Capacitance Measurement Method Research Articles

A Study of the Effect of Temperature on the Capacitance Characteristics of a Metal-μhemisphere Resonant Gyroscope.

Metal-μhemispherical resonant gyros (M-μHRGs) are widely used in highly dynamic navigation systems in extreme environments due to their high accuracy and structural stability. However, the effect of temperature variations on the capacitance characteristics of M-μHRGs has not been fully investigated, which is crucial for optimizing the performance of the gyro. This study aims to systematically analyze the effect of temperature on the static and dynamic capacitances of M-μHRGs. In this study, an M-μHRG structure based on a 16-tooth metal oscillator is designed, and conducted simulation experiments using non-contact capacitance measurement method and COMSOL Multiphysics 6.2 finite element simulation software in the temperature range of 233.15 K to 343.15 K. The modeling analysis of the static capacitance takes into account the thermal expansion effect, and the results show that static capacitance remains stable across the measured temperature range, with minimal effect from temperature. The dynamic capacitance exhibits significant nonlinear variations under different temperature conditions, especially in the two end temperature intervals (below 273.15 K and above 313.15 K), where the capacitance values show local extremes and fluctuations. In order to capture this nonlinear behavior, the experimental data were smoothed and fitted using the LOESS method, revealing a complex trend of the capacitance variation with temperature. The results show that the M-μHRG has good capacitance stability in the mid-temperature range, but its dynamic performance is significantly affected at extreme temperatures. This study provides a theoretical reference for the optimal design of M-μHRGs in high- and low-temperature environments.

Dual excitation self-balancing capacitance measurement method based on frequency adjustment

The double-ended excitation self-balancing bridge excitation method is a capacitance measurement method with rather a high measurement accuracy currently. However, the reference impedance of the electric bridge limits the traditional self-balancing excitation measurement method, making it difficult to achieve high accuracy and a wide range of capacitance sensor measurements. In the proposed paper, frequency adjustment method is introduced to enable impedance matching between the measured capacitance and the reference resistance. The measurement range is broadened as well as maintaining the accuracy of the capacitance measurement. The measurement circuit is composed of a reference resistor, a bridge in series with the measured capacitance and an operational amplifier follower circuit. First, we roughly measure the input impedance of the operational amplifier and the capacitive reactance of the capacitance under test using a two-step excitation method. Then, the best excitation frequency is calculated to match the reference resistor according to the capacitive reactance under test, and the input impedance of the operational amplifier is re-estimated with the best frequency. Finally, we complete the accurate measurement of the capacitive reactance under test through the use of dual excitation. The experimental results demonstrate the method’s high accuracy measurement within the range of 1.6 pF–16 nF, with the reference resistance set at 1 MΩ and the excitation frequency adjusted between 10 and 100 kHz. Additionally, dual excitation stability testing verifies relative standard deviations in the range of 0.01%–0.12%. Experiments on filter capsule sensing detection show that the proposed frequency adjustment measurement method can perform highly sensitive capacitive sensing measurements under the influence of parasitic effects.

A Novel Measurement Method for the Self-Discharge of Lithium-Ion Cells Employing an Equivalent Resistance Model

Self-discharge is an important indicator to evaluate the quality of lithium-ion cells. This paper proposes a novel method to quickly measure the self-discharge of lithium-ion cells. A self-discharge equivalent model is developed for analyzing self-discharge measurement requirements. The load capacitance in the model is obtained by using the characteristic curve of open circuit voltage and state of charge. Based on the relationship between the weak current and time of the cell in the charging state, the self-discharge resistance is quickly determined. The corresponding measurement process is introduced. The first experiment preliminarily verifies the plausibility of the load capacitance measurement method proposed in this paper. The second experiment uses this new method to investigate the self-discharge dependence of state-of-charge and further analyzes the influence of load capacitance accuracy on measurement. In order to verify the efficiency and accuracy of the new method, a comparison experiment is conducted by three typical methods and the new method. The results show that this new method is useful; the difference between the results is acceptable while the required measurement time is shortened to less than 6 h.

