在频率标准与时钟评测中，阿伦方差为何比普通方差更适合刻画频率稳定度？
In frequency standards and clock characterization, why is the Allan variance more suitable than ordinary variance for frequency stability?
普通方差对含随机游走的频率数据会发散，而阿伦方差通过对相邻平均频率差的平方取平均，能有效抑制长期漂移并分离不同噪声类型（白噪声、闪烁噪声等）。它因此成为原子钟与振荡器稳定度评测的标准度量。
Ordinary variance diverges for frequency data with random walk, whereas the Allan variance averages the squared difference of adjacent mean frequencies, suppressing long-term drift and separating noise types (white, flicker, etc.). It is the standard metric for characterizing atomic clocks and oscillators.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Allan, Barnes,《A Modified "Allan Variance" with Increased Oscillator Characterization Ability》,Thirty Fifth Annual Frequency Control Symposium,1981 (DOI: 10.1109/freq.1981.200514)
Allan, Barnes, 'A Modified "Allan Variance" with Increased Oscillator Characterization Ability', Thirty Fifth Annual Frequency Control Symposium, 1981, DOI: 10.1109/freq.1981.200514
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1109/freq.1981.200514
#阿伦方差 #频率稳定度 #原子钟 #噪声类型
量值溯源链如何确保不同实验室测量结果的可比性与可信度？
How does a metrological traceability chain ensure comparability and credibility of measurements across laboratories?
溯源链将测量结果通过不间断的比较链逐级向上连接到国家或国际基准，每一步均有已知不确定度并附校准证书。由此任何实验室的量值都能回溯到同一 SI 基准，保证跨机构、跨国结果的可比与互认。
A traceability chain links a measurement through an unbroken sequence of comparisons up to a national or international standard, each step with known uncertainty and a calibration certificate. This lets any laboratory's value be traced back to the same SI reference, ensuring cross-institution and international comparability and mutual recognition.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#量值溯源 #校准 #计量基准 #不确定度
仪器的「分辨率」与「精度」是否为同一概念，应如何区分？
Are an instrument's resolution and accuracy the same concept, and how should they be distinguished?
分辨率指仪器能区分两个相近量值的最小间隔（灵敏度极限），精度（准确度）指测量值与真值的接近程度。高分辨率设备未必高精度，若未校准或存在系统误差，仍能分辨细微差异却整体偏离真值。
Resolution is the smallest interval an instrument can distinguish between two close values (a sensitivity limit), while accuracy is how close a measurement is to the true value. A high-resolution device need not be accurate; with poor calibration or systematic error it can resolve fine differences yet remain offset from truth.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#分辨率 #精度 #准确度 #仪器校准
2019年国际单位制（SI）重新定义后，基本单位如何改由基本常数定义？
After the 2019 redefinition of the SI, how are the base units defined through fundamental constants?
2019年起，SI的七个基本单位全部通过固定普朗克常数、玻尔兹曼常数、阿伏伽德罗常数、基本电荷等基本常数来定义，使单位不再依赖实物原器而具有普适稳定性。例如千克由 h、米由 c、秒由原子钟/光钟频率定义。
Since 2019 all seven SI base units are defined by fixing fundamental constants such as the Planck, Boltzmann, Avogadro, and elementary charge constants, freeing units from physical artifacts for universal stability. For example the kilogram is defined via h, the meter via c, and the second via atomic/optical clock frequencies.
难度 进阶 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录含书名，但缺版次 / 出版社 / 年份中的一部分，需编辑补全后才能做独立比对。
BIPM第26届国际计量大会决议1（2018），《国际单位制手册》第9版附录2
BIPM, 26th CGPM Resolution 1 (2018), Annex 2 of the SI Brochure, 9th edition
#国际单位制 #2019重新定义 #基本常数 #千克
测量不确定度的A类评定与B类评定在方法上有何区别？
How do Type A and Type B evaluations of measurement uncertainty differ in method?
A类评定通过对同一量的多次重复观测，用统计方法（如样本标准差）估计不确定度；B类评定则基于非统计信息，如仪器说明书、校准证书、以往数据或经验给出分布来评定。二者最终都归并为标准不确定度参与合成。
Type A evaluation estimates uncertainty from repeated observations of the same quantity using statistics such as the sample standard deviation; Type B uses non-statistical information like instrument specifications, calibration certificates, or prior data to assign a distribution. Both are converted into standard uncertainties for combination.
难度 进阶 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
国际计量局（BIPM）《测量不确定度表示指南》GUM
BIPM, Guide to the Expression of Uncertainty in Measurement (GUM)
#不确定度 #A类评定 #B类评定 #测量
间接测量量的不确定度如何通过误差传播公式由其分量的不确定度求得？
How is the uncertainty of an indirectly measured quantity obtained from its components via the error-propagation formula?
若 y = f(x₁,…,xₙ) 且各分量独立，则合成标准不确定度 u(y) = √[Σ (∂f/∂xᵢ)² u(xᵢ)²]。即对各分量不确定度按灵敏度系数（偏导数）加权后平方和开方，体现了不确定度沿函数关系的线性传递。
If y = f(x₁,…,xₙ) with independent components, the combined standard uncertainty is u(y) = √[Σ (∂f/∂xᵢ)² u(xᵢ)²]. Each component uncertainty is weighted by its sensitivity coefficient (partial derivative) and combined in quadrature, showing how uncertainty propagates linearly through the function.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：著录仅给书名，无版次与年份；同一书名常对应多个版次，不臆测具体版本。
国际计量局（BIPM）《测量不确定度表示指南》GUM
BIPM, Guide to the Expression of Uncertainty in Measurement (GUM)
#误差传播 #不确定度 #偏导数 #合成标准不确定度
系统误差与随机误差在来源、特征和处理方式上有何本质区别？
What are the essential differences between systematic and random errors in origin, behavior, and treatment?
随机误差来自不可预知的微小扰动，使重复测量围绕真值涨落，可用统计平均减小；系统误差来自仪器偏差、方法缺陷或环境偏移，使结果恒定或规律性地偏离，无法通过多次平均消除，必须靠校准与修正处理。
Random errors arise from unpredictable small disturbances, making repeated measurements fluctuate around the true value and reducible by statistical averaging; systematic errors come from instrument bias, method flaws, or environmental offsets, shifting results consistently and cannot be removed by averaging but require calibration and correction.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
程守洙 江之永,《普通物理学》第七版,高等教育出版社,2016
Cheng Shouzhu and Jiang Zhiyong, General Physics, 7th ed., Higher Education Press, 2016
独立核验依据 · Independent verification: 核验依据 2 ISBN 9787040429190（豆瓣书目条目: 普通物理学．上册）
#系统误差 #随机误差 #校准 #统计平均