危险环境中的数据采集与磁隔离传送

介绍了一种基于磁隔离的数据采集与传送方法.该方法适用于存在易燃易爆物质的场合,将输入、输出和电源电路实现完全三隔离,并且所有的电路无须接地.同时也介绍了磁隔离式检测栅与操作栅设计原理以及数据传输精度的测试方法.

Laser Doppler Vibrometer Without Directional Ambiguity Using Rectangular Phase Grating

The two-phase detection method for directional discrimination in laser Doppler measurements is discussed.The diffraction efficiency of a sin- gle period rectangular phase grating is analysed and a kind of back-scattered laser Doppler vibrometer without directional ambiguity using the single peri- od rectangular phase grating as the beam-combiner described.The principles of this kind of vibrometer are explained in detail,and some experimental re- sults are given.In this kind of vibrometer,the rectangular phase grating, without the zero diffracted order and even orders,is used to eliminate use- less stray light and to combine the useful signal light.Differential electronics is employed to reject signal noise.Therefore,the signal-to-noise ratio of Doppler signals and the measurement accuracy of the instrument are im- proved and the range of application is expanded.

Design of 10 Gbit/s burst-mode transimpedance preamplifier for PON systems

A 10 Gbit/s burst-mode preamplifier is designed for passive optical networks （PONs）. To achieve a high dynamic range and fast response, the circuit is DC coupled, and a feed-back type peak detector is designed to perform auto-gaincontrol and threshold extraction. Regulated cascade （RGC） architecture is exploited as the input stage to reduce the input impedance of the circuit and isolate the large parasitic capacitance including the photodiode capacitance from the determination pole, thus increasing the bandwidth. This preamplifier is implemented using the low-cost 0. 13 ixm CMOS technology. The die area is 425 μm × 475 μm and the total power dissipation is 23.4 mW. The test results indicate that the preamplifier can work at a speed from 1.25 to 10.312 5 Gbit/s, providing a high transimpedance gain of 64.0 dBΩ and a low gain of 54. 6 dBl2 with a dynamic input range of over 22.9 dB. The equivalent input noise current is 23. 4 pA/ Hz1/2. The proposed burst amplifier satisfies related specifications defined in 10G-EPON and XG-PON standards.

Numerical Simulation and Analysis of Bipolar Junction Photogate Transistor for CMOS Image Sensor

A new photodetector--bipolar junction photogate transistor is presented for CMOS image sensor and its analytical model is also established.With the technical parameter of the 0.6μm CMOS process,the bipolar junction photogate transistor is analyzed and simulated.The simulated results illustrate that the bipolar junction photogate transistor has the similar characteristics of the traditional photogate transistor.The photocurrent density of the bipolar junction photogate transistor increases exponentially with the incidence light power due to introducing the injection p+n junction.Its characteristic of blue response is rather improved compared to the traditional photogate transistor that benefits to increase the color photograph made up of the red,the green,and the blue.

应用于无滤波级D类音频功放的新型死区时间控制系统

设计实现了一种可集成于无滤波级D类音频功率放大器内部的新型死区时间控制系统,通过全新的死区控制系统以及辅助功率管栅级电压分段式驱动电路的采用,有效改善了功放的总谐波失真。采用0.35μm CMOS工艺实现了集成这种新型死区时间控制系统的2.1 W单声道无滤波级全差分D类音频功放。在3.0 V^5.5 V电源电压范围、增益设置为单位增益、8Ω喇叭负载下,输出功率1 W时,该D类音频功的总谐波失真(THD+N)为0.03%。

An all optical fiber gas sensor of NH3 and CO based on based on the spectral absorption and harmonic detection

An all optical fiber gas sensor is presented to detect the concentration of NH3 and CO. Based on the spectral absorption, The wideband light source is used to reflect two narrowband spectra by fiber grating of different duty. and piezoelectric ceramics to obtain narrowband output light. The high sensitivity detection can be measured from the second harmonic signal. The two narrowband spectra are corresponding to the absorption spectra of NH3 and CO. Concentration detection are realized by the detection of variety of light intensity. Sensitivity is proved and cost is reduced.

大功率铝氧化脉冲电源设计

介绍了用于铝氧化生产的叠加直流成分大功率脉冲电源的设计方法 ,在选用大功率器件时所需要考虑的问题 ,以及工业生产应用时 ,在设备可靠性方面所采取的技术措施和工艺措施。

FBG-based ultrasonic wave detection and acoustic emission linear location system

The ultrasonic (US) wave detection and an acoustic emission (AE) linear location system are proposed, which employ fiber Bragg gratings (FBGs) as US wave sensors. In the theoretical analysis, the FBG sensor response to longitudinal US wave is investigated. The result indicates that the FBG wavelength can be modulated as static case when the grating length is much shorter than US wavelength. The experimental results of standard sinusoidal and spindle wave test agree well with the generated signal. Further research using two FBGs for realizing linear location is also achieved. The maximum linear location error is obtained as less than 5 mm. FBG-based US wave sensor and AE linear location provide useful tools for specific requirements.

