scholarly journals Drift rejection differential frontend for single plate capacitive sensors

2020 ◽  
Author(s):  
Mihai T. Lazarescu
Keyword(s):  
Random Noise ◽  
Discharge Voltage ◽  
Differential Capacitance ◽  
Constant Current ◽  
Capacitance Measurement ◽  
Capacitive Sensors ◽  
Measurement Sensitivity ◽  
Charge Migration ◽  
Single Plate

Using capacitive sensors at long ranges (10-20x their plate diameter) for long term environmental sensing can be limited by slow but significant measurement drifts that can often far exceed the small capacitance variations of interest, which can be around 0.01% or less. We propose a differential capacitance measurement method that rejects the quasi-constant drift currents for single plate capacitive sensors by averaging the absolute slope values of adjacent charge-discharge voltage ramps of the plate capacitance, under constant current. Compared analytically and in simulations with period modulation techniques using astable multivibrators, our method shows much better rejection of drifts due to quasi-constant charge migration and improved random noise attenuation, while preserving the measurement sensitivity. We also provide an implementation example that avoids errors caused by some types of ramp distortions and improves noise reduction.<br>

scholarly journals Drift rejection differential frontend for single plate capacitive sensors

2020 ◽  
Author(s):  
Mihai T. Lazarescu
Keyword(s):  
Random Noise ◽  
Discharge Voltage ◽  
Differential Capacitance ◽  
Constant Current ◽  
Capacitance Measurement ◽  
Capacitive Sensors ◽  
Measurement Sensitivity ◽  
Charge Migration ◽  
Single Plate

Using capacitive sensors at long ranges (10-20x their plate diameter) for long term environmental sensing can be limited by slow but significant measurement drifts that can often far exceed the small capacitance variations of interest, which can be around 0.01% or less. We propose a differential capacitance measurement method that rejects the quasi-constant drift currents for single plate capacitive sensors by averaging the absolute slope values of adjacent charge-discharge voltage ramps of the plate capacitance, under constant current. Compared analytically and in simulations with period modulation techniques using astable multivibrators, our method shows much better rejection of drifts due to quasi-constant charge migration and improved random noise attenuation, while preserving the measurement sensitivity. We also provide an implementation example that avoids errors caused by some types of ramp distortions and improves noise reduction.<br>

Research on Small-Capacity Capacitor Type Sensor Detection Method

2014 ◽  
Vol 981 ◽  
pp. 594-597
Author(s):  
Wei Tong Hu ◽  
Yu Xuan Zhang ◽  
Yan Sun ◽  
Wang Sheng Liu ◽  
Li Zhong Zhang
Keyword(s):  
Capacitance Measurement ◽  
Capacitive Sensors ◽  
Measurement Circuit ◽  
Temperature Drift ◽  
Long Term Stability ◽  
Value Range ◽  
Special Circumstances ◽  
Output Capacitance ◽  
Sensor Detection

In the field of industrial measurement, capacitive sensors are widely used. In many types of capacitive sensors, the output capacitance value range of many sensors is very small, generally between 10pF to 1000pF, but accuracy is usually required to be more than one thousandth. The conventional method of detecting capacitance value is generally the capacitor charge and discharge. By charging and discharging time statistics and calculations, capacitance values are deduced finally. The inherent disadvantages of this method are: (1) Temperature drift of the measurement circuit is large. (2) The spatial magnetic field under special circumstances impact on measurement circuit. (3) Long-term stability of the device will deteriorate. In this paper, a "capacitance measurement method with reference and comparison" is summed up through a lot of measurement experiments of humidity capacitance, that method can eliminate three kinds of defects in the capacitor charging and discharging process.

scholarly journals Toward High Throughput Core-CBCM CMOS Capacitive Sensors for Life Science Applications: A Novel Current-Mode for High Dynamic Range Circuitry

