## TRUE RMS MEASUREMENT

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KimAndersen
TwoWaves
Posts: 207
Joined: Fri Nov 30, 2012 2:53 pm
Location: Denmark

### TRUE RMS MEASUREMENT

Hi

I've a question regarding the use the "Add measurement" or how the calculations are done on the measurement "TRUE RMS".

My basic knowledge about "TRUE RMS" value of a perfect sinus AC signal is, that to get the "TRUE RMS" of a AC signal you must multiply the the positive peak value by 0.707.

When you look at this AC-signal, has it a peak to peak value of 1.163 volt and the half of this is 581.5 mV (peak value).

Multiply the peak value 581.5 mV with 0.707 and the result are 0.411 mV TRUE RMS.

But it is here I get confused, when I look at "Add Mesaurement" True RMS - it shows a TRUE RMS value of 351.1 mV which does not correspond with my calculation above.

Is the calculation inaccurate because of this AC signal not being a perfect sinus !!!.

Regards
Kim
TRUE RMS MEASUREMENT
TRUE_RMS_AC_VOLTAGE.psdata

STC
Banned
Posts: 790
Joined: Sun Sep 13, 2015 2:10 am

### Re: TRUE RMS MEASUREMENT

Hi Kim

Perhaps the Test and Measurement forum would be a better place to answer that question for you.
https://www.picotech.com/support/

Martyn
Pico Staff Member
Posts: 268
Joined: Thu Aug 11, 2011 7:43 am
Location: Cambridgeshire

### Re: TRUE RMS MEASUREMENT

For a triangle wave you need to multiply the peak by 1/SQRT(3) or 0.577 to get the correct value.

So as this wave is closer to a slightly rounded triangle wave, rather than a slightly triangular sine wave, the values you are seeing look correct to me.
Martyn
Technical Support Manager