Questions tagged [rms]

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

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Is my average power logic correct?

Original question I am trying to solve: This question is from "Fundamentals of Electric Circuits", 7th Edition from Sadiku and Alexander For this question, capacitors don't have average ...
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RCA RMS voltage

Searching the RCA phono input spec online does not garner any official documentation, probably due to the large number of voltage levels and power levels being used in commercial products. Looking at ...
lemon's user avatar
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2 answers
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Do industry true RMS volt meters use a transformer?

I'm trying to build a true RMS volt meter that plugs into my 120 RMS outlet. Since I want to do it safely, I'm using a very handy transformer (ZMPT101B AC voltage transformer module) that takes the ...
Krits's user avatar
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Does RMS value of AC signal depend on frequency?

The formula for voltage RMS is usually given as the peak value divided by the square root of 2. I feel like maybe I am missing something: how can two AC signals with same amplitude but different ...
Abdel Aleem's user avatar
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Pulsed current measurement and power factor calculation

I want to measure pulsed current in a 3-phase power meter application. I understand that the waveform will be random, as the current in question is the overall current consumed by different types of ...
Issam H's user avatar
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DC Load Current Vs RMS Load Current in single phase half wave rectifier

While solving a problem of a single wave half wave rectifier. using an "Ideal Diode" Given Details: Load Resistance - 1020 Ohms Supply - 230V 50Hz AC (Connected in series) To find : DC ...
Anirudh Srikanth's user avatar
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Create an expression for impedance on the form Z = R + jX

I'm supposed to create an expression for impedance on the form: $$Z = R + jX$$ I didn't know how to that so I looked at my teacher solution, but I don't really understand that either. The question ...
Ridertvis's user avatar
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Why does an AC Voltage reading on a DMM decrease as the frequency is increased?

I'm doing an assignment for a lab and I've found that frequency doesn't affect the voltage reading of an oscilloscope while it does for a DMM. Online, it says this is because an oscilloscope displays ...
Colonel Rabbynun's user avatar
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1 answer
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What assumptions are made by UL when they equate 30Vrms to 60Vdc for LVLE circuits?

UL defines Low Voltage Low Energy circuits as "A circuit involving an alternating current voltage of not more than 30 volts, rms (42.4 volts peak) or a direct current voltage of not more than 60 ...
jrive's user avatar
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How to calculate the average voltage and VRMS of a non sinusoidal waveform [duplicate]

I need to calculate the average voltage and VRMS of this. It's given that Vp=41V, Vn=-6V and T=13ms. I know the answer for the average voltage is 12.8V, but I can't find the formula that gets this ...
Parstoukas's user avatar
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A fully clamped sinusoidal wave has its RMS multiplied by the square root of 3. Is my textbook mistaken?

A fully clamped sinusoidal wave has its RMS multiplied by the square root of 3: Vo = 1.73Vi My textbook says that clamper circuits don't affect the Vpp and Vrms of an AC signal. Obviously, Vpp didn't ...
İbrahim İpek's user avatar
2 votes
1 answer
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Mistake in calculation of RMS current flyback primary switch node

I'm trying to calculate the RMS current of a flyback converters primary switch node. The Waveform is shown below: I'm okay with assuming it is a triangle wave with a duty cycle of 50%. The peak value ...
Antonio99200's user avatar
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2 answers
227 views

Y-connected 3-phase voltage source RMS voltage

If I have a three-phase Y-connected voltage source, and the voltages are \$V_{a} = V_{m}cos(\omega t)\$ \$V_{b} = V_{m}cos(\omega t-120^{\circ})\$ \$V_{c} = V_{m}cos(\omega t-240^{\circ})\$ At a ...
Kdwk's user avatar
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What does the RMS value of a DC current waveform represent?

I understand (or at least think I understand) the math and calculation of RMS values and that it generally is used for representing equivalent power of non-DC circuits, like typical sinusoidal AC ...
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Averaged first-order difference of Vout in QUCS

I am looking at a very simple LM317 voltage regulator circuit to drive a motor (represented by R3 in the diagram). I want to be able to sweep capacitor C2's capacitance and plot the mean 1st-order ...
TheDude's user avatar
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Peak detector circuit for AC RMS value

The peak detector circuit based on a precision rectifier with buffer allows to obtain the peak value. The RMS value in an AC circuit is obtained from: RMS = V peak / sqrt (2) = V peak * 0.7071 AC ...
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How do you calculate the average current of a square wave?

