Emad Alnasser

Bio: Emad Alnasser is an academic researcher from Islamic Azad University. The author has contributed to research in topics: Resistor & Operational amplifier. The author has an hindex of 4, co-authored 6 publications receiving 34 citations.

A Novel Low Output Offset Voltage Charge Amplifier for Piezoelectric Sensors

Abstract: 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.

A Novel Fully Analog Null Instrument for Resistive Wheatstone Bridge With a Single Resistive Sensor

Abstract: When high-speed measurements are not necessary, the Wheatstone bridge-based null measurement instruments surpass the Wheatstone Bridge-based instruments using deflection technique, due to the fact that the null method has some intrinsic advantages over the deflection method. In this particle, a fully analog method has been introduced in order to implement a null measurement instrument for a resistive Wheatstone bridge with a single resistive sensor. In order to implement the proposed circuit, only two operational amplifiers and some passive elements have been used. The proposed method can be constructed and implemented by discrete components without any special limitation. Since the suggested scheme has linear output, the required computation in order to measure and display the measurand is reduced dramatically. Finally, in order to evaluate the performance and usefulness of the proposed method, it has been tested experimentally as well as by using computer aided design software.

The Stability Analysis of a Biopotential Measurement System Equipped With Driven-Right-Leg and Shield-Driver Circuits

Abstract: One of the major problems encountered in biopotential recording is electromagnetic interference (EMI). The major source of EMI, in bioelectric measurement systems, is mains power, which is mainly coupled to the system through stray capacitances. The interference reduction is usually implemented using driven-right-leg (DRL) and shield-driver circuits, which are both feedback circuits. A variety of other auxiliary circuits may also be used for safety, ESD protection, and radio-frequency EMI filtering. Therefore, the system has great potential to become unstable. The general equivalent circuit of the bioelectric measurement system, which models the parasitic capacitive couplings between mains power and the system, is well known. The stability analysis of such systems is performed based on the simplified model, which is extracted from the general model by neglecting many electrical elements. In this paper, a simple and powerful approach is proposed to define the loop gain of the bioelectric measurement system explicitly and directly from the general model. Due to the nature of the proposed method, it can be implemented directly using computer-aided design software, to calculate the loop gain of the general model. Thus, the design process is improved significantly and many complex situations can be analyzed more easily. In particular, the proposed approach shows its advantages when the power line interference is coupled to the system through various capacitive paths. Another contribution of this paper is the stability analysis of isolated amplifier system, which is equipped with transconductance DRL and shield-driver circuits.

A Novel Fully Analog Signal Conditioning Circuit for Loss-Less Capacitive Sensor Estimation

Abstract: In this paper, a novel fully analog signal conditioning circuit for loss-less capacitive sensor estimation has been introduced. The proposed circuit employs a new form of the Wheatstone bridge in order to implement a novel null instrument. In contrast to the conventional ac Wheatstone bridge, all components of the used bridge, except capacitive sensor, are conventional resistors. Therefore, the used bridge is intrinsically unbalanced. In order to balance the bridge, a fully analog feedback network has been used. The main advantage of the proposed circuit over previous null instruments is that, it no longer requires controllable elements such as voltage controlled resistor in order to implement the feedback loop. In the proposed circuit, the bridge is balanced by using a simple and appropriate feedback network which is made by using only an operational amplifier and a resistor. The proposed circuit has been realized only by the use of Op-Amp-based amplifiers and a differential amplifier. Due to the simplicity of the architecture, it can be made by discrete and inexpensive parts. The suggested signal conditioning circuit is excited by a Sine voltage source and the phase difference between output and input voltages depends on the capacitive sensor value. The capacitive sensor estimation can be done by measuring the foresaid phase difference.

Lossy Integrator Readout Circuit With Active Bias Point

Abstract: 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.

Fast analytical techniques for electrical and electronic circuits: PWM switching dc-to-dc converters

Abstract: Preface 1. Introduction 2. Transfer functions 3. The extra element theorem 4. The N extra element theorem 5. Electronic negative feedback 6. High-frequency and microwave circuits 7. Passive filters 8. PWM switching DC-to-DC converters.