SMALL DIGITAL VIBROMETER

During scientific studies of the operation of ultrasonic equipment in modern technological processes, it is necessary to measure the amplitude of the mechanical vibration of the working tool, which at high frequencies has significant technical complexity. Knowing the magnitude of the amplitude of ultrasonic vibration makes it possible to precisely dose the amount of energy necessary to obtain a high-quality processing product, as well as for constant repeatability of the results of the equipment. Known foreign vibrometers are purposefully produced for specific conditions of use and are characterized by complexity, bulkiness and high cost, which is an obstacle to wide use. Therefore, the purpose of this work is to develop a low-cost, small-sized vibrometer for measuring the amplitude of ultrasonic emitters. For this, a capacitive measurement method with frequency modulation of the carrier frequency is used, which is characterized by high sensitivity and resistance to external interference. This vibrometer consists of two parts: a vibration sensor with an electronic converter of a high-frequency signal into a constant voltage proportional to the vibration amplitude, and a power supply unit and digital signal processing and indication of the amplitude in μm. The vibrometer sensor is mounted on a hinged tripod for ease of installation in any plane at a distance of ≈1 mm from the tested surface. The vibrometer is powered by a 220V network. The vibrometer is equipped with microprocessor processing and indication of the results of measurement of the vibration amplitude, as well as control and indication of the gap between the vibration sensor and the tested surface and stabilization of the amplitude readings when this gap varies within 0.7...1.2 mm. The vibration amplitude measurement range is 0...99 μm, with a resolution of 1 μm. The vibration frequency range is 5...50 kHz. The analog signal from the output of the vibrosensor can be used in the ultrasound generator feeding the piezoelectric transducer as a feedback signal to stabilize the amplitude of the mechanical vibrations of the emitter at the required level.

Capacitance measurement via mechanical self-excited vibration of a cantilever in the electrostatic field

This paper presents a capacitance measurement method based on the self-excited vibration of a cantilever in a steady electrostatic field. The capacitance Cb to be measured is connected to the fixed end of the cantilever and its magnitude is reflected by the pulse voltage difference across the sampling resistance. The test results indicate that capacitance Cb is in a good linear relationship with the pulse voltage difference. When the applied DC voltage is 2.5 kV, the output voltage signal can reach 482.9 V and the measured capacitance to voltage ratio is 14.2 fF/V. The test results also show that the proposed method is insensitive to the geometrical and material parameters of the vibratory cantilever. The lower limit of the capacitance measurement is determined by the parasitic capacitance Cb, para, and its characteristic provides a new approach to measuring the parasitic capacitance of isolated conductors at fF level.

Online capacitive detection method for moisture content of aggregate based on edge effect

The moisture content of aggregate has an important influence on the final mix proportion of concrete and the quality of finished products. The detection methods of moisture content include offline and online. At present, the offline oven-dried method which is inefficient is often used for measurement. The capacitance method is easy to implement, low cost, high precision, low power consumption and fast response. However, the traditional capacitance measurement method must ensure that the space inside the plate is full of medium, which is more suitable for offline measurement. In order to realize online measurement, a moisture content detection method of aggregate based on edge effect is proposed. The wear of the plate can be avoided effectively by using the coplanar scattering field capacitive plate combined with the striker plate. The signal processing circuit uses a single chip solution PCAP01 to effectively improve the anti-interference ability of the detection circuit. The developed sensor is suitable for inner water detection of aggregate. The experimental results show that the effective measurement range of the sensor is 0 ∼ 1.0%,the penetration depth is 10 mm, the resolution is 0.1%, the hysteresis error is 2.69%, and the repeatability error is 10.31%.

Drift Rejection Differential Frontend for Single Plate Capacitive Sensors

Capacitive sensing at long ranges (10x the plate diameter) for long-term environmental monitoring can be limited by slow but significant measurement drifts from charge induction, which can exceed the small capacitance variations of interest, below 0.01%. This paper proposes a slope modulation differential capacitance measurement method for single-plate capacitive sensors operating in loading mode that effectively rejects noise from quasi-constant drift currents. It is based on periodical plate capacitance charge-discharge, like the period modulation frontends (astable multivibrators) that were used in past work, but it uses a constant oscillation period and compares the slopes of adjacent plate voltage ramps. Plate capacitance is calculated by averaging the slope magnitudes, which rejects the noise from quasi-constant drift currents. The sensitivity and noise rejection are compared with the period modulation techniques analytically, and the results are validated using simulations and experiments. They show that human body sensing range doubles and the noise floor is substantially lower compared to the state-of-the-art (period modulation).

