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Copyright of Journal of Test & Measurement Technology is the property of Publishing Center of North University of China and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper reports on noise modeling of a piezoelectric charge accelerometer with a signal conditioning circuit. The charge output is converted into voltage and amplified using a JFET operational amplifier that has high input resistance and low noise. The noise sources in the whole system include electrical and mechanical thermal noises of the accelerometer, thermal noises of resistors, and voltage and current noises of the operational amplifier. Noise gain of each source is derived from small signal circuit analysis. It is found that the feedback resistor of the operational amplifier is a major source of noise in low frequencies, whereas electrical thermal noise of the accelerometer dominates the rest of spectrum. This method can be used to pair a highly sensitive sensor with a single JFET operational amplifier instead of a multi-stage signal conditioning circuit. [ABSTRACT FROM AUTHOR]

Copyright of Frontiers of Information Technology & Electronic Engineering is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper reports on noise modeling of a piezoelectric charge accelerometer with a signal conditioning circuit. The charge output is converted into voltage and amplified using a JFET operational amplifier that has high input resistance and low noise. The noise sources in the whole system include electrical and mechanical thermal noises of the accelerometer, thermal noises of resistors, and voltage and current noises of the operational amplifier. Noise gain of each source is derived from small signal circuit analysis. It is found that the feedback resistor of the operational amplifier is a major source of noise in low frequencies, whereas electrical thermal noise of the accelerometer dominates the rest of spectrum. This method can be used to pair a highly sensitive sensor with a single JFET operational amplifier instead of a multi-stage signal conditioning circuit.

This article presents the design of a readout circuit for charge-output sensor arrays integrated on a flexible substrate. The charge-integrating amplifier is built with a current-output transimpedance amplifier that includes the integrator function with reset. The charge-integrating amplifier has a fully differential internal topology, improving over single-ended design, including the feedback amplifier implemented specifically as a Nauta-transconductor. The readout circuit has been manufactured in a 3- $\mu \text{m}$ low-temperature polysilicon process on foil and measured, achieving a bandwidth of 200 kHz, operation at a 5-V supply while consuming 586- $\mu \text{W}$ power and maintaining a maximum integral nonlinearity of 5%.

Since the introduction of adaptive systems for corrective measures, static and dynamic disturbances have been reduced through the manipulation of surface shape in a well-controlled manner. One important application where adaptive systems are highly needed is in the future photo-lithography machines, particularly the wafer table where disturbances affect overlay and focus performance. To reduce overlay and focus errors, a dense array of actuators must be integrated into the wafer table to apply both in- and out-of-plane corrective deformations to the wafer surface. To realize a certain wafer shape, influence functions are linearly superimposed. Accurate models of the influence functions result in an accurate prediction of the final wafer shape. To reduce calibration errors, the influence function of every actuator needs to be determined. Here, we propose a technique to rapidly measure the influence function: the influence function measurement (IFM) technique. Using the actuate-sense property of piezoelectric materials, the influence function is determined by activating one piezo-actuator and measuring the charge induced on the neighboring piezo-actuators. The measured charges are compared to the results of finite element simulations and the absolute difference of 0.3 % is reported for the inter-actuator charge coupling parameters. This clearly indicates the potential of the proposed technique. Note to Practitioners—A critical step during the integrated-circuit lithographic fabrication process is the exposure. A particular practical challenge in this step is to correct for the mismatch between the optical image plane and the wafer surface, caused by wafer deformations. The mismatch negatively impacts the overlay and focus performance. To reduce the mismatch, actuators can be embedded into the wafer table to counteract wafer deformations, where the overall wafer surface shape is a superposition of each actuator’s influence function. As part of the calibration for the embedded actuators, their influence functions are measured and stored. However, errors arise when influence functions are not measured for every actuator. Additionally, for different wafers, the influence functions vary hence the calibration should be done per wafer. This calibration process takes time and should not influence throughput. Our paper presents a viable approach that reduces the calibration time of active wafer tables, which is also relevant for other adaptive systems such as deformable mirrors. Since the technique requires the actuators to be mechanically coupled, it is limited to continuous surfaces. The proposed technique is numerically tested and experimentally verified to demonstrate performance. [ABSTRACT FROM AUTHOR]

