waveforms RMS value is not all 0.707 why is that?

[stanleystan]

All these different types of waveforms RMS formula is not 0.707 why is that?

Only a sine waveform and rectified AC waveform is 0.707

a square waveform RMS is 1 , the RMS value is the same as the True value measurement, why is that?

Triangle waveform, rectangle waveform, ramp waveform, etc all have different RMS formulas , it's not 0.707

Without know the RMS formula for each waveform , is it easier just to use a DVM meter to measure the AC voltage to get the RMS voltage value?

Why would a tech need to know the RMS voltage? what good it is to know the RMS of a waveform?

 

[ljcox]

RMS means "Root Mean Square". It is calculated by using Calculus or by an approximation. So the value depends on the waveform. I'll post examples later.

An example of why a tech may need to know the RMS is:-
The RMS value allows you to calulate the power dissipation in a resistor.

 

[ljcox]

The attachments show how it is calculated using calculus.

It can be done by an approximate graphical method but it is complicated.

 

[Venkadesh_M]

It is totally a random thing and it is depend on the wave form. Your question is like why every one looking different.

But it is possible to have same factor between peak voltage and RMS voltage with diff waveforms.

 

[chuckey]

When a wave form has an RMS value of X volts, the heating effect is the same as X volts DC. As the heating effect is proportional to V squared, you have to first square the voltage then find their average then square root this value.
Frank