Wireless Passive Sensor for Remote pH Monitoring

2011 ◽  
Vol 2 (1) ◽  
Author(s):  
Sharmistha Bhadra ◽  
Greg E. Bridges ◽  
Douglas J. Thomson ◽  
Michael S. Freund
Keyword(s):  
Resonant Frequency ◽  
Response Time ◽  
Dynamic Range ◽  
Ph Monitoring ◽  
Ph Sensor ◽  
Sensor Technology ◽  
Biomedical Sensing ◽  
Voltage Dependent ◽  
Solution Changes

In this paper we describe a wireless passive pH sensor for high-resolution remote pH monitoring. The sensor is based on a passive LC coil resonator whose resonant frequency is monitored remotely by measuring the change in impedance of an interrogator coil coupled to the sensor coil. The sensor resonator consists of an inductive coil connected in parallel with a voltage dependent capacitor and a pH combination electrode. Change in the electrode potential in response to variations of the pH of the solution changes the capacitance, and therefore the resonant frequency of the sensor. A linear response with a 0.1 pH resolution is achieved over a 4–10 pH dynamic range. The response time of the sensor is demonstrated to be less than 30 s and is limited by the response time of the pH combination electrode. The described sensor technology is suitable for long-term remote pH monitoring in numerous fields such as biomedical sensing, environmental monitoring, industrial and chemical processing, and structural health monitoring.

scholarly journals Development and Application of the Single-Spiral Inductive-Capacitive Resonant Circuit Sensor for Wireless, Real-Time Characterization of Moisture in Sand

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Andrew J. DeRouin ◽  
Zhanping You ◽  
Morgan Hansen ◽  
Aboelkasim Diab ◽  
Keat Ghee Ong
Keyword(s):  
Resonant Frequency ◽  
Parasitic Capacitance ◽  
Sensor Technology ◽  
Resonant Circuit ◽  
Spiral Inductor ◽  
Road Pavement ◽  
Specific Frequency ◽  
Inductive Elements ◽  
Lc Sensors

A wireless, passive embedded sensor was designed and fabricated for monitoring moisture in sand. The sensor, consisted of an inductive-capacitive (LC) resonant circuit, was made of a printed spiral inductor embedded inside sand. When exposed to an electromagnetic field, the sensor resonated at a specific frequency dependent on the inductance of the inductor and its parasitic capacitance. Since the permittivity of water was much higher than dry sand, moisture in sample increased the parasitic capacitance, thus decreasing the sensor’s resonant frequency. Therefore, the internal moisture level of the sample could be easily measured through tracking the resonant frequency using a detection coil. The fabrication process of this sensor is much simpler compared to LC sensors that contain both capacitive and inductive elements, giving it an economical advantage. A study was conducted to investigate the drying rate of sand samples of different grain sizes. The experimental data showed a strong correlation with the actual moisture content in the samples. The described sensor technology can be applied for long term monitoring of localized water content inside soils and sands to understand the environmental health in these media, or monitoring moisture levels within concrete supports and road pavement.

scholarly journals Integrating Resonator to Enhance Magnetometer Microelectromechanical System Implementation with ASIC Compatible CMOS 0.18 μm Process

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 635
Author(s):  
Chih-Hsuan Lin ◽  
Chao-Hung Song ◽  
Kuei-Ann Wen
Keyword(s):  
Resonant Frequency ◽  
Tuning Range ◽  
Dynamic Range ◽  
Ambient Pressure ◽  
Readout Circuit ◽  
Microelectromechanical System ◽  
Correlated Double Sampling ◽  
Driving Current ◽  
Mems Oscillator ◽  
Oscillation Characteristics

In this study, a multi-function microelectromechanical system (MEMS) was integrated with a MEMS oscillator, using the resonant frequency oscillation characteristics of the oscillator to provide the Lorentz current of the magnetometer to enhance a large dynamic range of reading, which eliminates the off-chip clock and current generator. The resonant frequency can be adjusted by adjusting the bias voltage of the oscillator to further adjust the sensitivity of the magnetometer. With the mechanical Q value characteristic, a great dynamic range can be achieved. In addition, using the readout circuit of the nested chopper and correlated double-sampling (CDS) to reduce the noise and achieve a smaller resolution, the calibration circuit compensates for errors caused by the manufacturing process. The frequency of the tuning range of the proposed structure is 17,720–19,924 Hz, and the tuning range of the measurement result is 110,620.36 ppm. The sensitivities of the x-, y-, and z-axes of the magnetometer with driving current of 2 mA are 218.3, 74.33, and 7.5 μV/μT for ambient pressure of 760 torr. The resolutions of the x-, y-, and z-axes of the magnetometer with driving current of 2 mA are 3.302, 9.69, and 96 nT/√Hz for ambient pressure of 760 torr.