This paper describes the design and operation of a programmable charge amplifier for a piezoelectric sensor. An operational amplifier (op-amp) circuit operates the charge amplifier. The purpose of this paper was to design and explain a novel approach for programmable charge amplifiers. A programmable charge amplifier is created by a host digitally (Serial Peripheral Interface (SPI)) and a network of negative feedback, which is a network of resistors and capacitors (RC) connected between an output and inverter input node of an op-amp, where the feedback capacitor is 15 pF and resistors are 12.5, 25, 50, 100, and 200 k. The analog switch was used to connect serial to RC and subsequently to SPI. The suggested circuit was developed and evaluated using discrete components; also, the programmable circuit design and results were generated using Linear Technology's Integrated Circuit Emphasis (LTSPICE) simulation software. It is powered by a ±5V battery. The open loop (AOL), Noise Gain (NG), and phase margin have all been demonstrated in ac analysis. AOL and UGF are set for varied all switches (AOL 107.26 dB and UGF 8.6 MHz), however NG exhibits stability when the feedback capacitor is larger than 15 pF and the feedback resistance is fixed since the design has a Rate-Of-Closure (ROC) smaller than 20 dB. On the other side, the phase margin is also stable. When the switches (the 5-bits of SPI) are activated, the feedback capacitor is set to 15 pF, resulting in the optimum stability, output voltage, settling time, and slew rate. These have been completed in the time domain (transient analysis). [ABSTRACT FROM AUTHOR]

Copyright of Computer Measurement & Control is the property of Magazine Agency of Computer Measurement & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents the updates implemented by the Vibration Laboratory of INMETRO on the electrical calibration of charge conditioning amplifiers. We can now carry out both standard classical calibrations with fixed in-series capacitors and including an adjustable parallel capacitance to match the total capacitance of a given pair of accelerometer plus cable. The calibration system and some analysis of measurement results are presented.

The charge-generating sensors are widely used in many applications in consumer, automotive and medical electronics. They generate a charge proportional to the applied input quantity: pressure, temperature, acceleration, strain, light, etc. Usually, charge amplifiers are used to register such signals. The charge amplifier is an integrator that integrates the input current over time. In continuous-time signal processing, a parallel resistor is used to dissipate the energy stored on the integration capacitor, and such self-zeroed integrator circuits are known as lossy integrators. To achieve low-frequency operation, when a capacitor is in the picofarad range, a very high-ohmic resistor, in the range of gigaohms, must be used. Such a high-ohmic resistor increases the output offset voltage to an unacceptable level. To overcome the output offset problems, a composite charge amplifier has been recently introduced. This paper presents an innovative lossy integrator readout circuit which contains only one opamp in the feedback. The circuit can be easily adapted to the needed gain and cut-off frequency. Its operation is validated by experimental results. The sufficiently low high-pass cut-off frequency allows the circuit to be used for biosignal amplification. Heart and respiration rates can be easily recorded with piezoelectric sensors attached to the wrist or lung wall. The presented circuit can benefit many applications where charge-to-voltage conversion is needed. [ABSTRACT FROM AUTHOR]

Electrocardiogram (ECG) records the electrical activity of the heart and is the most significant diagnostic indicator of health. The electrical activity propagates towards the skin and is typically measured using gel silver/silver chloride (Ag/AgCl) electrodes. The quality of the measured signal depends on the amplitude of the electrical activity, the conductivity of the tissues and skin, and that of the measuring electrode. Gel electrodes can cause skin irritability and are not suitable for long-term measurements requiring the diagnosis of paroxysmal arrhythmias. Dry electrodes are comparatively comfortable to wear but are highly dependent on body hair, sweating, and movement. Non-contact electrodes on the other hand avoid ohmic contact with the skin by providing a capacitive coupling between the skin and the electrode. They can be easily worn over clothing or can be measured from a distance. However, motion artefact remains the biggest challenge in such systems. This study proposes a novel two-channel circuitry for ECG acquisition along with a mathematical model to mitigate the effect of changing sensor-electrode capacitance in non-contact sensors. This method was modeled and validated at different sensor-electrode positions or air-gaps. The effect of change in mutual and parasitic capacitance between the sensor's channels, body tissue impedance, and the ratio of the areas of the two channels was also analysed in terms of Signal to Noise Ratio (SNR). The highest SNRs were achieved with smaller air-gaps and higher ratios of channels' areas. [Display omitted] • Motion artefact remains a major challenge in ambulatory and capacitive Electrocardiogram monitoring. • A novel technology that can be used for long-term and efficiently reject/eliminate motion artefacts has been proposed. • Signal reconstruction was possible using a two-channel electronic circuit and mathematical equations. • This study considered mutual and parasitic capacitances, tissue impedances, and electrode area changes. [ABSTRACT FROM AUTHOR]