Sensors ◽  
2018 ◽  
Vol 18 (10) ◽  
pp. 3370 ◽  
Author(s):  
Saghi Forouhi ◽  
Rasoul Dehghani ◽  
Ebrahim Ghafar-Zadeh
Keyword(s):  
High Performance ◽  
Life Science ◽  
Dynamic Range ◽  
Current Mode ◽  
Capacitive Sensor ◽  
Oxide Semiconductor ◽  
Capacitance Measurement ◽  
Biological Research ◽  
Cmos Process ◽  
Capacitive Sensors

This paper proposes a novel charge-based Complementary Metal Oxide Semiconductor (CMOS) capacitive sensor for life science applications. Charge-based capacitance measurement (CBCM) has significantly attracted the attention of researchers for the design and implementation of high-precision CMOS capacitive biosensors. A conventional core-CBCM capacitive sensor consists of a capacitance-to-voltage converter (CVC), followed by a voltage-to-digital converter. In spite of their high accuracy and low complexity, their input dynamic range (IDR) limits the advantages of core-CBCM capacitive sensors for most biological applications, including cellular monitoring. In this paper, after a brief review of core-CBCM capacitive sensors, we address this challenge by proposing a new current-mode core-CBCM design. In this design, we combine CBCM and current-controlled oscillator (CCO) structures to improve the IDR of the capacitive readout circuit. Using a 0.18 μm CMOS process, we demonstrate and discuss the Cadence simulation results to demonstrate the high performance of the proposed circuitry. Based on these results, the proposed circuit offers an IDR ranging from 873 aF to 70 fF with a resolution of about 10 aF. This CMOS capacitive sensor with such a wide IDR can be employed for monitoring cellular and molecular activities that are suitable for biological research and clinical purposes.

Effect of Water Vapor and SOx in Air on the Cathodes of Solid Oxide Fuel Cells

2007 ◽  
Vol 1041 ◽  
Author(s):  
Seon Hye Kim ◽  
Toshihiro Ohshima ◽  
Yusuke Shiratori ◽  
Kohei Itoh ◽  
Kazunari Sasaki
Keyword(s):  
Water Vapor ◽  
Solid Oxide Fuel Cells ◽  
Degradation Mechanism ◽  
Chemical Species ◽  
Cell Voltage ◽  
Ambient Air ◽  
Open Circuit ◽  
Constant Current ◽  
Constant Current Density

AbstractAmbient air is used as an oxygen source in SOFCs to be commercialized. Various chemical species which can lead to poisoning of SOFC cathodes are included as minor constitutions in air, such as water vapor, SOx, NOx and NaCl etc. However, their effects on the cathode performance have not yet well known, even though they are expected to cause a degradation of the electrode performance and to reduce the long-term durability of SOFCs. Therefore, in this study, we focused on the poisoning caused by water vapor and SOx in the oxygen source to clarify their effects on SOFCs performances and to reveal the degradation mechanism of cathodes. SOFCs with typical electrolyte-supported structure were used in this work, which were composed with ScSZ (10 mol% Sc2O3, 1mol% CeO2, 89 mol% ZrO2) plate with the thickness of 200 µm as electrolyte, NiO-ScSZ (mixture of 56 wt% NiO and 44 wt% ScSZ) porous layer as anode, and two cathode layers of LSM ((La0.8Sr0.2)0.98MnO3) and LSM-ScSZ (mixture of 50 wt% LSM and 50 wt% ScSZ). Power generation characteristics of the cells had been analyzed by measuring cell voltage at a constant current density (200 mA/cm2) and by comparing changes in cell impedance, upon supplying the artificially-contaminated air with water vapor or SOx, to the SOFC cathodes at various operational temperatures. High-resolution FESEM (S-5200, Hitachi) was used to analyze microstructural changes caused by the impurities. Mg Kα radiation from a monochromatized X-ray source was used for XPS measurements (ESCA-3400, KRATOS). AC impedance was measured at various temperatures under the open circuit voltage condition by an impedance analyzer (Solatron 1255B/SI 1287, Solatron), in a frequency range from 0.1 to 105 Hz with an amplitude of 10 mV.