I'm working through the exercises of Art of Electronics and exercise 1.21 asks to calculate how big a fuse a circuit (full-wave rectifier using a center-tapped transformer) needs to be. The current is ...
Pieter van Ginkel's user avatar
3 votes
3 answers
396 views

Finding Vrms over time

The plot of voltage over time is given in below plot. As you can see, \$V_{max}=2v \text{ and } V_{min}=0v\$ \$t1=2ms, t2=8ms, t3=5ms, \text{ and period, } T = 15ms\$ Question is to find \$V_{rms}\$ ...
user97662's user avatar
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4 votes
1 answer
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Summing RMS values proof [duplicate]

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 ...
Arcadius's user avatar
5 votes
5 answers
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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 ...
Heneer's user avatar
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Phasor format vs time domain format question

I have a quick question regarding phasor format vs time domain format. Whenever we write in the phasor format, the magnitude that we use must be the RMS value for voltage/current, correct? Then we ...
RItaPoon's user avatar
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474 views

Why is this ideal diode bridge rectifier simulation in LTSpice not working as expected?

I'm trying to simulate a full wave bridge rectifier circuit with the capacitor filter. The alternating voltage supply is 30 V at 50 Hz. The peak value for the voltage across the load is 28.5 V. ...
Anay Chadha's user avatar
2 votes
3 answers
810 views

AC voltmeter circuit

I was searching a way to get the VRMS of an AC voltage. The main transformer drops down the 230 VAC to 15 VAC and with a potentiometer I'd like to display it on a DC digital voltmeter (the AC ...
philfs's user avatar
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Trying to design a circuit where it transforms its input voltage to a RMS output voltage

I'm trying to implement the RMS block in analog, i think doing only a peak detector would be way easier but perhaps the RMS would be more interesting. Other sources online suggest this: A squaring ...
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Usage of peak-to-peak voltage and RMS voltage

Why are RMS values and peak-to-peak voltages common in use? For example RMS voltages in the context of noise. I see especially for peak-to-peak voltage no practical usage. Why should I need more ...
bilaljo's user avatar
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Is the reference voltage for voltage control the RMS between the three phase voltages?

Suppose to provide voltage control with an AVR connected to a synchronous generator. A voltage reference is compared with the output terminal voltage of the generator, and the error between them is ...
Samuele Benito Di Gioia's user avatar
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Measuring AC current with a current transformer and ADC

I'm looking at using a current transformer (CT) to measure 50hz sinusoidal AC current with a microcontroller's ADC. Is there a way to measure the RMS or average of an AC signal with good response ...
Luke's user avatar
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Boost PFC power loss calcaulation

I am studying boost PFC topologies. I run into a question, how to calculate the CCM / CRM /DCM boost PFC power loss. I read the On semi document. I would like to derive the Diodes RMS current, but I ...
Jitter456's user avatar
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Measure power with multiple measurements

I want to measure the mean power draw of a Jetson Nano. I did this by using a digital multimeter and running the measurement 60 times with a fixed integration time of 0.3s. The result of each ...
HWilmer's user avatar
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3 answers
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Nominal or real AC/DC power supply values

I have three older AC/DC power supplies with these nominal values: Input 120 Vac, 0.3 A, 60 Hz Output 16 Vdc, 900 mA Input 120 Vac, ?, 60 Hz Output 16 Vdc, 1 A Input 120 Vac, 60 Hz, 4 W Output 9 Vdc, ...
Luis Salazar's user avatar
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Best way to decompose addition of waveforms?

I am searching for a way to decompose the exact components of additions of known waveforms. For example, lets say there is a waveform that is sum of multiple sinc functions. The sinc function's ...
Kangmin Bae's user avatar
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1 answer
292 views

Calculate power output of 3 phase generator - uneven sine wave

I am using this BLDC motor [https://uav-en.tmotor.com/html/2018/navigato_0402/52.html] as a generator. The device providing the mechanical drive turns the motor about half a turn and not at a linear ...
KevInSol's user avatar
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Connecting peak voltage, RMS, line-to-line and line-to-neutral

In EU the line-to-neutral voltage from a power outlet which is single phase (if I understand correctly) is 230V RMS and 50Hz. Then the line-to-line voltage (for the three-phase connection coming to ...
Clone's user avatar
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1 vote
3 answers
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How does the RMS voltage capture the time varying part in the conversion ratio of the half wave rectifier?

I am studying conversion ratio of a halfwave rectifier from here. It says that Conversion ratio (also called "rectification ratio", and confusingly, "efficiency") η is defined as ...
UserHuffmann's user avatar
2 votes
1 answer
197 views

Understanding stepper motor as generator Vs DC motor (RMS to equivalent DC)

I am using a stepper motor as a generator in a proof of concept experiment for something. The motor came from an old printer so do not have specs for it, but I believe it's unipolar. It has 5 wires, ...
KevInSol's user avatar
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1 answer
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How to get RMS voltage and frequency from datapoints read from an ADC?

