Weak Current Signal Research Articles

Circuit design of a novel front readout circuit for SiC neutron detector with leakage current compensation

Radiation detectors have broad application prospects in environmental radiation monitoring, radiation source identification, biomedical imaging, space exploration, astrophysics, other radiation detection and imaging fields. Among the third generation semiconductors, the properties of 4H-SiC are more suitable for making high-temperature and strong radiation neutron detectors. SiC materials have become a current research hotspot. In this paper a special readout integrated circuit is designed for the extremely weak current pulse signal output by SiC trench neutron detector. A leakage current compensation circuit is designed for the influence of leakage current on charge sensitive amplifier(CSA) output baseline. The noise of CSA output is analyzed and the noise minimization is carried out. The circuit can quickly respond to the input signal and extract the energy and time information. The circuit is designed based on the DB Hitek 0.18μm CMOS process model. The layout design is achieved and the post-simulation is completed. Simulated results show that the equivalent input charge range of the system is about 2fC ∼ 20fC. The charge conversion gain is 88mV/fC. The nonlinear error is within 1.6 %. Moreover, the equivalent noise charge is 22e-. The circuit has the advantages of high gain, high linearity and low noise. Therefore, the circuit can effectively adapt to the characteristics of the charge signal output from SiC trench neutron detectors and amplify the output charge signal.

Simple and sensitive voltammetric sensor for in‐situ clinical and environmental 17‐β‐estradiol monitoring

AbstractThe direct electrochemical oxidation of 17‐β‐estradiol (E2) at conventional electrodes gives weak current signals making detection at trace levels difficult, as required for clinical and environmental applications. In order to strengthen the electrochemical behavior of E2, a simple and sensitive sensor has been realized based on a graphite screen printed electrode (GSPE) functionalized according to a two‐step procedure: i) drop‐casting deposition of gold nanoparticles (AuNPs); ii) electropolymerization of methylene blue (MB). The final PMB‐AuNPs‐GSPE platform was characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The pH value was optimized in order to obtain the best detection efficiency and the highest peak current response was obtained at pH 7.0. The synergistic contributions of both AuNPs and PMB allowed the proposed sensor to show a wide linear range from 0.5 to 125.0 μmol L−1 with a LOD of 41 nmol L−1, long‐term stability and good reproducibility (RSD=2.9 % for n=10). Moreover, the sensor was able to distinguish E2 from several interfering compounds commonly present in urine and river water as well as from other endocrine‐ disrupting chemicals (EDCs), denoting its high specificity to E2 molecule. Finally, the developed electrode platform was successfully applied to the determination of E2 in both human urine and river water samples without any purification step under the standard addition method.

Front-End Circuit for Photomultiplier Tube Signal Readout Based on Recognition of Traffic Signal Images

Photoelectric sensing technology plays a crucial role in vehicular equipment, which is equipped with various photoelectric devices to perceive the surrounding environment and avoid traffic lights and vehicles. This research selects the Hamamatsu H9500, a 256-channel, position-sensitive photomultiplier tube, as the test unit. It aims to simplify signal readout while improving the spatial resolution of the photodetector. This research focuses on designing a charge distribution circuit named Discretized Positioning Circuit (DPC) for the photomultiplier tube, with an additional charge-sensitive front-end amplification and shaping circuit. This circuit can convert the weak current signals from the H9500 into voltage signals. The shaping part of the circuit employs an active CR-RC circuit with weak signal amplification capabilities. This circuit is deployed within the photomultiplier tube, strategically positioned on vehicles to recognize various traffic sign images. The front-end shaping circuit is tested in the experiments, which converts square wave voltage into pulse current using a capacitor. It is observed that the current signal has a certain width and the voltage waveform of the CR differential circuit can be obtained by increasing the input impedance to 1 MΩ. During input voltage amplitude testing, the corrected output signal voltage shows a good linear relationship with the input square wave voltage. This designed front-end shaping circuit is used for signal readout in photomultiplier tubes and deployed in vehicular equipment to collect image information of traffic signs. After image processing, satisfactory recognition results are achieved.

