电光分析天平故障及修理

文章从六个方面阐述了TG328A、TG328B型电光分析天平常见故障的原因、调试及修理。     

TG328A型机械天平常见故障及调修

正0引言TG328A型机械加码天平准确度高,性能可靠,广泛应用于分析、化学等精密测量实验室。TG328A型机械天平组成部件较多,主要由框罩、机械挂砝码装置、横梁、立柱、制动系统、悬挂系统、光学读数系统、底座等组成。由于其结构精巧,微小的变化都会影响其使用,因此对使用者的要求较高。在日常实验中TG328A型机械天平往往会突发各种     

机械天平检定中的误差分析及处理

在机械天平检定和修理工作中,经常会碰到各种误差,现就目前广泛使用的TG328A型机械天平出现的较集中的现象分析如下:一、天平自身带来的误差由于天平的准确度较高,所以安装稍有一点不正确就可能引起天平的变化,产生较大的误差。如:天平放置不水平、支点刀承倾斜致使支点刀在摆动中两侧摩阻     

对TG328B天平的技术改进

半机械加码TG328B天平和全机械加码TG328A天平相比较，无论从结构本身，还是计量性能来看，相差都不大，现将不同处列表如下：     

TG528A、328B电光天平耳折的调整

在修理与使用 TG328A、328B 电光天平过程中,经常会遇到耳折的现象。所谓耳折,就是开启或关闭天平时,吊耳向一边倾斜的现象。造成耳折的原因是:边刀刃不在吊耳刀垫的假定中心线上,两边重量不等,向重的一边     

TG328型机械天平的常见故障及调修方法

介绍了TG328型机械天平的常见故障及调修方法,供相关人员参考。     

机械天平TG328A臂差的调修

机械天平TG328A是根据杠杆原理制成的,其两臂相等。等臂天平两臂不相等,在直接测量物品质量时就会出现误差．习惯上称这个误差为不等臂性误差,简称臂差或偏差。等臂天平要做到两臂完全相等是很难的,也是不客观的。因此．在国家计量检定规程中给出了法定允差,机械天平TG328A的允差为±3分度。     

TG328A型机械天平带针及跳针的调修方法

本文主要介绍了TG328A型机械天平带针及跳针的检查及调修方法。     

浅谈TG328A机械天平的几种常见故障与调修

本文介绍了TG328A机械天平的几种常见故障与调修,使分析天平称量操作更加准确、快速和科学合理。     

TG328型机械天平的快速安装与调试

本文对TG328型机械天平的快速安装步骤与调试方法进行了详细的阐述和分析。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.