Isolation Amplifier Research Articles

Error detection of isolation amplifiers in measurement systems

Error detection of isolation amplifiers in measurement systems

A Fully Integrated Low-Power Hall-Based Isolation Amplifier With IMR Greater Than 120 dB

A CMOS Hall-based fully integrated isolation amplifier for differential voltage sensing is presented in this work. The design is fabricated in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.35 \mu \text{m}$ </tex-math></inline-formula> CMOS process in which the high voltage (HV) side of the amplifier contains a coil driver while the low voltage (LV) side includes a Hall-effect sensor, low-noise amplifier, programmable-gain amplifier, filter, and chopper switches. Another Hall sensor performs the digital isolation using the on-off keying (OOK) technique for clock recovery. The introduced prototype achieves above 120 dB of isolation mode rejection (IMR) at 60 Hz and operates at a continuous isolation working voltage of 0.6 kV. It has also a maximum nonlinearity of 0.64 %, an input-referred offset of 1 mV, a 40 dB full-scale signal-to-noise ratio over a 40 kHz bandwidth, and a spurious-free dynamic range of 64 dB. The silicon area for each of the two separate dices employed for the HV and LV side of the isolation amplifier is 1 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> with a power consumption of 7.6 mW and 9.9 mW respectively. The achieved miniaturized size of the isolation components, as well as their significantly low-power consumption, ensure the suitability of the proposed isolation amplifier for multi-channel readout circuit applications.

Cascoded GaN half-bridge with 17 MHz wide-band galvanically isolated current sensor

A cascoded GaN half-bridge with a wide-band galvanically isolated current sensor is proposed. A 650 V depletion-mode GaN field-effect transistor is switched by a low-propagation-delay gate driver in active-mode. The standby and active modes are switched by a 25 V N-ch laterally diffused MOS (LDMOS). The current sensor uses the LDMOS as a shunt resistor, gm-cell-based sense amplifier and a mixer-based isolation amplifier for wider bandwidth. PVT variations of on-resistance of the current-detecting MOSFET are compensated using a reference MOSFET. A digital calibration loop across the isolation is formed to keep the current sensor gain constant within % across the whole temperature range. The wide-band current sensor can measure the power device switching current. In this study, a cascoded GaN half-bridge switching and inductor current sensing using low-side and high-side device current are demonstrated. The proposed techniques show the possibility of implementing a GaN half-bridge module with an isolated current sensor in a package.

A Small Footprint Digital Isolator Based on CMOS Integrated Hall-Effect Sensor

Digital isolators have been widely used to protect low voltage electronics as well as human safety from high voltage surges. However, conventional isolation links occupy large chip areas. In this article, a novel small-size on- chip digital isolator for medium-bitrate application based on a CMOS integrated Hall-effect sensor is reported. With the proposed approach, the area of the transmitter coil is reduced to lower than 50% of conventional transformers. The architecture reduces the chip area in isolation amplifiers, power control units, DC-DC converters, and clock recovery circuits. It allows the integration of multichannel isolators using two custom integrated circuits with no post-processing. The tested prototype achieves a data transfer rate of 20 Mbps with above 12 kV/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{s}$ </tex-math></inline-formula> of common-mode transient immunity (CMTI). It has 900 V of continuous isolation working voltage, 27 ns propagation delay, and consumes 2.3 mA of static current.

Electrospray Ionization Inside the Ion Inlet Tube: Multijet Mode Operation.

We investigated the electrospray ionization inside the narrow channel of the ion inlet tube. An insulating emitter capillary made of fused silica with a 0.2 mm outer diameter was inserted into the ion inlet tubes with a 0.5 and 0.6 mm inner diameter to aspirate all the charged droplets. A custom-made ion inlet tube with two side holes near its entrance is used to observe the spraying condition. The spray current is measured and monitored during the MS acquisition using isolation amplifiers. Because the emitter is cylindrically surrounded in close proximity by the metallic inner wall, it is difficult to obtain a stable and symmetric Taylor cone with its apex at the center of the emitter. Instead, a stable operation under a flow rate of 1-4 μL/min is found to be in the form of a multicone-jet mode with two or more Taylor cones anchoring around the rim of the emitter. The emitted charged droplet jets are dragged from hitting the wall by the fast-flowing air inside the inlet tube. Comparison with the typical cone-jet and multijet mode operated several millimeters outside the inlet capillary shows signal enhancements for protein standards.

