These two formulas refer to the average voltage produced by a pwm output and a low pass filter.1) calculates the averaged dc voltage at the output of the filter2) calculates the power produced by the filtered voltage above since P=U^2/R, R being constant.If you apply the pwm voltage directly to the load (full voltage on, no voltage off) average power will be dutyCylce/255*P
So which formula should I use? The PWM output is directly applied to the load (which is a heater). The heater reaches the same temperature at a 25% 12v duty cycle as it does with a constant 6V. So to me that seems the correct formula, but I'm just confused why a volt meter would read 3V it seems to break Ohm's law,
A (normal, non TRMS) voltmeter in DC measurement mode will take a normal average of the input voltage. 12V*0.25 = 3V
.I have found them generally very poor at frequencies beyond 100Hz and anything other than sine wave.Not sure i would trust them even for ball park figures with a square wave.