Numerical Evaluation of Complex Capacitance Measurement Using Pulse Excitation in Electrical Capacitance Tomography

Electrical capacitance tomography (ECT) is a technique of imaging the distribution of permittivity inside an object under test. Capacitance is measured between the electrodes surrounding the object, and the image is reconstructed from these data by solving the inverse problem. Although both sinusoidal excitation and pulse excitation are used in the sensing circuit, only the AC method is used to measure both components of complex capacitance. In this article, a novel method of complex capacitance measurement using pulse excitation is proposed for ECT. The real and imaginary components are calculated from digital samples of the integrator response. A pulse shape in the front-end circuit was analyzed using the Laplace transform. The numerical simulations of the electric field inside the imaging volume as well as simulations of a pulse excitation in the front-end circuit were performed. The calculation of real and imaginary components using digital samples of the output signal was verified. The permittivity and conductivity images reconstructed for the test object were presented. The method enables imaging of permittivity and conductivity spatial distributions using capacitively coupled electrodes and may be an alternative measurement method for ECT as well as for electrical impedance tomography.

High precision, low excitation capacitance measurement methods from 10 mK to room temperature.

Capacitance measurement is a useful technique in studying quantum devices, as it directly probes the local particle charging properties, i.e., the system compressibility. Here, we report one approach that can measure capacitance from mK to room temperature with excellent accuracy. Our experiments show that such a high-precision technique is able to reveal delicate and essential properties of high-mobility two-dimensional electron systems.

A high voltage capacitance measurement method based on alternating coupled signal injection.

As high voltage pulse power capacitors, ceramic capacitors are widely used in high voltage pulse generators, trigger circuits, laser generators, and other fields. The capacitance of ceramic capacitors is closely related to the direct current (DC) bias voltage. However, the current capacitance measurement methods can only achieve a DC bias of 1 kV, which cannot meet the measurement requirements in high voltage environments. This paper proposes a capacitance measurement method that can accurately measure the capacitance under a DC bias of 3 kV. This method decouples the high DC bias voltage and high frequency alternating small signals and realizes low voltage calibration and high voltage isolation. The experimental results show that the proposed method measures the capacitance under a DC bias of 3 kV with a relative error within ±1%, which makes it possible to accurately quantify the capacitance hysteresis deviation in the process of increasing and decreasing back the voltage.

Contactless transport method of two-dimensional electron system studies

We introduce two contactless measurement methods at extremely low temperature: capacitances and surface acoustic waves. Both methods can be used to study the physical properties of the quantum system through the interaction between electrons and high frequency electric field. We first present preliminary results of high-mobility two-dimensional electron systems studied by a high-precision capacitance measurement method at extremely low temperature. Our setup can resolve < 0.05% variation of a < 1 pF capacitance at 10 mK–300 K and 0–14 T. Second, we also study two-dimensional electron systems using surface acoustic waves. We can use 0.1 nW excitation and obtain < 10<sup>–5</sup> sensitivity. These measurement methods may be widely applied to the study of two-dimensional systems, especially the materials without high quality contacts.

Precision measurement of pixel sensor capacitance

The capacitance of the charge collection node of a sensor system is an important parameter for the design of the analog front-end electronics. The analog front-end of high-granularity sensors like for example hybrid pixel detectors need to be optimized for timing resolution, power consumption, and electronics noise—parameters which all depend on the pixel capacitance. Current pixel detector developments for the HL-LHC upgrade typically use silicon sensors with a pixel size in the order of 50 × 50 μm2 which have a pixel capacitance of several tens of fF, depending on the sensor geometry. We have developed a dedicated integrated circuit to be bump-bonded to a pixel sensor, which enables a precise pixel capacitance measurement by using the charge-based capacitance measurement method. In this paper, we will describe the measurement method and the implementation of the capacitance measurement chip (Pixcap65) and show measurement results of a planar pixel sensor whose pixel capacitance is influenced by variations of the implant geometry.

