hi, i'm in the US and i'm wondering if i can still use the same IRMS value to calculate current? i changed the value of the current calibration to 2.3636 (i calibrated it to my meter), and i changed the apparent power to 118.3 (the value of the input voltage, also from my meter). so i just was wondering if the 1480 used in calcIrms was the same because i'm in the US.
Thanks!
Re: IRMS in US still the same?
"1480" is the number of samples you count over which you calculate the average. There are two considerations: Ideally you need a whole number of complete cycles. If you can't do that (and you can't because the mains frequency will vary slightly and so will your sample rate), then you make a guess at a reasonably big number and by making the fractional part of the cycle small in relation to the total number of cycles, you minimise the error. If you want to experiment to find the "best" number, you can use the millis( ) timer to measure the time that 1480 samples takes, then adjust the 1480 number so that the time is an integer multiple of 16.666 ms. Provided your mains supply remains at exactly 60 Hz and the crystal frequency, hence the millis( ) timer, is accurate then that should give a more accurate measure. You'll need to edit your emonLib to insert the timer.