In this contribution, we propose a fully printed charge amplifier for on-skin biosignal measurements. The amplifier is fabricated on an ultra-thin parylene substrate and consists of organic transistors, integrated bias and feedback resistors, and a feedback capacitor. The fabrication process utilizes inkjet-printed Ag ink for source, drain, gate, and capacitor electrode metallization as well as for the interconnects between the amplifier elements. Dispensed polystyrene, 2,7-dihexyl-dithieno[2,3-d;2',3'-d']benzo[1,2-b;4,5-b']dithiophene (PS:DTBDT-C6), is used as the transistor channel material, dispensed poly(3-hexylthiophene) (P3HT) as the high-resistivity material for the printed resistors, and parylene as the capacitor dielectric. A pass band optimized for pulse-wave measurement (60 mHz to 36 Hz) is achieved with a maximum charge amplification of 1.6 V/nC. To demonstrate the potential of the proposed printed amplifier, a radial arterial pulsewave signal recorded with a printed piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE) sensor was fed to it and the output was analyzed to quantify the similarity of the pulse-wave features calculated from the original signal and the amplifier output. The amplified signal contains all the essential features of a pulse wave, such as both systolic waves, the dicrotic notch, and diastolic wave, which enable the accurate derivation of the clinically relevant indices utilized in the evaluation of vascular health.

Methods for measuring deposit parameters are often based on a capacitance or conductivity measurement aimed at estimating, e.g. deposit moisture content. In practice, these methods fail for materials with a low degree of homogeneity, a diverse porous structure or high conductivity, e.g. due to a high water content. This article demonstrates an approach that enables a more precise estimation of the parameters of any deposit. The presented method involves the use of a measuring system in a charge amplifier configuration and the application of a technique using lock-in detection or a lock-in voltmeter to determine resistance and capacitance parameters of a deposit based on signals received from the measuring system. This method can be successfully used wherever the test deposit material is highly heterogeneous and contains both dielectric and conductive materials. The article presents an example of a solution to a measuring system using two planar electrodes that can be dimensioned depending on the deposit dimensions. It is followed by a presentation of a method for converting the signal from the measuring system into impedance parameters of the deposit using a lock-in voltmeter. The analysis of the operation of the entire measuring system was modelled in Matlab/Simulink, and the operation results were presented. [ABSTRACT FROM AUTHOR]

We describe a charge detector that utilizes a high-gain, differential solid-state amplifier with active reset and a novel technique to measure the gain using a custom optoelectronic system. Implemented in a 180-nm complementary metal–oxide–semiconductor (CMOS) process, the amplifier realizes a high gain of $8.9~\mu \text{V}/\text{e}-$ and single-pass rms noise of 475e− for 10-ms time interval with a 300-kHz low-pass filter corner. Operating at a sampling frequency of 10 kHz, the active reset extends the dynamic range of the detector. The amplifier is the first instance of a charge detector that combines a differential topology, active reset, and small feedback capacitors for low-noise, high-gain, high-dynamic-range, and robust operations. The proposed optoelectronic test system injects an adjustable input photocurrent as low as 33 pA to precisely quantify the detector’s gain without the need for a known calibration capacitance. The amplifier is directly wire-bonded to a PCB that has a built-in 1-cm2 Faraday cup. The gain and noise performance have been characterized for a range of input capacitance, and the results show good agreement with simulations. The test system additionally demonstrates the ability to inject a time-varying input at the picoamphere levels to characterize the dynamic response of the detector. An electrospray system confirms that the detector responds to free-space charge and that it can process an input as large as 56 000e− without saturation. The compact and high sensitivity design qualify the device for use in charge detection applications, such as mass spectrometry and space instruments. [ABSTRACT FROM AUTHOR]

