使用单片机测频的四种方法分析——兼谈等精度测频法的实现

本文论述了使用单片机测频的四种方法,即直接计数法、周期测频法、混合测频法和等精度测频法。通过误差分析指出,直接计数法适于高频测量,周期测频法适于低频测量。在此基础上,提出具有通频带测频性质的混合测频法,并给出其测频最大相对误差和最大误差频率点的表达式。关于等精度测频法,提出利用软件查询实现同步的方法。并论证其测频精度可达10~(-6)     

用测频法测量电容量

本文介绍了将电容量转换为频率,由单片机实施高精度测频并计算出电容值的测量方法.     

基于FPGA的智能高精度频率测量设计

为提高频率测试的精度和智能化程度,减少测试时间,提出一种基于FPGA的依据待测信号频率智能选择测试方案的频率测量方法。利用控制时钟和待测信号通过门电路延时产生的脉冲触发闸门信号,对待测信号频率精确测量进行理论分析、电路仿真以及FPGA硬件实现。仿真和测试结果表明:该方法能够依据待测信号自适应选择测试方案,提高测试精度,降低时间,很大程度上减少人工参与。     

基于CPLD的角速度波动率测量

以CPLD为核心的高速高精度的频率测量，不同于常用的测频法和测周期法。本文介绍的测频方法，不仅消除了常规测频法带来的误差，而且具有高集成度、高速、高可靠性的特点。     

一种低信噪比正弦信号高精度频率测量方法

在研究噪声对低信噪比正弦信号频率测量的影响、分析触发误差对多周期同步频率测量影响的基础上,提出了一种多-多周期同步频率测量方法,推导了频率测量计算公式和误差计算公式,并对两种测频方法的触发误差做了对比分析;最后给出了用STM32单片机实现多-多周期同步频率测量的方法。实验表明:该方法能有效压制噪声,提高低信噪比正弦信号频率测量精度。     

基于微机的频率测量系统研究

根据涡流传感器输出频率信号的特点，介绍了一种实用的基于微机的采用闸门时间修正的测频法，通过具体的硬、软件设计，实测了较高精度的频率测量。     

分频式计数型频率计的测频误差分析

本文主要分析以ＩＣＭ７２６１Ｄ计数模块为核心部件构成的１００ＭＨｚ数字频率计，因被测频率计十分频率产生夫落脉冲引起的误差，并总结了此种分频式计数频率计测频的总误差计算公式。     

高准确度智能测速系统的研制

研制了一种基于AT89C2051单片机系统的高准确度硬携式智能测速系统。该测速系统在高速时采和闸门时间自动调整的电子计数器测频法，在低速时采用被测信号周期自动调整的电子计数器测周法，实现了在宽量程范围内进行高准确主，实时快速测量。     

虚拟测频仪的设计与实现

介绍了一种基于LabVIEW的虚拟测频仪设计与实现。虚拟测频仪用于对现役装备的输出脉冲进行采集并给出其频率值。本文介绍了虚拟测频仪的硬件设计与软件编程实现，它采用LabVIEW编程，能同时测量多路通道．完成装备的各种试验和性能标定测试，测试数据自动存入数据库自动管理。测试精度和速度较高，适合工程使用。     

一个计算各类计数型频率计测频误差的新公式

本文推导总结出了分频式，倍频式，直接式计数型频率计测频误差的统一计算公式，欲使计数型频率计测频保差的计量规范化。     

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.     

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.     

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.     

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.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。     

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.