伏安法测电阻实验中量程转换对测量精度的影响

在伏安法测电阻的实验中,测量电阻伏安特性曲线时需要多次测量。为了充分利用电流表的测量精度,需要转换电流表量程,但与此同时电流表的内阻也随之改变。如何考虑量程改变带来的误差是本实验的一个重要问题。文章通过引入分段修正函数对测量数据进行处理,从而自洽地考虑了量程转换时电流表内阻改变对数据处理的影响,使数据处理方法更加合理,所得结果更加精确。     

将毫安表改装为大量程直流电流表的新方法

在电表改装实验中,如将毫安表改装成大量程直流电流表,由于分流电阻Rs的阻值较小,接触电阻和引线电阻已不可忽略,使得改装表达不到设计目标。通过采用四端引线连接分流电阻Rs,减小接触电阻和引线电阻的影响,结合开尔文电桥测低阻的方法测量分流电阻Rs,实现了大量程直流电流表改装。     

多量程电流表分流电阻的计算

多量程电流表分流电阻的计算卢梦克纪时佳管潇津（保定师专物理系河北保定０７１０５１）多量程电流表是测量中最常用的电磁仪表之一。在电磁学实验中，大部分高校安排了有关的设计实验，其关键性的问题是各档分流电阻的计算。采用传统的方法由于数据多、计算繁，很容易出...     

锻炼思维的电表改装问题

1 电压表、电流表的摆角与读数问题 1.1 电压表的摆角与读数问题 电压表是由一个电流表和一个电阻串联改装而成,电流表的摆角与电流成正比,因此电压表的摆角与流过内部电流表的电流成正比,电流越大摆角越大;电压表的读数为电流表的电压与串联电阻的电压之和,因此读数与摆角和量程都有关系.     

“并联半值法”测电流表内阻的误差分析

关于“把电流表改装为伏特表”的实验,《物理实验》杂志已登载过几篇文章,但都未对实验中测量电流表内阻所采用的“并联半值法”进行分析。我们利用清华大学附属中学物理实验室的条件,对这个实验,分别采用并联半值法、替代法对量程为5mA的电流表进行了测试比较,并做了一些探讨,供参考。     

测定电流表内阻的一种简便方法

测定电流表内阻的简便方法其电路如下图所示．图中G为内阻是r。的待测电流表，其量程为人；G；为已知量的另一电流表；R；与R。为两个可变电阻箱；K；、K。是两个电键；电路由电动势为。，内阻为厂的电源供电．当闭合电键K；、K。后，通过电路中干路的电流I；可从电流表G；上直     

在电学设计中培养学生的评价能力——从一道电学设计题说起

1缘起 近来测试卷中有这样一道题目：现有一满偏电流为50μA、内阻约为800～850Ω的59C2型小量程电流计G（表头）;另外可供选择的器材有电压表V（量程3V,内阻约为20kΩ）,电流表A1（量程200μA,内阻约为500Ω）,     

测定电表内阻的两种简单方法

测定电表内阻的两种简单方法游维（扬州化工学校２２５００２）在中专物理“电流表改装成电压表”和“扩大毫安表和伏特表的量程”这两组实验中都必须事先知道表头内阻的大小才能进行实验，而实际上有些电流表的表头内阻并没有标明，或电表的内阻太小，因而无法测量．为了...     

串并联电路在实际电路中的应用

中专物理教材(陕西省中专物理教材组编工科中专物理教材)对串联电路的分压作用和并联电路的分流作用在实际电路中的应用,分别以扩大电压表和电流表的量程为例加以说明.如果老师能够结合本校实验室所用的电压表、电流表的内部线路进行分析,不但能为学生分组实验提供有力的理论依据,还能使学生更好地理解中学教材中的相关内容:“电压表电阻很大,在电路中相当于开路;电流表电阻很小,在电路中相当于短路”.     

伏安法测量实验中系统误差的处理

1测量电路及实验原理在选择电流表内接电路时,设伏特表读数为U,电流表读数为I,测测量值Rx为:Rx=U/I=R+RA(1)可见,Rx>R图1电路图即:R=Rx-RA(2)式中R为待测电阻阻值,RA为电流表内阻。若能精确地提供RA的值,根据式(2)可准确计算阻值R。由于电流表内阻在不同的量程下不同,而且受实验环境的影响,因此,RA不能靠实验室提供,需要在实验中测量得到。如图1所示,合上K1、K2,在伏特表、电流表中读取数据:U1、U2、I,则:RA=(U1-U2)/I(3)事实上,这是测量微小电压降的方法。实验中,电流表的内阻较小,故电流表两端的电压降很小,用上述方法可以…     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.