A low-power ultrasonic communication front end conceived for cargo container monitoring is presented. Two piezoelectric transducers (PTs) operating at 40 kHz are fixed to the metallic wall by means of a customized magnetic case, allowing a noninvasive inside–outside communication preserving the container integrity. Once the resulting ultrasonic channel is characterized, an experimental measurement setup based on field-programmable gate array (FPGA) is implemented for testing some basic modulation and detection schemes in terms of bit error rate (BER), also considering their robustness against undesired mechanical and electromagnetic perturbations. On this basis, a compact digital differential binary phase-shift keying (DBPSK) modulator using a square carrier signal is proposed. Frequency and amplitude tracking algorithms are designed for optimizing the quality and robustness of the data transmission. Finally, a low-power low-rate (up to few kb/s) architectures based on the previous elements are presented. All the proposed contributions are experimentally validated. [ABSTRACT FROM AUTHOR]

The charge amplifier is an important building block in various electronic circuits. In this paper a new charge amplifier for piezoelectric sensors is introduced. The advantages of the new proposed charge amplifier becomes obvious in the quasi-static applications. In some quasi-static applications the traditional charge amplifiers uses an extremely large feedback resistor (in the range of $\text{G}\Omega $) whereas the proposed charge amplifier no longer requires such extremely large resistors. Moreover the proposed circuit reduces the output offset voltage significantly in comparison with conventional charge amplifier. The proposed circuit can be also implemented by using general purpose JFET operational amplifiers instead of using electrometer operational amplifiers therefore the cost of implementation will be reduced significantly in comparison with conventional charge amplifier. The proposed charge amplifier was assembled by using general purpose JFET Op-Amp to capture and amplify the output voltage of the piezoelectric vibration sensor Minisense100. In this experiment the low-cutoff frequency and the gain of the proposed charge amplifier were set equal to 0.2Hz and 20.5 dB respectively. The output offset voltage of the circuit was measured equal to 210 $\mu \text{V}$.The measurement of very small vibration (±0.015g) showed a relative error equal to 2.1% with respect to the value which is obtained by using vibration meter as reference. [ABSTRACT FROM AUTHOR]

A charge amplifier with noise peaking suppression and gain drop compensation is proposed. By utilizing the proposed Quasi-Miller RC network, the noise peaking is suppressed and gain drop is compensated, which alleviates the design trade-off between charge gain and output root-mean-square (RMS) noise, therefore obtains an improved sensitivity. Meanwhile, the Quasi-Miller RC network permits the charge amplifier to support ultra-low frequency operation without using a huge resistor, which is normally required by the charge amplifier. The fabricated charge amplifier demonstrates an input-referred RMS noise charge of 909 aC, a charge gain of 10.2 V/pC and a 3-dB bandwidth from 80 Hz to 38 MHz. Low noise and high charge gain are obtained simultaneously. Meanwhile, extremely low cut-off frequency is also obtained, which is beneficial to maintain the signal integrity. [ABSTRACT FROM AUTHOR]

We present a measurement system capable to detect and reconstruct the trajectory of moving charged debris expelled with the exhaust gases or circulating in the lubricating oil of engines, aero-engines, or gas turbines. The measurement technique is based on a circular array of three electrostatic sensors used to estimate the trajectory, the charge, and the velocity of a moving charged particle. We discuss methods to process the information provided by the sensors, combining physical models and the geometrical characteristics of the sensor array, providing a theoretical characterization of the measurement accuracy, which is shown to be not dependent on the direction of the particle motion with respect to the sensor placement. The information obtained with the measurement system can be used to reject false positives when the sensors and the front-end electronics are used in noisy environments. [ABSTRACT FROM AUTHOR]

The results and methodology of the experiment on the definition of impulse pressure, created by a generator of a plasma-impulse impact in oil, are described. Excessive impulse pressure was measured at a given distance from the axis of the generator in various samples of oil differing in their physical-chemical characteristics. [ABSTRACT FROM AUTHOR]

