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the_jackal
Joined: 15 Dec 2004
Posts: 82
Helped: 3
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 17 Dec 2004 11:12 Analog signal < 10kHz |
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| An analog signal contains frequencies up to 10kHz. What range of sampling frequencies allows exact reconstruction of this signal from its sample?
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arturt134
Joined: 01 Jan 1970
Posts: 140
Helped: 1
Location: Poland
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| 17 Dec 2004 13:55 Re: Analog signal < 10kHz |
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There is Nyquist law: sampling frequency should be twice signal frequency to exact rebuild sampled signal.
Practically, for better performance, for signal 10kHz use sampling frequency bigger than 20kHz, maybe 25-30kHz.
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picus
Joined: 05 May 2004
Posts: 39
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| 17 Dec 2004 14:19 Re: Analog signal < 10kHz |
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Ok for Nyquist but you can use a prefilter first.
i.e.
-------------------- ----------------
---- | low pass filter | ---- > --- | ADC conv. | ---->----
-------------------- ----------------
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Circuit_seller
Joined: 23 Sep 2002
Posts: 414
Helped: 15
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| 18 Dec 2004 6:14 Re: Analog signal < 10kHz |
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Hi
It is completly depends on your dynamic range and antialiasing filter sharpness. more dynamic range( number of ADC bit) requires either shaper antialaising filter or more sampling rate.
Regards
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v_naren
Guest
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| 21 Dec 2004 6:24 Re: Analog signal < 10kHz |
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| the ideal sampling freqyency will be 20KHz if there is an ideal low pass filter
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IanP
Joined: 05 Oct 2004
Posts: 6346
Helped: 1505
Location: West Coast
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| 21 Dec 2004 6:40 Re: Analog signal < 10kHz |
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Exact reconstruction will occure if you have infinite number of samples.
This business with Nyquist criterion only gives us the minimum frequency (2 x Max frequency in original) at which you will be able to "follow" the original.
In practice, if you want the reconstraction to be of good quality take as many samples as you can .. obviously be reasonable and don't exaggerate.
I think in your case of 10kHz something close to 100ks/s will give you quite good copy.
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machael
Joined: 04 Nov 2004
Posts: 46
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| 21 Dec 2004 7:06 Analog signal < 10kHz |
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Theoretically, 20kHz is enough.
However, in practical , you 'd better use a sample rate above 20kHz. 30~40kHz is enough.
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Circuit_seller
Joined: 23 Sep 2002
Posts: 414
Helped: 15
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| 21 Dec 2004 7:13 Re: Analog signal < 10kHz |
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Hi
I think the sampling rate depends on the "tolerable aliasing", "tolerable distortion" and dynamic range of the ADC.
We can not advise him/her to take a sampling frequency and we do not know the specifications.
Regards
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