Enhancing blind-dumb assistance through a self-powered tactile sensor-based Braille typing system

Wearable human-machine interfaces (HMI) have made remarkable advancements in communication, education, and healthcare, primarily driven by the rapid growth of the Internet of Things (IoT) and 5G technology. Among the various applications of wearable HMIs, there is a critical need for technologies that aid communication for blind individuals, enabling them to access information independently. However, progress in investigating blind communication has been impeded by challenges related to signal capture limitations and power supply issues. To address these challenges, this paper proposes a groundbreaking smart finger Braille typing system based on the emerging triboelectric nanogenerator (TENG). The objective of this system is to assist the blind in typing without external aid. To build an effective tactile sensing system, two essential components are required: a high-sensitivity tactile sensor and a weak current signal processing circuit. In this study, we employed electrostatic spinning to produce degradable friction nanofiber films, which significantly enhanced the sensitivity of the sensor and improved the overall device conversion efficiency. One notable advantage of utilizing TENG as a sensor is that it eliminates the need for an external power supply, ensuring self-sufficiency in the system's operation. Furthermore, we developed a specialized weak current signal processing circuit based on the unique properties of TENG, such as its high impedance and weak current characteristics. The Braille code's six dots will be represented by six self-power tactile (SPT) sensors strategically placed on both hands. By employing various tapping combinations, users can create words, which are then transmitted to mobile devices using Bluetooth technology. By introducing this innovative Braille typing system, we aim to contribute to the global mission of improving information accessibility for blind and partially sighted individuals. This system has the potential to significantly enhance their Braille literacy abilities, bridging the gap between them and the online world.

Integrated biosensing system of electrochemistry and electrophysiology for cortisol and skin conductance analysis on smartphone

High level of mental stress will lead to negative psychological and health consequences, such as insomnia, depression, and cardiovascular disease, which will increase the suicide rate and affect social stability. Mental stress has been proved to be related to biomarkers cortisol and skin conductance, and reflects the complementary advantages of stress monitoring. Based on electrochemistry and electrophysiology analysis technology, combined with microelectronic design and biosensors, this paper constructed an integrated physiological and biochemical sensing system, and an intelligent user interaction system. Firstly, a molecularly imprinted biosensor with gold nanoparticles (AuNPs), prussian blue (PB), and polypyrrole (PPy), achieved highly sensitive detection of cortisol in the range of 1–10000 ng/mL and demonstrating good specificity. The cortisol detection unit used differential pulse voltammetry (DPV) method by dual power amplifier chip AD8674, which was a precision operational amplifier with low noise, low input bias current, and unit gain stability. Then, the skin conductance detection unit was mainly composed of a pulse width modulation (PWM) drive circuit, which was designed to achieve a 100 Hz voltage output. The integrated system was designed with microcontroller module, transimpedance amplifier (TIA) module, power management module, signal transmission module, cortisol and skin conductance detection module, which was suitable for constructing precision voltage control and weak current signal conditioning. Finally, based on the software and hardware platform of smartphones, an intelligent analysis system was developed to improve the portability and user interaction convenience. Our system achieved the physiological and biochemical joint detection for the first time, showing enormous application potential in future multimode sensing monitoring.

SiC/Graphene Film by Laser CVD as an Implantable Sensor Material for Dopamine Detection.

Implantable electrochemical sensor holds great promise in the real-time monitoring of dopamine (DA) to regulate body function. However, the real application of these sensors is limited by the weak current signal of DA in the human body and the poor compatibility of the on-chip microelectronic devices. In this work, a SiC/graphene composite film was fabricated using laser chemical vapor deposition (LCVD) and employed as a DA sensor. The graphene in the porous nanoforest-like SiC framework offered efficient channels for electronic transmission, leading to an enhanced electron transfer rate and consequently an increased current response for DA detection. The three-dimensional (3D) porous network also facilitated the exposure of more catalytic active sites toward DA oxidation. Besides, the wide distribution of graphene in the nanoforest-like SiC films reduced the interfacial resistance of the charge transfer. The SiC/graphene composite film exhibited excellent electrocatalytic activity toward DA oxidation with a low detection limit of 0.11 μM and a high sensitivity of 0.86 μA·μM-1·cm-2. The film electrode also showed a wide linear response for DA in 0.5-78 μM, along with good selectivity, repeatability, and reproducibility. Furthermore, the cell counting kit-8 (CCK-8) and live-dead assays revealed that the film is also biocompatible for biomedical applications. Therefore, the nanoforest-like SiC/graphene composite film via the CVD process enables a promising candidate for an integrated miniature DA biosensor with high detection performance.