Improve small capacitance measurement sensitivity by opto-electronic isolation method

CPEM 2010 ◽  
2010 ◽  
Author(s):  
Wei Wang ◽  
Lu Huang ◽  
Yan Yang ◽  
Dongxue Dai ◽  
Qian Sun ◽  
...  
Keyword(s):  
Capacitance Measurement ◽  
Isolation Method ◽  
Measurement Sensitivity ◽  
Small Capacitance

Research on the System of Supercapacitor Parameters Measurement Based on High and Constant Current Control

2012 ◽  
Vol 241-244 ◽  
pp. 423-428
Author(s):  
Xing Hua Li ◽  
Yuan Peng Li ◽  
Mao Hu Zou
Keyword(s):  
High Precision ◽  
Test System ◽  
Current Control ◽  
Constant Current ◽  
Capacitance Measurement ◽  
High Precision Measurement ◽  
Super Capacitor ◽  
Compensation Methods ◽  
Constant Current Charging ◽  
Parameters Measurement

High and constant current charging and discharging is necessary to improve the precision of supercapacitor parameters measurment. In this paper, three topics are discussed for high-precision measurment of supercapacitor parameters. Firstly, the analysis of the principle of capacitance measurement was described. Secondly, a model of high and constant current control was presented. The model used in the system of supercapacitor parameters measurement was in order to ensure the constant-current accuracy. Finally, several software compensation methods were used to improve accuracy. And then, the experiment results between our system and the American Arbin Instrument Company’s Super Capacitor Test System were compared. The system designed by us shows good performance of high precision measurement.

Rechargeable nonaqueous lithium/Mo6S8 battery

1984 ◽  
Vol 62 (6) ◽  
pp. 527-531 ◽  
Author(s):  
P. J. Mulhern ◽  
R. R. Haering
Keyword(s):  
Discharge Rate ◽  
Active Material ◽  
Rate Capability ◽  
Constant Current ◽  
Electrochemical Cells ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Cycle Life

Electrochemical cells based on the intercalation of lithium into Mo6S8 were examined by derivative constant current chronopotentiometry, in situ X-ray diffraction, and long-term cycling. About three-quarters of the capacity of such cells oeeurs between 2.0 and 2.1 V with most of the remainder near 2.45 V. Li/Mo6S8 cells have a long cycle life, good discharge rate capability, and an energy density of at least 260 W∙h/kg (1 W∙h = 3.6 kJ) of active material. Such cells can be made by starting with cathodes made from ternary Chevrel phase compounds. AyMo6S8 (A = Cu, Fe, Ni), and electrochemically converting these materials to form LixMo6S8.

Effect of SO2 on the Performance of LSCF Cathode

2014 ◽  
Vol 902 ◽  
pp. 41-44 ◽  
Author(s):  
Run Ru Liu ◽  
De Jun Wang ◽  
Leng Jing
Keyword(s):  
Electrochemical Performance ◽  
Microstructural Change ◽  
Cell Performance ◽  
Sulfur Poisoning ◽  
Constant Current ◽  
Sofc Cathode ◽  
Galvanic Current ◽  
Constant Current Density ◽  
Poisoning Effect

Sulfur poisoning effect on the electrochemical performance and long-term durability of SOFC cathode has been investigated for La0.6Sr0.4Co0.2Fe0.8O3(LSCF) by Galvanic Current Interruption (GCI) technology. Cell performance was measured supplying with SO2-containing air to the cathode under a constant current density of 200 mA cm-2. At 800 °C, LSCF cathode showed low tolerance to the sulfur poisoning. SO2tends to react with strontium in LSCF material resulting in the formation of SrSO4in the cathode. This reaction gave rise to microstructural change in the cathode and caused gradual degradation of cell performance.

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