Resistive Sensor ◽  
Interface Circuitry ◽  
Display Performance

Highly accurate and stable current references are especially required for resistive-sensor conditioning. The solutions typically adopted in using resistors and op-amps/transistors display performance mainly limited by resistors accuracy and active components non-linearities. In this work, excellent characteristics of LT199x selectable gain amplifiers are exploited to precisely divide an input current. Supplied with a 100 µA reference IC, the divider is able to exactly source either a ~1 µA or a ~0.1 µA current. Moreover, the proposed solution allows to generate a different value for the output current by modifying only some connections without requiring the use of additional components. Experimental results show that the compliance voltage of the generator is close to the power supply limits, with an equivalent output resistance of about 100 GΩ, while the thermal coefficient is less than 10 ppm/°C between 10 and 40 °C. Circuit architecture also guarantees physical separation of current carrying electrodes from voltage sensing ones, thus simplifying front-end sensor-interface circuitry. Emulating a resistive-sensor in the 10 kΩ–100 MΩ range, an excellent linearity is found with a relative error within ±0.1% after a preliminary calibration procedure. Further advantage is that compliance voltage can be opposite in sign of that obtained with a passive component; therefore, the system is also suitable for conditioning active sensors.

Boron uptake by the root cortex symplast of tomato and pea plants: evidence for low-boron-induced active transport

2007 ◽  
Vol 34 (12) ◽  
pp. 1130 ◽  
Author(s):  
Jasna Savic ◽  
Miroslav Nikolic ◽  
Slaven Prodanovic ◽  
Volker Römheld
Keyword(s):  
Time Course ◽  
Active Component ◽  
Metabolic Energy ◽  
Passive Component ◽  
Uptake System ◽  
Boron Uptake ◽  
Active Components ◽  
Cortical Cells ◽  
Root Cortex ◽  
B Uptake

The objective of this research was to test the hypothesis of the existence of an active boron (B) uptake into the cortical cells induced by low B supply. The uptake of B was characterised in two tomato (Lycopersicon esculentum Mill.) genotypes: B-efficient FER and B-inefficient mutant T3238. In addition, pea (Pisum sativum L.) was used as an anatomically appropriate model for obtaining intact root cortex. Time course uptake studies in tomato indicate that the B-inefficient mutant was defective by the absence of an active low-B-induced uptake system in the cortex. Pea roots showed up to 10-fold higher accumulation of B into the cortex symplast at low (0.5 µm) external B supply in comparison to adequate B (10 µm) supply. Also, low-B-induced uptake of B was strongly inhibited by 2,4-dinitrophenol, indicating a metabolic energy-derived active component of B uptake at low external supply. Uptake of B by the cortical cells of tomato and pea plants appears to be a combination of both passive and active components, with a passive component prevailing at higher external B. An active component of B uptake suppressed by either adequate or high B supply might indicate a downregulation of plasma membrane-associated B transporter(s) in root cortical cells.

Embedded Self-Sensing Piezoelectric Active Sensors for On-Line Structural Identification

2001 ◽  
Vol 124 (1) ◽  
pp. 116-125 ◽  
Author(s):  
Victor Giurgiutiu ◽  
Andrei N. Zagrai
Keyword(s):  
Mechanical Response ◽  
Impedance Spectrum ◽  
Structural Identification ◽  
Calibration Procedure ◽  
Structural Vibration ◽  
Sensor Calibration ◽  
Ultrasonic Frequency ◽  
Active Sensors ◽  
Turbine Engine ◽  
On Line

The benefits and limitations of using embedded piezoelectric active sensors for structural identification at ultrasonic frequency are highlighted. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electro-mechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimension structures and accounts for both axial and flexural vibrations. Experiments were conducted on simple specimens in support of the theoretical investigation, and on realistic turbine blade specimen to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the latter’s noninvasive characteristics. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a nonintrusive sensor array adequate for on-line automatic structural identification and health monitoring. The sensor calibration procedure is outlined. Numerical estimation of the noninvasive properties of the proposed active sensors in comparison with conventional sensors is presented. Self-diagnostics capabilities of the proposed sensors were also investigated and methods for automatic self-test implementation are discussed. The paper underlines that the use of piezoelectric wafer active sensors is not only advantageous, but, in certain situations, may be the sole investigative option, as in the case of precision machinery, small but critical turbine-engine parts, and computer industry components.

