RMS Voltage measurement of this waveform by AVR

[azadfalah]

Hello friends

How can I RMS Voltage measurement of this waveform by AVR ?



Thanks a lot

 

[andre_luis]

The RMS value is independent of the waveform, you just calculate the square root of the sum of the squares of each sample, just that.

 

[azadfalah]

but does this also work for a square wave?

If you could take an example

Thank You

 

[BigBoss]

It's a irregular waveform.Numerical Integration is necessary but it's pretty difficult to implement in uC .
Another solution is to use external RMS-DC Converter.It will be very practical and the DC value is proportional to RMS value of the waveform.

 

[azadfalah]

This does not require much precision

Is there a simple method with 10% error?

 

[andre_luis]

This does not require much precision

Is there a simple method with 10% error?

There is no precise answer to this question; in the end it will depend on the amount of samples per complete cycle of the waveform. Note that signals like the above one, having segments with high skew rate require a higher sampling rate.

 

[niciki]

Calculate FFT of this signal whatever method (on oscilloscope or on PC) and get fmax of this signal.
Your ADC must samples faster then 2*fmax.
Calculate squares of the samples then calculate mean value and at the end calculate root (LUT as possible implementation of the root function of desired resolution).