Copyright of Electronic Components & Materials is the property of Electronic Components & Materials and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a catheter-based capacitive force sensor interface for cardiovascular diagnosis. The force sensor is implemented on a flexible printed circuit board (FPCB) substrate with a force-sensitive polydimethylsiloxane (PDMS), and a force-induced change in a capacitance of the sensor is measured by a precision capacitive sensor interface. To recover the performance degradation caused by the large parasitic capacitance ${\rm C}_{\rm P}$ of a long catheter, we present a parasitic insensitive analog front-end (AFE) with active ${\rm C}_{\rm P}$ cancellation, which employs a charge amplifier and a negative capacitor at the virtual ground of the charge amplifier. The prototype sensor was measured with a force loader in whole blood. The proposed AFE successfully cancels ${\rm C}_{\rm P}$ of 348 pF in a 0.9-m-long sensor and measurement results show the SNR of 53.8 dB and the capacitance resolution of 16 aF, a 19.6 dB improvement by canceling nonideal effect of ${\rm C}_{\rm P}$. This corresponds to a force resolution of 2.22 gf, which is 9.29 $\times$ reduction compared to the work without the ${\rm C}_{\rm P}$ cancellation. The proposed sensor interface is insensitive to ${\rm C}_{\rm P}$ from hundreds to 1-nF level, and the force-dependent stiffness of two different tissues has been successfully distinguished with an ex-vivo experiment. The proposed sensor interface enables the integration of capacitive force sensors in a smart catheter. [ABSTRACT FROM AUTHOR]

With increasing emphasis on implantable and portable medical devices, low-power, small-chip-area sensor readout systems realized in lab-on-a-chip (LOC) platforms are gaining more and more importance. The main building blocks of the LOC system include a front-end transducer that generates an electrical signal in response to the presence of an analyte of interest, signal processing electronics to process the signal to comply with a specific transmission protocol, and a low-power transmitter, all realized in a single integrated circuit platform. Low power consumption and compactness of the components are essential requirements of the LOC system. This brief presents a novel charge sensitive pre-amplifier developed in a standard 180-nm CMOS process suitable for implementing in an LOC platform. The pre-amplifier converts the charge generated by a pyroelectric transducer into a voltage signal, which provides a measurement of the temperature variation in biological fluids. The proposed design is capable of providing 0.8-mV/pC gain while consuming only $2.1~{\mu }\text{W}$ of power. The pre-amplifier composed of integrated components occupies an area of 0.038 mm2. [ABSTRACT FROM AUTHOR]

A comprehensive noise model of a junction gate field-effect transistor (JFET) charge amplifier is presented for applications with piezoelectric sensors. Based on this previously reported amplifier structure, a noise equivalent circuit is derived and discussed. Universal noise gain expressions for each of the twelve considered noise sources are given. By means of an analytical description of the charge amplifier’s noise behavior, the design and optimization of such preamplifiers for various capacitive microelectromechanical sensor systems will be distinctly simplified. Calculations of the noise floor are compared with measurements with a cantilever-type magnetoelectric sensor and with the performance of a so far commonly utilized basic charge amplifier. With the JFET charge amplifier a noise reduction of approximately 22 dB is achieved in the vicinity of the utilized sensor’s resonance frequency of 7.45 kHz. The reported amplifier is the first which has no negative influence on the total noise level of a resonant magnetoelectric sensor system. [ABSTRACT FROM PUBLISHER]

Copyright of Piezoelectrics & Acoustooptics is the property of Piezoelectric & Acoustooptic and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a methodology of monitoring respiration pattern using piezoelectric transducer incorporating CMOS integrated circuits for signal processing and data transmission. As a proof of concept, the system has been tested by placing electrodes on human chest using adhesive hydrogel to detect the pulsatile vibration due to respiration. The system can be used either as a wearable device itself or alternatively can be attached to a jacket or a chest belt. The front-end transducer is a piezoelectric material-based sensor, which is comprised of a ferroelectric polymer named polyvinylidene-fluoride (PVDF). PVDF is also biocompatible, which makes the sensor suitable to be used as a wearable device. The charge produced by the sensor is converted to a proportional voltage signal with the help of a charge amplifier designed in a standard 130-nm CMOS process with eight metal and one poly layer. The analog voltage signal acquired from the charge amplifier is then converted into a digital signal using a reconfigurable pipelined analog-to-digital converter for ease of transmission. An impulse-radio ultra-wideband transmitter operating in the frequency range of 3.1–5 GHz is designed for wireless transmission of the data. The smaller footprint, lighter weight, wireless telemetry, and low-cost material along with the low-power integrated CMOS circuitry for signal processing and data transmission make the proposed system an attractive choice for stable respiration monitoring system. [ABSTRACT FROM PUBLISHER]