Fiber Laser Sensor Based on a Phase-Shifted Chirped Grating for Acoustic Sensing of Partial Discharges

Acoustic emission monitoring is often used in the diagnosis of electrical and mechanical incipient faults in the high voltage apparatus. Partial discharges are a major source of insulation failure in electric power transformers, and the differentiation from other sources of acoustic emission is of the utmost importance. This paper reports the development of a new sensor concept - a fiber laser sensor based on a phase-shifted chirped fiber grating - for the acoustic emission detection of incipient faults in oil-filled power transformers. These sensors can be placed in the inner surface of the transformer tank wall, not affecting the insulation integrity of the structure and improving fault detection and location. The performance of the sensing head is characterized and compared for different surrounding media： air, water, and oil. The results obtained indicate the feasibility of this sensing approach for the industrial development of practical solutions.

Research on Optical Fiber Flow Test Method With Non-Intrusion

In the field of oil well logging, real-time monitoring of the fluid flow parameter provides a scientific basis for oil and gas optimization exploration and increase in reservoir recovery, so a non-intrusive flow test method based on turbulent vibration was proposed. The specific length of the sensor fiber wound tightly around the outer wall of the pipe was connected with the optical fiber gratings at both ends, and the sensor fiber and the optical fiber gratings composed the flow sensing unit. The dynamic pressure was generated by the turbulence when fluid flows through the pipe, and the dynamic pressure resulted in the light phase shift of the sensor fiber. The phase information was demodulated by the fiber optic interferometer technology, time division multiplexing technology, and phase generated carrier modulation and demodulation techniques. The quadratic curve relationship between the phase change and flow rate was found by experimental data analysis, and the experiment confirmed the feasibility of the optical fiber flow test method with non-intrusion and achieved the real-time monitoring of the fluid flow.

Hydrogen Detection With FBG Sensor Technology for Disaster Prevention

Three fiber Bragg grating （FBG） sensors systems for hydrogen detection are presented using the classic Pd （palladium） coating technique （500nm） as the hydrogen sensitive film and titanium （Ti） as the adhesive layer with the etched cladding. These systems are compared and used for disaster environment prevention in hydrogen leakage environment where higher values than the normal are presented which increase the risk of explosion. With these systems, 0. 1% - 4% of the hydrogen volume concentration range in the volume ratio was detected and monitored experimentally in the test room with the very sensitive and stable value which reached 60pm/1% HE. In addition, a fast response time, about 6 s, was obtained with an advanced sensor.

Response Analysis of Ultrasonic Sensing System Based on Fiber Bragg Gratings of Different Lengths

In recent years, fiber Bragg gratings （FBGs） have been widely used in ultrasonic detection for practical structural health monitoring in light of its unique advantages over the conventional sensors. Although FBGs have been successfully tested in ultrasonic inspection, the effect of the grating length on the sensitivity of the FBG ultrasonic sensing system is yet to be analyzed. Hence, using the simulation model, the main influencing factor on the sensitivity of the ultrasonic sensing system with different lengths gratings was first investigated. In the following experiment, the ultrasonic responses of the sensing system with six different lengths FBGs were obtained, respectively. The theoretical analysis and the experimental results would be useful for sensitivity improvement of the FBG-based ultrasonic and acoustic emission sensing system.

Parameters optimization of π-phase-shifted long-period fiber grating for gas sensing

The gas-sensitive film coated π-phase-shifted long-period fiber grating(LPFG),consisting of two same long-period fiber gratings cascaded by a regular fiber with length of half of the grating period,is proposed for gas sensing.The sensitivity of the sensor is defined by the change rate of the transmission at specific wavelength with respect to the film refractive index.The qualitative and numerical analyses show that to get a high sensitivity,the optimal coupling strength of each long-period fiber grating is √2 π/4.With this coupling strength,the longer the grating is,the higher sensitivity the sensor has.By choosing appropriate grating period,a high sensitivity for the film with a certain refractive index and thickness can be attained.

Fiber Bragg Grating （FBG） Sensors Used in Coal Mines

The fiber Bragg grating （FBG） strain sensors were used for on-line monitoring of the stress variation of the lined wall in the gateway retained along the goaf of No. 3203 coal mining face in Dongtan Mine. The results showed that the FBG strain sensor with the wide measuring range could measure the stress variation accurately during the support process of the gateway retained along the goaf and could provide the basis to further optimize the support structure and to determine the support plan of the gateway retained along the goaf. The FBG micro-seismic sensors were used in Xinglong Mine to detect the micro-seismic signal. The signals were well received and analyzed to determine the location and energy level of the source of the micro-seismic event warning. The FBG sensors and detecting system show a significant potential for micro-seismic detection and geological disasters detection.

FBG Stress-Sensibilized Monitor for Railway Switch Pole On-Line Monitoring

The fiber Bragg grating （FBG） sensing technology is used to dynamically monitor multiple parameters of railway switch machine poles, including time of movement, direction and quantity of loading and locking force, and states of loading resistance. This paper presents the design and implementation of a railway switch pole strain on-line monitoring system based on the FBG stress-sensibilized monitor for a Siemens S700K switch machine. The ring shape FBG strain gauge and stress-sensibilized methods significantly increased the monitoring sensitivity. Installing approaches adapted the harsh environment in the railway application. The monitoring results showed the high sensitivity and high reliability of this monitoring system. This application provides a long-term and on-line detecting method which could meet railway switch condition monitoring demands of more than 100,000 switch machines in the country.