C Code to calculate RMS of sine-wave

[neuralc]

c code rms

Hi all,

Some one have a C code (for embedded) to calculate the RMS value of the sine-wave readed by an ADC of 8 bits?

ThX


NeuralC

 

[zastereo]

Hi neuralc,

It is very simple,

Consider your line frequency = 50.00 Hz

50.00 Hz = 20ms = 20000 us

for example if you grab sinewave sample @ 100us interval time you get 200 samples .

store in some buffer, your ADC is 8 bit so you need buffer of size
signed char adcbuf[200]

ok...

now do following

signed int rawrms ;
int rms ;

for( count = 0 ; count < 200 ; count++ )
{
rawrms += adcbuf[count] * adcbuf[count] ;
}

rms = rawrms / 200 ;
rms = sqrt(rms) ;

after squartrooting

you get actual rms of sinewave.


Regards.

Zastereo

 

[neuralc]

OK, Thx,

Like this we get the RMS for one cicle, but what about cicle to cicle, we make the average?


ThX

NeuralC