📚 Calibration of Measuring Instruments | 测量仪器的校准
In AQA A-level Physics, calibration is a key practical skill and a core idea in the 'Measurements and their Errors' topic. An instrument is calibrated when its readings are compared with a known standard so that systematic differences can be found and corrected. Good calibration improves accuracy, supports valid conclusions, and helps you estimate the uncertainty in any quantity you measure.
在 AQA A-level 物理中，校准是一项关键的实验技能，也是 '测量及其误差' 主题的核心概念。仪器的校准是指将其读数与已知标准进行比较，从而发现并修正系统差异。良好的校准可以提高准确度、支持有效结论，并帮助你估计任何测量量的不确定度。
1. What is Calibration? | 什么是校准？
Calibration is the process of comparing an instrument's reading with a reference standard that has a known value and a very small uncertainty. The comparison can be direct, such as placing a standard mass on a balance, or indirect, such as using a known voltage to check a voltmeter.
校准是将仪器读数与已知数值且不确定度极小的参考标准进行比较的过程。比较可以是直接的，例如将标准质量放在天平上，也可以是间接的，例如使用已知电压检查电压表。
Calibration tells you how the instrument reading relates to the true value. It may produce a correction, a scale adjustment, or a calibration curve. It does not always make the instrument perfect, but it allows you to use it accurately.
校准告诉你仪器读数与真实值之间的关系。它可以产生修正值、刻度调整或校准曲线。它并不总能让仪器变得完美，但它能让你准确地使用仪器。
2. Why Calibration Matters | 校准为何重要
Calibration reduces systematic error. A calibrated instrument gives readings that are closer to the true value, so the accuracy of an experiment improves.
校准减少系统误差。经过校准的仪器给出的读数更接近真实值，因此实验的准确度得到提高。
Calibration also makes results comparable between different instruments, different days, and different laboratories. If every instrument is calibrated against the same standard, results can be trusted and reproduced.
校准还使不同仪器、不同日期和不同实验室之间的结果具有可比性。如果每台仪器都对照同一标准进行校准，结果就可信且可重复。
In AQA practical work, you should always state whether an instrument was calibrated before use, because this affects the evaluation of the method and the uncertainty quoted in the conclusion.
在 AQA 实验操作中，你应说明使用前仪器是否经过校准，因为这会影响对方法的评价以及结论中引用的不确定度。
3. Standards and Traceability | 标准与可追溯性
A standard is a device or material whose value is known with very high confidence. Examples include a standard mass, a standard resistor, a standard cell, or the fixed points of pure water.
标准是指其数值具有很高置信度的设备或材料。例子包括标准质量、标准电阻、标准电池或纯水的固定点。
Calibration is meaningful only if the standard itself can be traced back to national or international standards, such as those held by the National Physical Laboratory or defined in the SI system. This chain is called traceability.
只有标准本身可以追溯到国家或国际标准时，校准才有意义，例如由国家物理实验室保存或由国际单位制定义的标准。这条链称为可追溯性。
Without traceability, an instrument's calibration has no reliable reference. This is why AQA practical assessments often expect you to name the standard used, for example a 100 g standard mass or a 10.0 Ω standard resistor.
没有可追溯性，仪器的校准就没有可靠的参考。这就是为什么 AQA 实验评估通常要求你说出所用的标准，例如 100 g 标准质量或 10.0 Ω 标准电阻。
4. Systematic vs Random Errors | 系统误差与随机误差
Systematic errors shift every reading in the same way, perhaps by a constant amount or a constant fraction. Repeating a measurement does not reveal or remove a systematic error, but calibration can identify and correct it.
系统误差以相同方式影响每个读数，可能是恒定偏差或恒定比例。重复测量不能发现或消除系统误差，但校准可以识别并修正它。
Random errors scatter readings around the true value and can be reduced by taking repeat readings and finding a mean. Calibration does not remove random error, but it helps you assign a realistic uncertainty to the final result.
随机误差使读数在真实值附近分散，可以通过多次重复测量并取平均值来减小。校准不能消除随机误差，但能帮助你给出符合实际的不确定度。
A useful way to record the result of a calibration is a correction value. This is added to each measured reading to obtain the corrected value.
记录校准结果的一个有用方法是给出修正值。将修正值加到每个测量读数上即可得到修正后的值。
corrected value = measured value + correction
其中 correction = true value - measured value，由已知
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