Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [rms]

Root Mean Square. Mathematical method to calculate effective value from an AC signal.

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Why V rms instead of V average?

I'm looking at an equation for average power in a signal $$ p_{avg} = \frac{1}{R} v_{rms}^2 $$ and wondering why it isn't $$ p_{avg} = \frac{1}{R} |v|_{avg}^2 $$
Rob N
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What is the difference between a multimeter with RMS and one with True RMS?

I am looking for multimeters. I am only a beginner in electronics, but I want to buy one that will be good enough for me for a while. I found a multimeter that measures True RMS, and another one that knows the same but without TRMS. (both made by…
Neinstein
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Mathematical proof that RMS voltage times RMS current gives mean power

I know this is true because I read it in a reputable source. I also understand intuitively that power is proportional to the square of voltage or current for a resistive load, and that the "S" in RMS is for "square". I am seeking a hard mathematical…
Phil Frost
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Strange measurements for Vrms in LTspice

For my experimental methods class (basically an intro to electronics) in university we had to simulate a circuit, which was nothing out of the ordinary, it just produces different sine waves of 2 volts peak to peak. However, what was interesting to…
Cristóbal Allendes
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Multimeter true RMS

I'm just getting started with electronics (arduinos and friends) and I would like to get a multimeter. As far as I can tell arduinos and any other logic chips and circuits I'm gonna be using are using DC power in the 3-12V range. Multimeters with…
adrianton3
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How can I tell if a particular multimeter measures AC with RMS or Average

I require a multimeter measuring RMS but unfortunately know little on the subject and am unable to tell which method one uses from it's description. Its states: MAX. Voltage between terminals & earth ground: 700V AC rms or 1000V DC Fuse…
Larry B
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Intuitive explanation for RMS voltage of discontinous sinewave

A sinewave with a peak voltage of 325.3V. The RMS voltage would be 230V Assumption1: If I were to run this AC sinewave through a resistor it would be the same power dissipated as running 230V DC through it. Assumption2: If I have a 230V DC signal…
Heneer
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What is the typical RMS noise of a lithium battery?

Take a typical CR2032 battery, if it is not discharging, what is the typical variation in voltage over a short period of time (eg a few seconds or minutes)?
John Smith
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Three phase rms voltage calculation

I am new in instrumentation and control. I am developing a hardware for a project and the following is my application. I have three phase stepped down voltages and stepped down currents entering my board. I can adjust the loads to be either purely…
John
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Half-wave rectifier and RMS value

I have built a half-wave rectifier with a 5V peak sine input, 1kHz. In theory the RMS of the output should be 5V/2 = 2.5V, but the oscilloscope only measures 2.01 V. What could be the reasons for such a difference? 0.5 V seems like a pretty…
Douglas Edward
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Summing RMS values proof

I have a simple circuit with two sources of different frequencies. I was tasked to get a voltage output across a component. I know for a fact that adding the derived voltage of both sources acting independently will yield the peak voltage when both…
Arcadius
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How do you differentiate between rms and peak voltage?

In the circuit above I've been asked to calculate the average power absorbed by the 10 Ω resistor. I managed to calculate a value for \$V_0=40\sqrt2\,\angle{-25}\$. But I'm not sure if this is peak or rms voltage. I've spoken to some people and…
Just Average
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Why are different RMS noise sources added in this way?

I'm wondering why noise sources are added such a way their RMS values are added in square root of sum of squares fashion. For instance if the RMS noise values from three sources are X,Y and Z, then the total noise is given as \$N =…
cm64
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BLDC Motor Constants: Why is my Kt and Ke different?

I'm new to working with motors. Reading up on BLDC theory, it is repeatedly said that in SI units, the Ke and Kt will be numerically equal. I downloaded the motor spec excel sheet of the T1101 motor by MTI. After choosing a particular winding and…
dumbpropnerd
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General PSpice and 555 timer question regarding precision

I have been experimenting with values recorded using a multimeter versus the voltages (RMS) simulated using capture. I simultaneously setup a circuit using a breadboard and drew exactly the same circuit in PSpice. I don't really have a particular…
atomSmasher
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