# Explanation of different current/voltage types: RMS, Peak, Mean, DC, AC

Discussion in 'General Electronics Discussion' started by huynh213, Apr 12, 2016.

1. ### huynh213

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Apr 12, 2016
Hello,

As I use Digital Power Meter to capture current and voltage data out of my systems, I often see different types of current or voltage (Peak, Mean, DC, AC, RMS, RMN). Since I normally just use RMS or Peak for my calculation, I wonder if some of you can help me cover some other types so that I can have a better understanding of those.

I've been trying to Google a bit but couldn't find out any good sources that cover these material.

2. ### duke37

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Jan 9, 2011
DC Direct current, also used for voltage. This is where the voltage and current are constant and of only one polarity. The simplest to deal with.
AC Alternating voltage/current. This may apply to sine wave or any other wave shape where the current changes sine.
RMS Root Mean Square. This applies to AC and is the voltage/current that will give the same heating in a resistor as DC
Peak is the maximum voltage which is seen, it may be positive or negative.
Mean is the average of varying voltage/current.
RMN No idea.

Of you have an AC sine wave, then the peak is root 2 * RMS and the mean is RMS*0.9
Other wave forms may be vastly different.

3. ### davennModerator

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Sep 5, 2009
where the voltage is reasonably constant, the current can be varying continuously, it is still DC

you may want to reword that a little as well

4. ### duke37

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Jan 9, 2011
I looked up Wikipedia and they specify DC as one polarity and AC as repeatedly varying polarity.
I am used to circuits where the DC varies and can be considered a mixture of AC and DC.

Pehaps I shouldn't have tried to make a concise definition. Colin seems to think I do not know what I am talking about, maybe he is right.

5. ### dorke

2,342
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Jun 20, 2015
Welcome to EP.
Where have you seen that?

davenn likes this.
6. ### davennModerator

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Sep 5, 2009
it was really to point out that for DC the voltage is reasonably stable, say from a battery/PSU but the current can be fluctuating considerably
say the varying load of a DC electric motor

A changing DC is OK as long as it isn't regularly cyclic in its variations .... it's just called varying DC
if it is regularly cyclic .. a pure or complex sinewave for example, then it is an AC signal

making a clearer definition would have helped

And I wouldn't worry about what Colin says too much
he gives us mod's enough to worry about

your presence on Electronics Point is always appreciated, thankyou

Dave