| ??? 07/31/10 15:54 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#177550 - Aliasing Responding to: ???'s previous message |
Justin Fontes said:
Sonia Sanghvi said:
Maximum frequency is around 400Hz. So my sampling frequency should ideally be around 1Khz ( following the Nyquist criterion). That really depends on how stable you want the amplitude peak to become. Following the Nyquist criteria is the absolute minimum for detection, but will not give an accurate view of the amplitude always. Usually in practice, to get a good idea of the peak amplitudes of the waveform a sampling frequency will be about 8x as much as the original frequency. This also goes in line with digital scopes. A 100MHz digital scope normally samples at 1GHz. This allows them to capture the basic shape of the 100MHz sine wave - sampling at 200MHz they could manage to do all samples at the zero-crossings, and measure a zero amplitude. And if they sample slightly faster than 200MHz, they would capture something that looked like a low-frequency sine wave instead of the actuall 100MHz input signal because of the aliasing between the sampling rate and input signal. |
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| EMG | 01/01/70 00:00 | |
| Correct | 01/01/70 00:00 | |
| perhaps a little more detail would help | 01/01/70 00:00 | |
| ARM is a good place to start. | 01/01/70 00:00 | |
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| 0-10mV | 01/01/70 00:00 | |
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| Following Nyquist is the bare minimum | 01/01/70 00:00 | |
| Aliasing | 01/01/70 00:00 | |
Think about this some more ... | 01/01/70 00:00 |