Genetically Engineered Pores as Metal Ion Biosensors

1993 ◽  
Vol 330 ◽  
Author(s):  
John Kasianowicz ◽  
Barbara Walker ◽  
Musti Krishnasastry ◽  
Hagan Bayley
Keyword(s):  
Response Time ◽  
Lipid Bilayers ◽  
Metal Ion ◽  
Dynamic Range ◽  
Divalent Cations ◽  
High Sensitivity ◽  
Genetically Engineered ◽  
Great Promise ◽  
Lipid Bilayer Membranes ◽  
Time Dynamic

ABSTRACTWe are adapting proteins that form pores in lipid bilayers for use as components of biosensors. Specifically, we have produced genetically engineered variants of the α hemolysin (αHL) fromStaphylococcusaureus with properties that are sensitive to low concentrations of divalent cations. For example, the pore-forming activity of one mutant (αHL-H5: residues 130–134 inclusive replaced with histidine) is inhibited by Zn2+at concentrations as low as 1 μM, as judged by the reduction in its ability to lyse rabbit red blood cells and to increase the conductance of planar lipid bilayer membranes. When αHL-H5 is added to the aqueous phase bathing one side of a planar membrane, the subsequent addition of 100 μM Zn2+to either side blocks the pores that form. This result suggests that at least part of the mutated region lines the channel lumen. Ca2+and Mg2+do not block the channel and therefore the H5 mutation confers a degree of analyte specificity to the αHL pore. The results suggest that genetically engineered pores have great promise for the rapid and sensitive detection of metal cations and we discuss the merits and potential limitations for their use in this application. Specifically, we examine the issues of selectivity, sensitivity, response time, dynamic range and longevity. Some of these properties are interdependent. For example, the goals of high sensitivity and rapid response time can be in conflict.

scholarly journals An Optical Fiber Sensor Based on La2O2S:Eu Scintillator for Detecting Ultraviolet Radiation in Real-Time

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3754 ◽  
Author(s):  
Yongji Yan ◽  
Xu Zhang ◽  
Haopeng Li ◽  
Yu Ma ◽  
Tianci Xie ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Response Time ◽  
Electromagnetic Interference ◽  
Uv Light ◽  
Optical Fiber Sensor ◽  
Temperature Response ◽  
Superior Performance ◽  
Fiber Sensor ◽  
Uv Detectors

A novel ultraviolet (UV) optical fiber sensor (UVOFS) based on the scintillating material La2O2S:Eu has been designed, tested, and its performance compared with other scintillating materials and other conventional UV detectors. The UVOFS is based on PMMA (polymethyl methacrylate) optical fiber which includes a scintillating material. Scintillating materials provide a unique opportunity to measure UV light intensity even in the presence of strong electromagnetic interference. Five scintillating materials were compared in order to select the most appropriate one for the UVOFS. The characteristics of the sensor are reported, including a highly linear response to radiation intensity, reproducibility, temperature response, and response time (to pulsed light) based on emission from a UV source (UV fluorescence tube) centered on a wavelength of 308 nm. A direct comparison with the commercially available semiconductor-based UV sensor proves the UVOFS of this investigation shows superior performance in terms of accuracy, long-term reliability, response time and linearity.

scholarly journals Ruthenium Oxide pH Sensing for Organs-On-Chip Studies

Proceedings ◽  
2018 ◽  
Vol 2 (13) ◽  
pp. 709 ◽  
Author(s):  
Esther Tanumihardja ◽  
Wouter Olthuis ◽  
Albert van den Berg
Keyword(s):  
Ph Sensor ◽  
Ruthenium Oxide ◽  
Open Circuit ◽  
Biological Medium ◽  
Similar Response ◽  
Ph Sensing ◽  
Ph Sensors ◽  
Cross Sensitivity ◽  
On Chip

A ruthenium oxide (RuOx) electrode is being developed as potentiometric pH sensor for organs-on-chip applications. Open-circuit potential (OCP) of the RuOx electrode showed a response of −58.05 mV/pH, with no cross-sensitivity to potentially interfering/complexing ions (tested were lithium, sulfate, chloride, and calcium ions). Similar response was observed in complex biological medium. The electrode stored in liquid had a long-term drift of −0.8 mV/hour (corresponding to ΔpH of 0.013/hour) and response time in complex biological medium was 3.7 s. Minimum cross-sensitivity to oxygen was observed as the OCP shifted ~3 mV going from deoxygenated to oxygenated solution. This response is one magnitude lower than previously reported for metal- oxide pH sensors. Overall, the RuOx pH sensor has proven to be a suitable pH sensor for organs- on-chip applications.

