RMS (Root mean square calculation) for analog input (0 to 3V)

prem shukla

Other Parts Discussed in Thread: CONTROLSUITE

Hello All,

I am using DSP F28335....trying to calculate RMS for sinusoidal input. First i am storing all the samples in one cycle than calculating RMS......, it's delaying the response. can u please suggest appropriate techniques which can give RMS within few samples.

Thanks,

Prem Prakash Shukla

over 13 years ago

0 Joy Philipz over 13 years ago

Expert 1500 points

RMS is calculated over a cycle. If the waveform has quarter cycle symmetry line sinusoid, may be you can calculate in quarter or half cycle. But it is an assumption, RMS stands for root means square value over a cycle.

Sample the waveform multiple times (say 128 samples per cycle for a 50Hz signal)

Square and add to sum_square at every sampling

On end of cycle (start of next cycle), find sqrt(sum_square/nsamples) & initialize sum_square..

What do you mean by delaying? RMS value will be updated at every period which is the best possible.

Cheers

Joy