Effective Biopotential Signal Acquisition: Comparison of Different Shielded Drive Technologies

Abstract: Biopotential signals are mainly characterized by low amplitude and thus often distorted by extraneous interferences, such as power line interference in the recording environment and movement artifacts during the acquisition process. With the presence of such large-amplitude interferences, subsequent processing and analysis of the acquired signals becomes quite a challenging task that has been reported by many previous studies. A number of software-based filtering techniques have been proposed, with most of them being able to minimize the interferences but at the expense of distorting the useful components of the target signal. Therefore, this study proposes a hardware-based method that utilizes a shielded drive circuit to eliminate extraneous interferences on biopotential signal recordings, while also preserving all useful components of the target signal. The performance of the proposed method was evaluated by comparing the results with conventional hardware and software filtering methods in three different biopotential signal recording experiments (electrocardiogram (ECG), electro-oculogram (EOG), and electromyography (EMG)) on an ADS1299EEG-FE platform. The results showed that the proposed method could effectively suppress power line interference as well as its harmonic components, and it could also significantly eliminate the influence of unwanted electrode lead jitter interference. Findings from this study suggest that the proposed method may provide potential insight into high quality acquisition of different biopotential signals to greatly ease subsequent processing in various biomedical applications.

An Auto-Calibrated Resistive Measurement System With Low Noise Instrumentation ASIC

Abstract: Most of the resistive sensors have a large baseline resistor and a relatively small incremental change in the resistor value due to the measurand. A half-bridge-based versatile $\Delta R/R_{s}$ measurement system for a wide range of resistive sensors is reported in this article. A four-phase auto-calibration-based differential and ratiometric operation is used to compensate for the baseline resistance of the sensor and the mismatches due to the non-ideal circuit parameters. A low-noise application-specific current generator and low noise, high CMRR current-mode instrumentation amplifier is designed and fabricated in UMC 180-nm technology. A prototype board of the $\Delta R/R_{s}$ measurement system is developed and tested. The experimental results show that the proposed system is able to detect even smaller ppm level of about 72 ppm of $\Delta R/R_{s}$ for the base resistor $R_{s}$ value as high as 0.5 $\text{M}\Omega $ with a relative error of less than ±1%. The effect of the parasitic capacitors on the sensor response is also tested experimentally. Finally, the proposed system is tested with an in-house fabricated displacement sensor.

AN-C2V: An Auto-Nulling Bridge-Based Signal Conditioning Circuit for Leaky Capacitive Sensors

Abstract: This paper presents a fully analog auto-nulling bridge based capacitance-to-voltage (AN-C2V) converter circuit for measuring the capacitive component of the leaky capacitive sensors. The circuit utilizes an active bridge based architecture in which the quadrature components of the output are taken. An integrator-controller is used for auto-nulling. A unity gain, frequency-independent quadrature phase shift amplifier is designed for an accurate generation of 90° phase-shifted signal. Experiments conducted on the developed prototype demonstrate that the proposed AN-C2V system is able to estimate the sensor capacitor ranging from 47.2pF to 668.3pF with a maximum error of about ± 0.18% with respect to the commercial LCR meter. The effectiveness of the circuit is tested with the commercial leaky capacitive humidity sensor. The effect of leakage resistor, parasitic capacitor, frequency of excitation signal, and supply voltage is negligible on the final output, which results in a very robust and accurate solution for leaky capacitive sensors.

Methodology, Applications, and Challenges of WSN-IoT

Abstract: Wireless Sensor Network (WSN) is the trending area in Internet of Things (IoT) communication technology (WSN-IoT) The researchers have done a lot of contributions to an enhancement of sensor networks, but still, various research challenges are presently required to overcome Sensor nodes have varying properties, so the selection of sensor nodes to be done according to the applications of the WSN-IoT This framework presents a critical analysis of different types of sensors methodologies, applications, and research challenges with their literary works This framework will be helpful to interested researchers in identifying the requirement of sensor nodes while designing the applications of the sensor network