Accurate Low Current Measurement Electronics With Self-Calibration Function for Ionization Chamber of Slow Extraction in HIAF

The new wide-range readout electronics with a self-calibration function are designed for ionization chambers (ICs) in the slow extraction of high-intensity heavy-ion accelerator facility (HIAF), booster ring (BRing). These electronics consist of a programmable trans-impedance amplifier (TIA), a self-calibration circuit, an 18-bit analog-to-digital converter (ADC), and a ZYNQ-7015 field-programmable gate array (FPGA). It is capable of monitoring weak current signals of 40 pA–4 mA with a sampling rate of 5 MHz. The ZYNQ-7015 FPGA manages the operation mode of the analog front-end (AFE) and the gain of the TIA. It also performs digital signal processing algorithms and data communication with the host computer. The self-calibration circuit uses a combination of a Schmitt trigger and voltage-to-current (V–I) converters to generate two square wave current signals with different peaks ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2 \mu \text{A}$ </tex-math></inline-formula> and 2 mA). During offline tests, the effective number of bits (ENOB) is 12.98 bits, and the nonlinearity is less than 0.075% for a full scale. Finally, the readout electronics are deployed for ICs’ slow extraction measurements at the extraction line of the cooling storage ring of the heavy-ion research facility in Lanzhou (HIRFL). With the help of a commercial dc-transformer in the cooling storage ring project of heavy ion research facility in Lanzhou (HIRFL-CSR), these electronics not only execute an accurate current measurement, but also can monitor the extraction efficiency reliably. In a word, these electronics play an important role in the fields of extremely weak and high dynamic current signal measurements.

An artificial bridge circuit approach between two biological neurons using nanoscale topologies towards paralytic disorders

The advent of Nanoscale IC technology towards pulse-based neural systems reactivates the dead nervous about restoring the functionality of paralytic disorders. This work reports in first time a design of a novel CMOS biological neuron system, which replaces a dead neuron between two neurons to restore communication in paralyzed individuals. The work binds into three stages: design of a spiking leaky Integrator and Fire (LIF) neuron with refractory period mechanisms, which achieves a low power consumption of 2.4 μW, in the first stage; an adaptive homeostatic synapse with short and long-term spike plasticity, that reconfigure the spiking neuron networks of multichannel sensor electrodes to record the electric signal from the active cell as second stage; the final stage presents a low-power common source current reuse regulated cascode (CS-CR-RGC) TIA for amplifying the weak synapse current signal, which achieves a high gain of 135.71 dBΩ with an optimized noise performance of 0.19 pA/Hz. The entire work is designed and implemented using a CMOS 65 nm commercial process that occupies a die area of 400 μm × 120 μm.

Development of Electromagnetic Current Meter for Marine Environment

Ocean current is one of the most important parameters in ocean observation, and ocean current measurement based on electromagnetic induction is becoming more and more important because of its advantages such as simple structure and high measurement accuracy. However, it is difficult to detect weak current signals in a complex marine environment. In this paper, an electromagnetic induction current measurement scheme based on lock-in amplification technology is proposed. Key technologies such as the evaluation of induced current intensity, overall design, circuit design, and orientation design of the current meter were studied. The prototype of the electromagnetic current meter was developed and tested in the laboratory and at sea. The repeatability of current velocity and current direction was higher than 1.5 cm/s and 1.5°, respectively. A comparison test between the electromagnetic current meter prototype and Nortek ADCP (Acoustic Doppler Current Profiler) installed on a buoy at sea was carried out, and the correlation coefficients of the current velocity and current direction datum were 0.90 and 0.96, respectively. Through continuous on-site and fault-free operations at sea, the experimental data show that the electromagnetic current meter has good adaptability at sea, which provides feasible technical and equipment support for ocean current observation.

A method for identifying weak current signals in distribution equipment based on vector control

A method for identifying weak current signals in distribution equipment based on vector control

A method for identifying weak current signals in distribution equipment based on vector control

A method for identifying weak current signals in distribution equipment based on vector control

Design of a Sampling System for Wide Range nano-current Signal

Space particle radiation will greatly shorten the service life of basic components, resulting in premature failure of aircraft. For newly developed electronic components for space applications, strict anti irradiation performance evaluation must be carried out to master their working characteristics and performance degradation mechanism in space irradiation environment, so as to provide a reliable guarantee for the safe operation of aerospace electronic equipment in orbit. Taking high-voltage power devices such as SiC MOSFET and IGBT as the research object, this paper designs a high-precision weak current signal acquisition and measurement system to continuously monitor its working current under specific track applications, so as to verify the mechanism of space radiation effect and the effectiveness of reinforcement technology. The experimental results show that the system has the advantages of wide range, low noise, high precision and good stability. It can be applied to the experimental verification of high-voltage power devices in various space environments, including space station orbit.