scholarly journals Characterization of Piezoelectric Wafer Active Sensors

2000 ◽  
Vol 11 (12) ◽  
pp. 959-976 ◽  
Author(s):  
Victor Giurgiutiu ◽  
Andrei N. Zagrai
Keyword(s):  
Mechanical Response ◽  
Impedance Spectrum ◽  
Calibration Procedure ◽  
Structural Vibration ◽  
Sensor Calibration ◽  
Active Sensors ◽  
One Dimensional ◽  
Active Sensor ◽  
Aluminum Plates ◽  
In The Beginning

In the beginning, the classical one-dimensional analysis of piezoelectric active sensors is reviewed. The complete derivation for a free-free sensor is then extended to cover the cases of clamped and elastically constrained sensors. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electromechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimensional structures and accounts for both axial and flexural vibrations. The numerical analysis was performed and supported by experimental results. Experiments were conducted on simple beam specimens to support the theoretical investigation, and on thin gauge aluminum plates to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure is not modified by the presence of the sensor, thus validating the sensor’s non-invasive characteristics. The sensor calibration procedure is outlined and statistical analysis was presented. It was found that PZT active sensors have stable and repeatable characteristics not only in as-received condition, but also while mounted on 1-D or 2-D host structure. It is shown that such sensors, of negligible mass, can be permanently applied to the structure creating a non-intrusive sensor array adequate for on-line automatic structural identification and health monitoring.

Nonlinear Passive Elements Using Cam-Based Springs for Powered Robotic Ankles

2013 ◽  
Author(s):  
Jonathan Realmuto ◽  
Glenn Klute ◽  
Santosh Devasia
Keyword(s):  
Nonlinear Response ◽  
Active Component ◽  
Input Current ◽  
Passive Component ◽  
Active Components ◽  
Passive Element ◽  
Design Flexibility ◽  
Cam Profile ◽  
Current Systems ◽  
Elastic Elements

There is increasing interest in powered prosthesis. To reduce energy, power, and torque requirements on the active input, current systems, such as powered ankle prosthetics, utilize a combination of passive and active components. By storing and releasing energy during gait, the passive component reduces the energy/power/torque requirements of the active component. Therefore, it is advantageous to maximize the use of the passive component for achieving the desired motion. Typically, the passive component utilizes elastic elements such as springs, which cannot be easily adjusted to achieve a desired optimal nonlinear response. In this work, we report the use of a cam profile to achieve a general desired nonlinear response. The results show that the added design flexibility (to achieve nonlinear response of the passive element) can substantially reduce the energy/power/torque requirement of the active component.

scholarly journals Some New First-Order All-Pass Realizations Using CCII

2004 ◽  
Vol 27 (2) ◽  
pp. 91-94 ◽  
Author(s):  
Kirat Pal ◽  
Seema Rana
Keyword(s):  
Input Impedance ◽  
Second Generation ◽  
Current Conveyor ◽  
The Other ◽  
Passive Component ◽  
Current Conveyors ◽  
High Input ◽  
Active Components ◽  
High Input Impedance ◽  
First Order

Some new first-order all-pass filters using a second-generation current conveyor are reported. Two circuits have higher input impedance than reported very recently and use a grounded capacitor. Additionally two more circuits have been reported, one of which has minimum passive and active components and has the facility of single resistance tuning. The other circuit has high input impedance and uses two current conveyors but has one passive component less than the similar circuits reported earlier.

scholarly journals Magnetic Resonance Compatible Knee Extension Ergometer

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Youssef Jaber ◽  
Ericber Jimenez Francisco ◽  
Miles F. Bartlett ◽  
Liam F. Fitzgerald ◽  
Jane A. Kent ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Resonance ◽  
Mechanical Performance ◽  
Knee Extension ◽  
Metabolic Energy ◽  
Passive Component ◽  
Active Components ◽  
Lower Limb Muscles ◽  
Main Challenge ◽  
Adjacent Room

Abstract A magnetic resonance (MR) compatible ergometer has been developed to study contracting lower limb muscles during acquisition of MR spectroscopy data, a technique to noninvasively measure metabolic energy in muscle tissue. Current active and passive MR-compatible ergometer designs lack torque or velocity control to allow precise mechanical measurements during isotonic and isokinetic contractions; incorporating load and velocity controllers while maintaining MR-compatibility is the main challenge. Presented in this paper is the design and evaluation of an MR-compatible ergometer designed to control knee torque or velocity up to 420 N·m and 270 deg/s and is able to operate in a 3 Tesla magnetic field. The ergometer comprising of a passive component with no electronics or ferrous materials is located inside the bore of the scanner. The active component with the electronics and actuator located outside of the magnetic field in an adjacent room. The active components connect to the passive components via a cable that passes through the waveguide, a hole in the wall of the scanner room. System evaluations were performed and human subject evaluations were performed that measured the mechanical performance and show the mean percent errors below 9% in isotonic and 2% in isokinetic conditions.