Temperature dependence of interface state density distribution determined from conductance–frequency measurements in Ni/n-GaP/Al diode

The conductance measurements of the non-annealed (D1) and 400 °C annealed (D2) Ni/n-GaP/Al diodes were made over a wide frequency range of (10 kHz to 5 MHz) and temperature of (100–320 K with steps of 20 K) with bias voltage as a parameter. The capacitance and conductance measurement method is one of the most popular non-destructive methods to obtain information about metal–semiconductor (MS) diode interfaces. The interface state density distribution curves were determined over the band-gap energy near the semiconductor energy midgap. The interface state density (Dit) has been seen to be of the order of ∼1012 eV−1 cm−2. The Dit∼T curves have been plotted for different values of bias voltage. The value of Dit increased with increasing measurement temperature, and with increasing voltage from negative bias to positive bias voltage for both diodes. It was seen that the Dit value for D2 diode was greater than that for the D1 diode at each measurement temperature and bias voltage. It was seen in the interface state energy distribution or density distribution curves that the value of Dit has increased from the valence band maximum (Ev) towards conduction band minimum (Ec) at each measurement temperature.

Measurement of Soil Capacitance Using Pulse Width Technique

Soil water content is an important parameter in many engineering, agricultural and environmental applications. Capacitance measurement methods are used to measure the soil moisture or water content. Many capacitance soil moisture sensors employ a probe consisting of two electrodes. The capacitance between the probes varies as a function of water content in the soil. The capacitance measurement setup has been developed indigenously to measure capacitance of solid samples at low frequencies using integrated circuit of Monostable Multivibrator. The change in pulse width measured by using Tektronix TDS 2024 four channel digital storage oscilloscope. In this paper capacitance of soil samples from different locations of Pune district of Maharashtra State was measured at room temperature. The details of its interface to measure capacitance of soil samples and evaluated results are explained in this paper.

Online measurement of distributed capacitance in distribution network

The distributed capacitance current of distribution network is the main factor of single-phase grounding current. In the current engineering, the distributed capacitance current is mostly measured by testing the distributed capacitance. Using the volt and ampere relationship of capacitor element can be indirectly realizing the test of distributed capacitance current. Most of the existing distributed capacitance measurement methods use the total impedance of the system to replace the distributed capacitance, which is easily to cause measurement error. Based on the analysis of the distribution network operation, this paper proposes an online measurement technology of distribution network which can precisely test the distributed capacitance. The physical engineering model is established, and the simulation research and design is carried out. The research shows that the online test technology of distributed capacitance can control the test accuracy below 1%, which can effectively make up for the deficiency of the existing distributed capacitance testing technology. It can realize the online detection of the distributed capacitance current of the distribution network, and ensure the operation safety.

Abnormal Hump Effect Induced by Hydrogen Diffusion During Self-Heating Stress in Top-Gate Amorphous InGaZnO TFTs

The mechanism of hydrogen-diffusion-induced electrical degradation under the self-heating effect for a top-gate amorphous InGaZnO (a-IGZO) thin-film transistor is examined in this article. Joule heating occurs in channels under high operating currents. The hydrogen in the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{n}^{+}$ </tex-math></inline-formula> a-IGZO source/drain then diffuses into the channel and shifts the threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{{\text {TH}}}$ </tex-math></inline-formula> ) in the negative direction. As the thermal conductivity of a-IGZO is lower than that of the surrounding insulator, the heat is preferentially dissipated from the sides of the channel. However, the heat in the center of the channel cannot by dissipated quickly. In addition, the unequal channel thermal effect induces a hump effect in the electrical characteristics, which is observed in COMSOL simulations. Hydrogen diffusion under self-heating stress (SHS) operation increases both the effective channel length and parasitic capacitance. The capacitance measurement method is used to clarify the mechanisms of these abnormal phenomena. Finally, the Joule heating effect is eliminated in a low-temperature environment at 200 K with a constant current, confirming that the degradation is indeed caused by the Joule heating effect.