A review of EEG acquisition, processing and application

As the study about the human body goes forward, some breakthrough in human biological signals is made, especially in EEG signal. At the same time, people are getting to know more about the benefits of EEG. Therefore, EEG research is enjoying a stronger demand around the world. Nowadays, EEG research is carried in several fields and different stages, such as the acquisition of EEG, the processing of EEG, energy recovery of EEG, etc. Scholars are mainly searching for behavioral and electrophysiology, neural network, multi-lead electroencephalogram, non-invasive brain imaging technology, etc. And the current research frontier and the main trend is the comprehensive study of brain function and disease at the molecular, cellular, and global levels and the understanding of the brain structure principle from the brain development process. In this review, three aspects are chosen to study: the processing of EEG, the acquisition of EEG and EEG application. Four EEG acquisition methods, five ways of EEG processing system and three patterns of application are introduced. EEG acquisition system comprises scalp electrodes, a signal isolation amplifier, an analog-to-digital converter, and a wireless transmission module. Low power consumption, small size and portability are the main directions. The research status and difficulties of suitable electrodes, high integration acquisition chip, and analysis algorithm are analyzed and predicted. Due to the rapid development of EEG signal processing, the application of EEG has developed from medical rehabilitation to driving safety, education assistance, and entertainment consumption.

A Galvanic Isolated Amplifier Based on CMOS Integrated Hall-Effect Sensors

A novel galvanic isolated amplifier based on CMOS integrated Hall sensors is presented in this paper. Two serially connected Hall-effect sensors are integrated along with their instrumentation amplifiers using the TSMC 65nm process. A printed-circuit board is employed to validate the proposed isolation amplifier by assembling the chip with chopper modulator, coil driver, miniature coil, variable gain amplifier, and anti-aliasing filter. Because of the miniaturized size of isolation components, this approach can be packaged in chip for industrial applications. This solution replaces the need of bulky/frequency dependent current transformers, complex isolation amplifiers with embedded analog to digital converters, and allows proposed sensors to be used in voltage and current sensing applications. The introduced prototype achieves an input referred offset of 1 mV, 50 dB full-scale signal-to-noise ratio in a 10 kHz bandwidth, and spurious-free dynamic range of 53 dB, while satisfying continuous isolation working voltage of 550 V.

Development of PC based automation of ion beam analysis and ion implantation experiments

This paper presents the details of a personal computer (PC) based automation of ion beam analysis and ion implantation experimental setup that has been developed and implemented in a 1.7 MV Tandetron accelerator. Hardware and software of the PC automated system were designed to automate multiple sample ion implantation, standard Rutherford Backscattering spectrometry (RBS), and High resolution Rutherford Backscattering spectrometry (Hi-RBS) experiments. The system uses in-house developed signal conditioning circuitry, isolation amplifiers, and transistor drivers along with cost-effective and off-the-shelf commercial components like a general purpose, multifunction data acquisition card, etc. A five axis goniometer is used for handling multiple samples and their automatic positioning according to the commands from the PC over RS232 interface. Key tasks carried out in the automation of system include control and mesurement of ion beam fluence, selection of backscattered particles through screening of their energies by controlling a set of +/−25 kV and −3 kV high voltage power supplies, controlled collection of backscattered yield using single and multi channel analysers, controlling the region-of-interest windows in the energy spectra and the cumulative counts in them. Controlling the position of the samples and facilitating the experiments on multiple samples, online display of energy spectra and its auto storage, and vacuum interlocking are also automatically done. This PC based setup has been automated using a windows based LabVIEW software making it easy to port the set up between different computer operating systems apart from achieving many other advantages like quick and easy development of versatile, multi-purpose, and user friendly graphical interface. Extensive tests carried out on the hardware established correct functioning of various modules of the hardware. The 0–10 V control inputs applied to the +/−25 kV and −3 kV high voltage power supplies were tested and seen providing an <0.1% accuracy, <0.05% linearity, very low drift of 50 ppm, 0.01% precision, and <1mv rms output noise. The software modules have been tested to check independent control and monitoring the irradiated dose, energy to voltage conversion, the multi channel analyser control in addition to other tasks such as computing the region-of-interest counts. The fluence computed from the pulse counts from the ion beam current integrator and the actual fluence were found to be matching within 0.1%. The vacuum interlocking scheme was tested covering a range of 10−5 mbar to 10−9 mbar. Hi-RBS was carried out on a 3 nm thick Ag film grown on Si substrate using 0.3 MeV H+ ion beam over a backscattered energy range of 10–300 keV for a fixed ion fluence 2 × 1012 ions/cm2 at each energy. The recorded spectrum showed well separated Si edge and Ag peaks. The energy resolution is calculated to be 1.2 keV and a relative energy resolution (ΔE/E) of ∼0.4% is obtained.

