Alternate Current 50 Hz frequency spectrum about arduinofft HOT 2 OPEN

Hi,
samplingFrequency is the value which states how often per second the ADC is reading the Voltage.
sampling_period_us is just how much time is between each of those reads in microseconds or 10^-6 seconds.

In the FFT_03 example there is another value right above samplingFrequency called "samples". This value tells your ADC how many readings it should take before the Arduino performs the FFT. Because in order to calculate the FFT you need a complete array of readings.

So if you have a samplingFrequency of 100Hz this would give you a sampling_period_us value of 10 000 microseconds or 0.01 seconds. Which means every 0.01 seconds your ADC is measuring the Voltage once. This happens for samples amount of times so if you set your samples value to 64 you will end up with an array of 64 Voltage readings which would take 0.64 seconds to measure.

So to end up with 2-3seconds of sampling time you just need to adjust the samples value. Be sure it is a power of 2 (2, 4, 8, 16, ...1024 etc.). If you set it to 256 samples this would take 2.56 seconds which would be right in your desired time.

However if you want to see if the motor has some weird frequency's going on that are above 50Hz you would need to increase the samplingFrequency but i think you understood that part about Nyquist.

Hope this helps!
David

from arduinofft.