Signal Processing - Sampling rate basics

• Q: does an 8 kHz sampling rate mean 8 samples per second? What is sampling rate?
  • 8 kHz = 8,000 samples per second, one every 0.125 ms
  • like a camera’s frame rate; resolution (bits) is the megapixels: the RA2A2 is 24-bit but only 8 kHz
• the highest frequency you can see is half the sampling rate
  • faster content aliases: at 8 kHz the samples show slower, fake wiggles instead of the arc noise
  • at 50 kHz they are close enough to trace most of it
  • choosing hardware: find the band the arc features need, then sample at least 2×, in practice a few times higher
• 50 Hz mains: one cycle is 20 ms, so 8,000 ÷ 50 = 160 samples per cycle
  • arc algorithms look at one cycle (or half-cycle) at a time
  • model input: raw samples (160, 1) per cycle into a 1D-CNN, or features per cycle (peak, RMS, difference from the previous cycle)
• cycle = one repetition; period = its time (20 ms); frequency = cycles per second (50 Hz) = 1 / period