The Influence of Sign Variations on Drivers’ Comprehension

2018 ◽  
Vol 62 (1) ◽  
pp. 1918-1922
Author(s):  
Tamar Ben-Bassat ◽  
David Shinar
Keyword(s):  
Response Time ◽  
Long Term Memory ◽  
Background Color ◽  
Large Variability ◽  
Term Memory ◽  
Road Sign ◽  
Local Sign ◽  
Specific Sign ◽  
Non Local

Road Sign comprehension studies typically focus on differences among signs, demonstrating large variability in comprehension among different signs. Differences in features of sign design can be grouped into their shape, background color, and the symbol/icon in their center. This study demonstrated that specific sign messages can be presented with different sign features without detrimental effects on either comprehension level or response time. In particular, the choice of background color (yellow or white) appears to be inconsequential for comprehension. It seems that some sign characteristics are not critical to comprehension and consequently licensed drivers may even incorrectly identify a non-local sign as the standard sign that they actually encounter on the roads. However, other sign features – especially those relating to the icon/symbol - can be critical to comprehension when they violate the icon-concept compatibility, as it is represented in drivers' long-term memory.

scholarly journals Land subsidence and hydrodynamic compaction of sedimentary basins

1998 ◽  
Vol 2 (2/3) ◽  
pp. 159-171 ◽  
Author(s):  
H. Kooi ◽  
J. J. de Vries
Keyword(s):  
Response Time ◽  
Land Subsidence ◽  
Sedimentary Basins ◽  
Sediment Loading ◽  
Dimensional Model ◽  
One Dimensional ◽  
Model Equations ◽  
Sediment Layers ◽  
The Relationship

Abstract. A one-dimensional model is used to investigate the relationship between land subsidence and compaction of basin sediments in response to sediment loading. Analysis of the model equations and numerical experiments demonstrate quasi-linear systems behaviour and show that rates of land subsidence due to compaction: (i) can attain a significant fraction (>40%) of the long-term sedimentation rate; (ii) are hydrodynamically delayed with respect to sediment loading. The delay is controlled by a compaction response time τc that can reach values of 10-5-107 yr for thick shale sequences. Both the behaviour of single sediment layers and multiple-layer systems are analysed. Subsequently the model is applied to the coastal area of the Netherlands to illustrate that lateral variability in compaction-derived land subsidence in sedimentary basins largely reflects the spatial variability in both sediment loading and compaction response time. Typical rates of compaction-derived subsidence predicted by the model are of the order of 0.1 mm/yr but may reach values in excess of 1 mm/yr under favourable conditions.

scholarly journals The hyperpolarization-activated current shifts the dynamic range of a voltage-dependent electrical synapse

2021 ◽  
Author(s):  
Wolfgang Stein ◽  
Margaret DeMaegd ◽  
Lena Yolanda Braun ◽  
Andrés G Vidal-Gadea ◽  
Allison L Harris ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Motor Neuron ◽  
Axon Terminal ◽  
Voltage Dependence ◽  
Dynamic Range ◽  
Complex Dynamics ◽  
Ionic Current ◽  
Electrical Synapse ◽  
Resting Membrane Potential ◽  
Voltage Dependent

Like their chemical counterparts, electrical synapses show complex dynamics such as rectification and voltage dependence that interact with other electrical processes in neurons. The consequences arising from these interactions for the electrical behavior of the synapse, and the dynamics they create, remain largely unexplored. Using a voltage-dependent electrical synapse between a descending modulatory projection neuron (MCN1) and a motor neuron (LG) in the crustacean stomatogastric ganglion, we find that the influence of the hyperpolarization-activated inward current (Ih) is critical to the function of the electrical synapse. When we blocked Ih with CsCl, the voltage dependence of the electrical synapse shifted by 18.7 mV to more hyperpolarized voltages, placing the dynamic range of the electrical synapse outside of the range of voltages used by the LG motor neuron (-60.2 mV to -44.9 mV). With dual electrode current- and voltage-clamp recordings, we demonstrate that this voltage shift is due to a sustained effect of Ih on the presynaptic MCN1 axon terminal membrane potential. Ih-induced depolarization of the axon terminal membrane potential increased the electrical postsynaptic potentials and currents. With Ih present, the axon terminal resting membrane potential depolarized, shifting the dynamic range of the electrical synapse towards the functional range of the motor neuron. We thus demonstrate that the function of an electrical synapse is critically influenced by a voltage-dependent ionic current (Ih).

Factors affectig the response time of an optical-fibre reflectance pH sensor

1995 ◽  
Vol 51 (2-3) ◽  
pp. 129-134 ◽  
Author(s):  
S.H. Alabbas ◽  
D.C. Ashworth ◽  
B. Bezzaa ◽  
S.A. Momin ◽  
R. Narayanaswamy
Keyword(s):  
Response Time ◽  
Optical Fibre ◽  
Ph Sensor
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