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How to conver RMS to Peak-to-Peak??

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Styx

Active Member
that is only true for sinus waveforms about zero
 

k7elp60

Active Member
conberting rms to peak-to-peak

multiply rms by 2.828 = peak-to-peak
 

Roff

Well-Known Member
Re: conberting rms to peak-to-peak

k7elp60 said:
multiply rms by 2.828 = peak-to-peak
But as Styx said, only for sine waves that have no DC component.
 

ljcox

Well-Known Member
Re: conberting rms to peak-to-peak

Ron H said:
k7elp60 said:
multiply rms by 2.828 = peak-to-peak
But as Styx said, only for sine waves that have no DC component.

True, but is is easy to subract the DC component. But, to find the RMS of a non sinusoidal waveform, you need to do some Calculus.

Len
 

Dean Huster

Well-Known Member
Truncated Approximations

After 20+ years of teaching electronics and the advent of inexpensive scientific calculators, I don't much like the idea of folks using truncated approximations for constants. It galls me to watch a student enter 3.14 on a calculator (4 keystrokes) rather than hitting the "pi" key (1 keystroke) for 10 digits of precision; or 1.414 (5 keystrokes) rather than 2 & the sqr-rt key (2 keystrokes) for 10 digits of precision. Granted, you don't need 10 digits of precision for any of these calculations but the time saved alone is worth using the simpler calculator entries.

Besides that, there's less to remember. 3.14159.... is harder to remember than the symbol on the "pi" key; if you need 0.707...., just do [2][sqr rt][1/x] for the full 10 digits of precision -- that's still 2 keystrokes shorter than entering 0.707!

In addition, you'll make fewer errors. I don't know how many times that I've seen a number entered where the decimal point didn't "catch", throwing the calculation off by several decades.

It took me too long to quit making students mule-haul all of their math just for the sake of the math section of the electronic course with the reason that "you'll know more easily if you've made a calculator error". I discovered that I can drive that point home without forcing students to add 1.47 x 10^-6 and 0.00349 x 10^2 by hand.

My time has been better spent teaching the students that dividing 1.81 by 3.0 does not give you an answer with 10 digits of precision even if the calculator does provide 10.

Dean
 

Styx

Active Member
Re: conberting rms to peak-to-peak

ljcox said:
Ron H said:
k7elp60 said:
multiply rms by 2.828 = peak-to-peak
But as Styx said, only for sine waves that have no DC component.

True, but is is easy to subract the DC component. But, to find the RMS of a non sinusoidal waveform, you need to do some Calculus.

Len

But.. since you are normally told only the RMS value how do you know the DC offset that is part of the rms value?

and very true ONLY revert to a number at the lastest stage of a caluculation 1.414 might be a decent approx to sqrt(2) but for statest 1.414 isnt (as stated) and it is easier (and less easy to get lost) by writing √2
 

ljcox

Well-Known Member
Re: conberting rms to peak-to-peak

Styx said:
ljcox said:
Ron H said:
k7elp60 said:
multiply rms by 2.828 = peak-to-peak
But as Styx said, only for sine waves that have no DC component.

True, but is is easy to subract the DC component. But, to find the RMS of a non sinusoidal waveform, you need to do some Calculus.

Len

But.. since you are normally told only the RMS value how do you know the DC offset that is part of the rms value?

and very true ONLY revert to a number at the lastest stage of a caluculation 1.414 might be a decent approx to sqrt(2) but for statest 1.414 isnt (as stated) and it is easier (and less easy to get lost) by writing √2
Yes, it depends on what you know. eg. if told that the valtage is say 10 Volt RMS, you would not know what waveform it referred to.

I don't understand your second para.

Len
 

pebe

Member
I think most people would assume that a stated RMS value refered to a sinusoidal waveform with no DC component, unless some information was given to imply otherwise. Or am I wrong?
 

udi_hakim

New Member
Re: Truncated Approximations

Dean Huster said:
After 20+ years of teaching electronics and the advent of inexpensive scientific calculators, I don't much like the idea of folks using truncated approximations for constants. It galls me to watch a student enter 3.14 on a calculator (4 keystrokes) rather than hitting the "pi" key (1 keystroke) for 10 digits of precision; or 1.414 (5 keystrokes) rather than 2 & the sqr-rt key (2 keystrokes) for 10 digits of precision. Granted, you don't need 10 digits of precision for any of these calculations but the time saved alone is worth using the simpler calculator entries.

Besides that, there's less to remember. 3.14159.... is harder to remember than the symbol on the "pi" key; if you need 0.707...., just do [2][sqr rt][1/x] for the full 10 digits of precision -- that's still 2 keystrokes shorter than entering 0.707!

In addition, you'll make fewer errors. I don't know how many times that I've seen a number entered where the decimal point didn't "catch", throwing the calculation off by several decades.

It took me too long to quit making students mule-haul all of their math just for the sake of the math section of the electronic course with the reason that "you'll know more easily if you've made a calculator error". I discovered that I can drive that point home without forcing students to add 1.47 x 10^-6 and 0.00349 x 10^2 by hand.

My time has been better spent teaching the students that dividing 1.81 by 3.0 does not give you an answer with 10 digits of precision even if the calculator does provide 10.

Dean

Each and every math teacher i have had during school didn't know how to make a pi on the scientific caclulator (shift + EXP) so they just told us to use 3.14.
I think that the problem starts from the old skool (usually aged 70+ :twisted: ) teachers that can't operate calculator...
 
ok

If your taking RMS and turning it to peak and you want some simple steps.
Rms/.707=Peak
Peakx2=PeaktoPeak.
There plane and simple. I'm in an college electronics course and the instructor tells us not to take it down below the 10 thousandths so there will be a bit of variation from different peoples answers. Each person rounds a little differently or goes to a different decimal place.
 
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