A Wide-Band High-Resolution Transmitter for Optical Isolation Amplifier

A wide-band and high-resolution transmitter of optical isolation amplifier is proposed for switching power supply isolation and servo motor drive applications. The transmitter is based on the chopper-stabilized technique and sigma delta modulator. A built-in common-mode voltage circuit of switched capacitor is proposed to ensure the stability of input DC common mode. Meanwhile, the feedback capacitor is used to improve the driving ability, which helps to avoid a buffer with large input swing. The circuit is tapeout with GF CMOS 0.18 μm 1P6M process with 5 V power supply. The test results show that in 5 V supply voltage, the input swing of transmitter is 2 V and the effective signal bandwidth is 110 kHz. And the output resolution achieves 11 bit.

Two-electrode-pair electrocardiogram with no common ground between two pairs.

An electrocardiogram (ECG) records the electrical activity of the heart using two electrodes to detect electrophysiological signals from the organ and one reference electrode (typically attached to the right leg) as the reference potential. An inconvenience of the three electrodes is that the grounds of the amplifiers are interconnected all over the body. To address this inconvenience, this paper proposes a two-electrode ECG measurement method with common electrodes instead of the reference electrode of the right leg. The power supply and the ground of the amplifier supplying the two electrode pairs are not connected and independent. Pasted on the skin with the body as the reference potential, both electrodes detect electrophysiological signals, transmitting the signals through two isolation amplifiers to an instrumentation amplifier filter and generating ECG waveforms. Both previous-stage electrode amplifier circuits of the isolation amplifiers used their respective power supplies; their grounds were unconnected to those of the power supplies. Similarly, the next-stage electrode amplifiers used their respective power supplies, with their grounds unconnected to those of the power supplies. Experiments yielded ECG signal waveforms in Leads I to III, with that of Lead I most resembling the waveforms of conventional reference electrodes. This method can be used to develop wireless ECG devices and portable ECG devices that eliminate the need for wiring to facilitate ECG measurement.

A Noninvasive Online Monitoring Method of Output Capacitor's C and ESR for DCM Flyback Converter

In a power electronics system, an electrolytic capacitor (E-Cap) is widely used, whose performance degradation can be reflected by the change of capacitance ( C ) and equivalent series resistance (ESR). This paper proposes a new online C and ESR monitoring scheme for the output electrolytic capacitor in a discontinuous conduction mode (DCM) flyback converter. The mathematical relationship between the instantaneous capacitor voltage and other parameters is analyzed and then the scheme of undetermined coefficients based on the multiple-spot sampling and least square method is further proposed. In addition, considering the particularity of high ripple current and the resultant voltage ripple variation range, especially with the temperature, an inverse ripple voltage isolation amplifier with variable amplification factor and negative voltage elimination is put forward so as to make digital signal processor identify the temperature change easily. The proposed scheme is noninvasive as only voltage signals need to be sampled and no current sensor is necessary. A prototype is built and the experiments are made to verify the effectiveness of the proposed method, from which the data are in accordance with the results measured by an LCR meter.