A novel approach for weak current signal processing of self-powered sensor based on TENG

Triboelectric nanogenerator (TENG) is a new high-efficiency electromechanical conversion mode proposed in recent years. When triboelectric nanogenerator is used as sensor, like other types of sensors, it can use current signal as sensing signal, but it outputs weak current signal with high impedance, which is not conducive to direct application. In this paper, a preprocessing method for weak current signal is proposed. The I/V conversion measurement method and the direct measurement method are theoretically analyzed, and the principle of parameter selection of circuit components is provided respectively. After that, the experiment of Contact Separated Triboelectric Nanogenerator (CS-TENG) is used to verify that the proposed I/V conversion measurement method has higher accuracy than the direct measurement method, and then the Rotary Triboelectric Nanogenerator (R-TENG) and the single electrode triboelectric nanogenerator (S-TENG) are used further verifies the design theory of the I/V conversion measurement method. Finally, it is concluded that the I/V conversion measurement method can convert the high impedance weak current signal output by TENG into a low impedance low voltage signal. Through reasonable component parameter selection, the measurement error can be controlled within 6 %, which can not only be used in current signal extraction of TENG, but also be expected to be used for current signal characterization in TENG when TENG is used as an energy harvester.

A novel and label-free electrochemical aptasensor based on exonuclease III and G-quadruplex DNAzyme for sensitive and selective detection of metronidazole

A novel and label-free electrochemical aptasensor based on exonuclease III (Exo III) and G-quadruplex DNAzyme has been first designed to detect metronidazole (MNZ) sensitively and selectively in this paper. Capture probe (CP), helper probe (HP) and aptamer (Apt) hybridize to form double-stranded DNA (dsDNA) structure with a blunt 3′-terminus, resulting in the guanine (G)-rich CP being enclosed in the dsDNA, followed by specific digestion of the 3′-terminus by Exo III to expose the G-rich sequence. At this time, CP can bind with the added hemin to form G-quadruplex DNAzyme which catalyzes the redox reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) and H2O2, generating a strong current signal. However, in the presence of MNZ, the binding of MNZ and aptamer breaks the original blunt 3′-terminus of the dsDNA structure, blocking the subsequent series of reactions, and only a weak current signal can be observed. Under the optimal conditions, the aptasensor showed excellent sensitivity and specificity for the detection of MNZ with a wide linear range from 10 pM to 500 nM and a detection limit as low as 3.0 pM (S/N = 3). The aptasensor constructed based on MNZ aptamer can effectively avoid the interference of other nitro compounds and antibiotics to a certain extent. Compared with other specific recognition elements, the aptasensor possesses the advantages of strong specificity, simple preparation and low cost. Moreover, the proposed aptasensor has been successfully applied to the detection of MNZ in tap water and honey samples.

Sensitive detection of electrophysiology and dopamine vesicular exocytosis of hESC-derived dopaminergic neurons using multifunctional microelectrode array

Clinical transplantation of human embryonic stem cells derived dopaminergic neurons (hESC-DDNs) is expected to be a potential therapy for treating neurodegenerative diseases. However, the assessment of the physiological functions, including electrophysiology and dopamine (DA) vesicular exocytosis of hESC-DDNs are not impeccable currently, which deeply limits the clinical application of hESC-DDNs. To overcome this challenge, we developed a multifunctional microelectrode array (MEA) which can detect both electrophysiological signals and DA vesicular exocytosis. The reduced oxidation graphene, poly(3,4-ethylenedioxythiophene) and poly (sodium-4-styrenesultanate) nanocomposites (rGO/PEDOT:PSS) were electrochemically deposited on the MEAs to improve their electrical characterizations with low impedance and small phase delay, and electrochemical characterizations with low oxidation potential, low detection limit, high sensitivity, wide linear range and high sensitivity. In the hESC-DDNs experiment, the modified MEA could detect electrophysiological signals with low noise (25 μV) and high signal-to-noise ratio (>5.4), and the weak current signals generated by DA vesicular exocytosis with high sensitivity (∼pA), high time resolution (sub-millisecond) and low noise (3 pA). Moreover, due to increased accuracy, the MEA could clearly distinguish two typical kinds of exocytosis spike events (“Spikes with foot” and “Spikes without foot”) and found that the slow and low release through the fusion pore was an important mode of DA vesicular exocytosis in hESC-DDNs. Our work proved that the hESC-DDNs had the basic physiological functions as human dopaminergic neurons, which would be beneficial to the clinical application of the hESC-DDNs.