I have an ADC that samples 4000 times per second or 0.25 ms interval per sample. I would like to extract the RMS and frequency value of the signal being read. How do oscilloscopes and multimeters do ...
DrakeJest's user avatar
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2 votes
2 answers
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Which theory do oscilloscopes or multimeters follow to measure RMS value?

For calculating RMS value , what I have found so far is that samples of a full cycle are taken then the ADC values are used to calculate RMS. Thus the RMS value stays independent of signal frequency. ...
Will Smith's user avatar
3 votes
3 answers
2k views

Circuit that converts sine wave to RMS voltage

How do I design a simple circuit that converts a sine wave to an RMS voltage? The input will be a sine wave and the output an RMS voltage. I know I will need an ADC, but not sure which one. I also ...
user361403's user avatar
0 votes
8 answers
710 views

Using 110 Vac incandescent light bulb at 220 Vac with a series diode

I have a 110 Vac incandescent light bulb but I need to use it in 220 Vac. If I add a diode in series with the bulb, the RMS power is the same as before but the peak value of voltage and current is ...
M Nasr's user avatar
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-1 votes
3 answers
286 views

How do I calculate an incomplete sinusoidal signal's average value and RMS value?

I couldn't be sure because there are parts with size 0 in the signal.
mike_lay944's user avatar
3 votes
2 answers
3k views

How do you convert dBm to Vrms?

I'm trying to convert dBm to Vrms. The formula for dBm is \$ dBm = 10 * log(P1 / P0) \$ where P0 = 1mW so \$ +13dBm = 20mW \$ If I convert this to a voltage using the formula \$ P = Vrms^2/R \$ ...
timsweeney7's user avatar
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3 answers
713 views

Calculating peak period jitter from datasheet that lists phase noise

The oscillator I plan on using list phase noise for a 20MHZ signal as: (100Hz) -124 dBc/Hz (1kHz) -140 dBc/Hz (10kHz) -148 dBc/Hz 100kHz -155 dBc/Hz (1MHz) -157 dBc/...
Matty's user avatar
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2 answers
144 views

Why is average power: the average of the voltage squared/resistance rather than the ((voltage average)^2)/resistance?

Regarding pulse waves specifically. So this should be especially simple. I see it written that $$\text{average power} = \text{average current} \times \text{average voltage}$$ which also equals $$ \...
ramose's user avatar
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0 votes
2 answers
188 views

RMS Current calculation from MCP3008

How to find RMS value of current from ADC value gets from CT??? . I have done like below Made a burden resistor and voltage divider circuit for CT MCP3008 connected with Jetson through SPI 5V to VDD ...
VIVEK A's user avatar
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1 answer
536 views

Average power when a periodic, non-sinusoidal waveform is applied across a resistor with a given voltage across it [closed]

If I have a resistor across which some voltage is provided and a periodic ( non-sinusoidal and non-zero) wave of current is given to the same resistor, then what would be the average power? Do I need ...
Ritu Halder's user avatar
2 votes
0 answers
530 views

Average power dissipated by a diode

EDIT: Added a picture with values and a better explanation. I need a little help over this calculation. I have to calculate the average power dissipated by a bootstrap diode (actually a MOSFET ...
KiDMiO's user avatar
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1 vote
4 answers
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How to measure power consumption of pulsed DC motor correctly?

I built a permanent magnet pulsed DC motor, and am trying to accurately measure power input, which proves to be harder than expected. The motor is pulsed with a 25% duty cycle square wave and powered ...
kregus's user avatar
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1 answer
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Finding RMS current of BLDC motor

I have a BLDC motor rated at 72V 1500W. I am working on an application that requires me to perform certain computations using the RMS current but I understand that I can only get the rated current ...
Atia's user avatar
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0 votes
4 answers
370 views

What's the RMS voltage of this asymmetric rectangle function?

I recorded this asymmetric rectangle function: I calculated the RMS voltage to be equal to the amplitude (4,10 V in this case) However when I measured this exact signal with a TrueRMS multimeter, it ...
Zciurus's user avatar
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0 votes
3 answers
2k views

Trapezoidal wave RMS value

I am calculating RMS value of trapezoidal wave. I found its formula like below: and at last the RMS value formula: u = 30degree or pi/6 --> especially pi/6 A = 12 When I calculate RMS value by ...
Piko's user avatar
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