An Approach for High Voltage Battery Voltage Sensing of Plug-In Hybrids and Battery Electric Vehicle

This paper proposes an approach for measuring voltage of high voltage(HV) battery of plug-in hybrid electric vehicle(PHEV) and battery electric vehicle(BEV). The proposed methods use isolation resistor and isolation amplifier in order to measure high voltage which should be electrically separated fr...

Development of a Digital Quench Detection System for Nb3Sn Magnets and First Measurements on Prototype Magnets

The High Luminosity upgrade for the Large Hadron Collider LHC (HL-LHC) requires new Nb3Sn superconducting magnets and it triggers a development of novel hardware for the quench detection system (QDS) based on a field programmable gate array (FPGA) digital platform and a number of individually isolated analogue front-ends. Galvanic insulation has been implemented downstream the analogue to digital convertors to eliminate a usage of analogue isolation amplifiers. This concept was already successfully implemented in the current LHC QDS system, however the mitigation of new phenomena inside Nb3Sn materials required development of a new generation of QDS. The newly developed universal QDS offers flexibility of firmware defined architecture. Adopted prototype driven strategy includes thorough characterization of the analogue front-ends in the laboratory and prototype unit measurements performed on HL-LHC magnet prototypes at CERN's superconducting magnet test facility SM18. The tests also reveal the characteristics of the magnets as well as the measurement electronics at an early stage. The test results are used to optimize the analogue input stages as well as the digital signal processing within the FPGA. The preliminary test results are presented and focus is given to the measurement and studies of the so-called “flux jumps” to mitigate the effects of these voltage perturbations in the QDS.

Experimental industrial signal acquisition board in a large scientific device

In order to measure the industrial signal of neutrino experiment, a set of general-purpose industrial data acquisition board has been designed. It includes the function of switch signal input and output, and the function of analog signal input. The main components are signal isolation amplifier and filter circuit, ADC circuit, microcomputer systems and isolated communication interface circuit. Through the practical experiments, it shows that the system is flexible, reliable, convenient and economical, and the system has characters of high definition and strong anti-interference ability. Thus, the system fully meets the design requirements.

Effects of gamma-ray irradiation on electronic and non-electronic equipment of Large Helical Device

In a deuterium operation on the Large Helical Device, the measurement and control equipment placed in the torus hall must survive under an environment of radiation. To study the effects of gamma-ray irradiation on the equipment, an irradiation experiment is performed at the Cobalt-60 irradiation facility of Nagoya University. Transient and permanent effects on a personal computer, media converters, programmable logic controllers, isolation amplifiers, a web camera, optical flow meters, and water sealing gaskets are experimentally surveyed. Transient noise appears on the web camera. Offset of the signal increases with an increase of the integrated dose on the programmable logic controller. The DeviceNet module on the programmable logic controller is broken at the integrated dose of 72 Gy, which is the expected range of the integrated dose of the torus hall. The other equipment can survive under the gamma-ray field in the torus hall.

Voltage-induced frequency drift correction in fourier transform electrostatic linear ion trap mass spectrometry using mirror-switching

Ion capture from an external nano-electrospray ionization source in a Fourier transform electrostatic linear ion trap has been effected by mirror-switching. This capture method can suffer from time-dependent frequency shifts in the measured ion motion, which compromises mass resolution when using Fourier transform techniques for mass determination. This phenomenon was determined to be a result of the transient voltage recovery of the power supplies used for mirror-switching in response to a pulsed capacitive load, for which several examples are shown. A circuit, based on the AD210AN isolation amplifier, was fabricated to compensate for the voltage perturbation induced by mirror-switching by superimposing the inverted perturbation to the electric field of the opposing reflectron. In doing so, the dependence of the ions path length and frequency on the power supply output was greatly reduced throughout data acquisition. With this circuit enabled, no frequency shifts were observed in the mass spectrum when using mirror-switching, and thus pressure-limited theoretical resolutions were achieved. For example, an absorption mode resolving power of greater than 50,000M/ΔM FWHM was observed for iodide (m/z 126.9) at a transient length of 300 milliseconds. The use of mirror-switching led to a much greater m/z range than in-trap potential lift for a single ion injection which is demonstrated via simulation and experimental results. This correction method is simple to implement and does not require user intervention once properly tuned.