A comparative study of supercapacitor capacitance characterization methods.

This paper compares two supercapacitor capacitance measurement methods: the method 1A of the IEC standard 62391-1 and a method utilizing the total charge stored in the supercapacitor. These two methods are applied to three supercapacitor samples with different rated capacitances from different manufacturers at various terminal voltages. Experimental results show that the capacitance determined using the IEC method decreases when the discharge current increases. Besides, the capacitance measured using the IEC method is lower than that estimated using the total charge method. Moreover, the ratio of the capacitance estimated using the total charge method to the one measured using the IEC method is greater when the supercapacitor terminal voltage is lower. These three observations on the capacitances measured using the two methods are explained by analyzing a five-branch RC ladder circuit model capturing multiple aspects of the supercapacitor physics: porous electrode structure, voltage dependence of capacitance, charge redistribution, and self-discharge.

Magnetic Augmented Self-sensing Flexible Electroadhesive Grippers

Current electroadhesion (EA) grippers cannot be used to lift objects with limited contact areas. Current electromagnetic adhesion (MA) grippers cannot be used to grip nonferrous materials. Here, we combine EA and MA into a monolithic, electrically controllable, flexible, and hybrid electro/magneto-adhesive (E/MA), to offer EA grippers augmented with magnetoadhesion and MA grippers augmented with electroadhesion. This E/MA was achieved by exploiting two intertwined coplanar coils inspired by Tesla's flat bifilar coil. By appropriate electrical connections an electromagnetic field is generated – driving magnetic attraction—or an electric field is generated—delivering electroadhesion—or both fields can be generated simultaneously. As a result, the E/MA grippers cannot only be used to lift ferrous and nonferrous materials, but also low-density objects, such as office paper clips. We also present a customized capacitance measurement method to enable an autonomous material handling system without embedding external sensors. E/MA grippers have the potential to expand the capabilities and impact of soft robotics and industrial gripper systems.

Development of the Particulate Matter Sensor for Diesel Engine

This paper proposes a development of the low-cost and capacitance measurement particulate matter (PM) sensor to monitor diesel particulate filter (DPF) failure. Compared to the resistance measurement PM sensor that is affected by ash accumulated between electrodes due to periodic PM regeneration, capacitance measurement method has the advantage of compensating with capacitance measurement even though the initial ash is present. To reduce the manufacturing cost, we fabricated the proposed sensor with alumina instead of zirconia as the substrate and reduced the sensing area by 26 % compared to the conventional PM sensor. As a result of evaluation, the response time of 5 min required to reach a threshold 50pF at the exhaust gas flow rate of 70 kg/h and PM concentration of 10 mg/m3. It is similar to the conventional PM sensor which takes 343 sec. Durability of the alumina-based PM sensor investigated through thermal endurance test, and the sensor features (C0, R0heater and response time) indicated no significant difference before and after the test.

Development of Capacitance Tools: At-Line Method for Assessing Biomass of Mammalian Cell Culture and Fixed Cell Calibration Standard.

Capacitance is used to monitor "biomass" in cell culture and fermentation processes. The present work explores various ways to support good manufacturing practices (GMP) use and create robust methods that can assure proper performance of capacitance equipment. An at-line capacitance measurement method is particularly valuable as it can be used to correct or confirm online measurements from bioreactors. To obtain consistent predictions of online capacitance, the at-line method requires appropriate control of culture temperature, vessel geometry, mixing, and timing. The at-line method yields values that differ systematically from online values, but the variation is ≤11% for two cell lines tested. A cell line-specific conversion factor addresses the difference and enables accurate predictions of online capacitance values. In addition to the at-line method, verification of equipment performance is further enabled by using formaldehyde-treated cell standards. The cell-derived standards create a stabilized system for studying capacitance and recapitulate the performance of metabolically active cell culture. The formaldehyde-treated cells, however, require a much greater conversion factor to predict online outputs. The stabilized system proves useful for evaluation and calibration of capacitance measuring systems. The at-line method and stabilized cell-derived suspensions support use of capacitance for process control in large scale mammalian cell culture.