Short-time and weak signal demodulation for fiber optic current sensors based on backpropagation neural network

It has been challenging to demodulate short-time and weak current signals collected by fiber optic current sensors (FOCSs) under ultra-high voltage, since the background noise can significantly affect the spectra of the current signals. To address this issue, here we propose a novel FOCS demodulation method based on backpropagation neural network, where the impact of the noise on the measurement can be largely reduced. The demodulation method can determine the amplitudes of short time series of weak currents with high resolution and accuracy. To evaluate the performance of the proposed method, the demodulation accuracy and robustness of the method are experimentally investigated and compared with those of the traditional fast Fourier transform (FFT) method. The experimental results show that our method can produce reliable results when demodulating weak current signals over short time windows of less than one period, and achieve a significantly lower standard deviation (6.7 mA) compared with the FFT method (15.6 mA) in the current range 0–0.306 A. The higher robustness against the background noise than the FFT method and the excellent repeatability of our demodulation method are also demonstrated through simulations. These results suggest that the proposed method will provide an effective way to improve the detection performances of FOCSs in fast dynamic measurements.

Fast-sweeping Langmuir probes: what happens to the I –V trace when sweeping frequency is higher than the ion plasma frequency?

Limited particle transit time is one of several limiting factors which determine the maximum temporal resolution of a Langmuir probe. In this work, we have revisited the known fast sweep Langmuir probe techniques in a uniform, quiescent multi-dipole confined hot cathode discharge with two operation scenarios: one in which the probe sweeping frequency f sweep is much lower than the ion plasma frequency f pi, another one where f sweep is much greater than f pi, respectively. This allows investigation into the effect of limited ion-motion on I–V traces. Serious distortions of I–V traces at high frequencies, previously claimed to be an ion-motion limitation effect, were not found unless shunt resistance is sufficiently high, despite a f sweep/f pi ratio of ∼3. On the other hand, evidences of sheath capacitance on the I–V traces have been observed. Distortions of I–V traces qualitatively agree with predictions of sheath capacitance response to the sweeping voltage. Additionally, techniques in fast sweep Langmuir probe are briefly discussed. The comparison between the high-speed dual Langmuir probe (HDLP) and the single probe setup shows that the capacitive response can be removed via subtracting a leakage current for the single probe setup almost as effectively as using the HDLP setup, but the HDLP setup does remain advantageous in its facilitation of better recovery of weak current signal commonly in low density plasma.

Research on Weak Current Detection System Based on Embedded System

In today’s society, the rapid development of science and technology requires the detection of weak current signals in many fields of scientific research. The research of its detection technology plays a very important role in promoting the development of science and technology. Considering that the weak current signal has strong background noise, it is easy to be submerged, the detection is difficult, and the professional requirement is strong. This research proposes a weak current detection system based on an embedded system that can detect nan oampere-level weak currents. The detection system is mainly composed of signal conversion amplifier filter circuit module, signal acquisition circuit, STM32, FPGA, upper computer and so on. Through experimental inspection, the researched detection system has the advantages of high accuracy and good stability.

Error Correction of Weak Current Measurement System Based on Wavelet Denoising and Generalized Regression Neural Network

Aiming at the problems that the weak current signal circuit is susceptible to noise interference and leakage current at the input terminal affects the measurement accuracy, a weak current measurement error correction scheme based on the combination of wavelet threshold denoising and generalized regression neural network (GRNN) was proposed. The scheme was applied to the error correction of multi-channel weak current measurement system based on the ADAS1134 chip: the wavelet threshold denoising was used to preprocess the original current data measured by the system and the current measurement value was corrected after the system measurement error correction model established with GRNN was constructed. Compared with the correction method based on least square method and back propagation neural network (BPNN), this method has many advantages such as high accuracy, anti-interference ability and strong generalization ability. The experimental results showed that RMSE=0.0911 nA, MAE=0.0354 nA, and MAPE=0.0078%, without increasing the complexity of the measurement circuit, which achieved the purpose of correcting the measurement error of the weak current measurement system.

Multi-Channel Eddy Current Detector Based on Virtual Instrument Technology and Self-Balancing Technology

In order to reduce the complexity of software and hardware design in multi-channel eddy current testing, a multi-channel real-time eddy current testing system based on lock-in amplifier technology and self- balancing technology is designed. The system uses graphical programming language platform (LabVIEW), Myrio1900 data acquisition control card and lock-in amplifier as key components. The lock-in amplifier adopts the lock-in technology to detect the amplitude and phase of the weak eddy current signal. The Myrio1900 card outputs multiple analog switch control signals and collects the amplitude component of the weak eddy current signal. The LabVIEW platform uses self-balancing technology to eliminate the imbalance of the bridge itself. The detection system realizes the real-time and reliable display of the amplitude and XY components of the 6-channel eddy current signal. Experimental results show that the designed system has a detection width of 56.00 mm at one time, and can detect artificial grooves with a covering layer of 2.90 mm. The artificial grooves have a width of 1.00 mm, a depth of 1.00 mm and a length of 50.00 mm. The system design process described in the article can be used as a reference for equipment developers and can also be used for educational purposes.