之前翻译了一篇：小白翻译第二篇：数字万用表工作原理（适合初学者） ，花了两天时间，查字典、翻译、码字、排版、整理、校对。。。不料被坛主老大当成是机器翻译，心里苦啊 ，不过回头想想，应该是自己翻译得太过生硬吧，好多专业术语小白还不太懂，现学现卖，再加上英汉表达习惯的不同不太好对应，使翻译出来的东西很晦涩。 今天又查了一些基础知识，关于RMS万用表和True RMS万用表的不同，比较浅显，适合像我一样的初学者对两种表的不同之处有个大概了解。篇幅较短，小翻一下，希望帮助到有需要的人，顺便涨涨经验，向赠表名额再迈进一步 。
What’s the Difference Between RMS and “True” RMS? RMS 与 True RMS万用表的区别 When you use a multimeter to measure an AC voltage or current, the reading on the meter is an "RMS" or "root mean square" reading. We sometimes call the RMS value the "effective value" of an AC voltage or current. By that we mean that the RMS value of an AC voltage or current has the same effect as a DC voltage or current of the same value. 当你使用万用表测量交流电压或电流时，万用表上的读数其实是RMS或者说是均方根（root mean square）。我们有时会把RMS称作交流电压或电流的有效值。这意味着具有某个RMS值的交流电压或电流会与具有相同该值的直流电压或电流宏观上具有完全相同的效果（等效）。
Let's consider an example. If I had a 10V DC power supply connected across a 10-ohm resistor, the power being dissipated by the resistor would be: P = V2/R = 100/10 = 10 W If I substitute a 10VRMS AC supply for the 10V DC supply, the power calculation would be exactly the same, and the resistor would dissipate 10W of power. The AC voltage is, however, constantly changing, so the 10W is an average over some period of time. At any particular point in time, the resistor will be dissipating more power, and at other times, less power. Assuming that the AC voltage supplied is a pure sine wave, the peak AC voltage will be 1.414 times the RMS voltage, or 14.14 V. Taking the inverse of that, you can see that the RMS value of a sinusoidal AC voltage is 0.707 times the peak value. 举例来说： 假设我有一个10V 直流电源接在一个10欧姆的电阻两端，那么电阻释放的热的功率应该计算如下： P = V2/R = 100/10 = 10 W 如果我将这个10V的直流电源替换成一个RMS电压值为10V的交流电源的话，功率的计算方法将与上式完全一样。电阻还将以10W的功率释放热能。然而，交流电压是在连续不断地变化着的，所以此时的10W只是一个在一段时间上的平均值。在某些特定时间点上，电阻的功率会大于10W，而在另一些时间点上，会小于10W。 假设交流电源的电压是一个纯正弦波，那么峰值电压将是RMS电压的1.414倍，即14.14V。反过来，我们可以看到，RMS值为峰值的0.707倍。 Most inexpensive meters use an averaging technique for determining the RMS reading of an AC voltage or current. This method gives you an accurate reading when you’re measuring an AC voltage with a sinusoidal waveform, but if the waveform of the AC voltage or current you’re trying to measure is not a pure sine wave, the reading will be inaccurate, usually low. Depending on the type of AC waveform, the reading might be up to 40% low. 大多数廉价万用表采用均值方法来决定交流电压或电流的RMS值。当你要测的交流电压或电流为正弦波时，这种方法可以测得准确的读数。然而，如果待测的交流电压或电流不是纯正弦波的话，读数将不准确，一般来说会偏低。读数会随着交流波型的不同而不同，最大可能会比真实值偏低40%。
If you need to measure the voltage or current of AC signals that are not pure sine waves, such as when you’re measuring the output of adjustable speed motor controls or adjustable heating controls, then you need a “true RMS” meter. A true RMS meter works by taking the square of the instantaneous value of the input voltage or current, averaging this value over time, and then displaying the square root of this average. 如果你要测非纯正弦波的交流电压或电流，如可调速的电机控制器或可调发热控制器的输出，那么你将需要一块真有效值（true RMS）万用表。 真有效值万用表工作流程： 采集输入端的电压或电流的瞬时值并将其平方->对得到的多个平方值依时间轴求均值->对得到的平均值取平方根得到真有效值（true RMS）->显示到屏幕上 The important thing to remember is that a “true RMS” meter will give you better readings. And, better readings will pay off in the long run, whether you’re making these measurements in the lab or out on the factory floor. 只需记住，真有效值万用表会给出更准确的读数。不论是实验室还是实地厂房，长远考虑，更准确的测量读数总会带来相应的回报。
原文链接：https://www.tester.co.uk/blog/electrical/multimeter-jargon-busters-true-rms Original author：admin of the website @ www.tester.co.uk 译者：rivrz @ 仪表爱好者 www.DT830.com
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发表于 2018-4-18 14:52:45
，果然是我翻译有问题，难怪坛主大人以为是机器翻译的，以后会努力改进
看来下回要在选材上多下点功夫了