Wide-band optical coupling isolation amplifier for the Joint TEXT tokamak

Isolation amplifiers are widely used on Joint TEXT (J-TEXT) tokamak. Designing an isolation amplifier with a minimum bandwidth of 1MHz is necessary because the sampling rate of the signals of Langmuir probe diagnostic systems is 2MHz. A wide-band optical coupling isolation amplifier was proposed in this study. Experimental results show that the isolation amplifier can transmit an analog signal from DC to 2.7MHz with good linearity. The propagation delay of the circuit is within 142ns. The effects of the compensation capacitor on frequency characteristics of the isolation amplifier were determined through simulation. A mathematical model of the circuit was established, with several parasitic parameters considered. The linearity and frequency characteristics of the circuit were studied by combining theoretical analysis, simulation and testing. The availability of the presented isolation amplifier was verified in the Langmuir probe floating potential measurement system on J-TEXT.

Compact, battery powered, wireless digitizers for in situ data acquisitions in the sino-united spherical tokamak.

Potential isolation and long cable drive are very important in acquiring certain signals from tokamak diagnostics. Compact, battery powered, wireless digitizers for in situ data acquisition have been developed and routinely used in the sino-united spherical tokamak to solve the problems of isolation and long cables. The wireless digitizers utilize the integrated analog to digital converters and the static random access memory of microcontrollers but transfer data wirelessly. They consist of simple and concise circuits but have considerable performances of 12-16 bit in resolution and 500-1000 kS/s in sample rate. Wireless triggering and energy saving are two major challenges of the wireless digitizers. Wireless transceivers in the data link layer are used as trigger and can reduce the trigger jitters to be smaller than 1 μs. In order to reduce the energy consumption, the wireless digitizers are waken only when the tokamak is about to discharge. After discharges, they turn to a periodic checking mode with current consumption smaller than 200 μA. Because of low duty cycle, the wireless digitizers have a battery life of up to four weeks. In general, the wireless digitizers have better performance than normal isolation amplifiers and can greatly simplify the cable connections. They are very suitable for the data acquisition of dangerous and/or susceptible analog signals in tokamaks.

Design of a Charge Drive for Reducing Hysteresis in a Piezoelectric Bimorph Actuator

This paper describes the design of a charge drive for reducing the hysteresis exhibited by a piezoelectric bimorph bender. Existing charge drive circuits cannot be directly applied to bimorph benders since they share a common electrode. In this paper, a new charge drive circuit and electrical configuration are implemented that allows commonly available piezoelectric bimorphs to be linearized. This circuit consists of four major components, including, a high voltage amplifier, a differential amplifier, a piezoelectric load, and a PI feedback controller. An isolation amplifier was used to achieve a differential amplifier with a high common-mode rejection ratio. The charge drive was tested by driving a series poled three layer bimorph bender. The experiment showed a significant improvement to the hysteresis of the bender when compared to a typical voltage drive. This paper has identified an alternative Feedback method to improve the ac hysteresis performance of a piezoelectric bender by using a charge drive.

인버터의 직류링크 전압 검출 및 궤환을 위한 절연앰프 회로

This study proposes an isolation amplifier circuit for the sensing and feedback of inverter DC-link voltage, which is inevitable for the precise control of inverter output voltage. The isolation amplifier consists of a pulse-width modulator and a pulse transformer with dual secondary windings. The accuracy of the proposed circuit depends on the precise matching of filter parameters in dual secondary circuits. The influences of parameter inaccuracy on the amplifier performances are analyzed. A modified circuit is proposed to reduce the dependency on filter parameters. The validity of the proposed method is verified through simulation and experiment.