Active components isolated from Trapa natants increase glucose uptake in C2C12 myotubes

Planta Medica ◽  
2016 ◽  
Vol 81 (S 01) ◽  
pp. S1-S381
Author(s):  
HC Huang ◽  
CL Chao ◽  
SY Hwang ◽  
TC Chang ◽  
CH Chao ◽  
...  
Keyword(s):  
Glucose Uptake ◽  
C2c12 Myotubes ◽  
Active Components ◽  
Increase Glucose Uptake

Optical analysis of ink and other contaminants in process waters

TAPPI Journal ◽  
2012 ◽  
Vol 11 (8) ◽  
pp. 51-58
Author(s):  
ANTTI HAAPALA ◽  
MIKA KÖRKKÖ ◽  
ELISA KOIVURANTA ◽  
JOUKO NIINIMÄKI
Keyword(s):  
Optically Active ◽  
Process Water ◽  
Paper Machine ◽  
Optical Analysis ◽  
Direct Process ◽  
Active Components ◽  
Water Contaminants ◽  
Dependent Measurement ◽  
Measurement Methodology

Analysis methods developed specifically to determine the presence of ink and other optically active components in paper machine white waters or other process effluents are not available. It is generally more interest¬ing to quantify the effect of circulation water contaminants on end products. This study compares optical techniques to quantify the dirt in process water by two methods for test media preparation and measurement: direct process water filtration on a membrane foil and low-grammage sheet formation. The results show that ink content values obtained from various analyses cannot be directly compared because of fundamental issues involving test media preparation and the varied methodologies used to formulate the results, which may be based on different sets of assumptions. The use of brightness, luminosity, and reflectance and the role of scattering measurements as a part of ink content analysis are discussed, along with fine materials retention and measurement media selection. The study concludes with practical tips for case-dependent measurement methodology selection.

Catalysts for hydrogenation of CO2 into components of motor fuels

2020 ◽  
pp. 1-18
Author(s):  
Yu.V. Bilokopytov ◽  
◽  
S.L. Melnykova ◽  
N.Yu. Khimach ◽  
◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Heterogeneous Catalysts ◽  
Fossil Fuels ◽  
Catalyst Stability ◽  
Co2 Conversion ◽  
Active Components ◽  
Synthesis Conditions ◽  
Hydrogenation Of Co2 ◽  
Mesoporous Zeolites ◽  
Motor Fuels

CO2 is a harmful greenhouse gas, a product of chemical emissions, the combustion of fossil fuels and car exhausts, and it is a widely available source of carbon. The review considers various ways of hydrogenation of carbon dioxide into components of motor fuels - methanol, dimethyl ether, ethanol, hydrocarbons - in the presence of heterogeneous catalysts. At each route of conversion of CO2 (into oxygenates or hydrocarbons) the first stage is the formation of CO by the reverse water gas shift (rWGS) reaction, which must be taken into account when catalysts of process are choosing. The influence of chemical nature, specific surface area, particle size and interaction between catalyst components, as well as the method of its production on the CO2 conversion processes is analyzed. It is noted that the main active components of CO2 conversion into methanol are copper atoms and ions which interact with the oxide components of the catalyst. There is a positive effect of other metals oxides additives with strong basic centers on the surface on the activity of the traditional copper-zinc-aluminum oxide catalyst for the synthesis of methanol from the synthesis gas. The most active catalysts for the synthesis of DME from CO2 and H2 are bifunctional. These catalysts contain both a methanol synthesis catalyst and a dehydrating component, such as mesoporous zeolites with acid centers of weak and medium strength, evenly distributed on the surface. The synthesis of gasoline hydrocarbons (≥ C5) is carried out through the formation of CO or CH3OH and DME as intermediates on multifunctional catalysts, which also contain zeolites. Hydrogenation of CO2 into ethanol can be considered as an alternative to the synthesis of ethanol through the hydration of ethylene. High activation energy of carbon dioxide, harsh synthesis conditions as well as high selectivity for hydrocarbons, in particular methane remains the main problems. Further increase of selectivity and efficiency of carbon dioxide hydrogenation processes involves the use of nanocatalysts taking into account the mechanism of CO2 conversion reactions, development of methods for removing excess water as a by-product from the reaction zone and increasing catalyst stability over time.

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