I need to read a 40.1khz signal. I know there is a rule of 2. So that means an A/D of 80khz. But I need to do this real time. Can anybody make a suggestion. A single analog chanel that can read at 80khz or higher.
Also price is a consideration. Any suggestions would be helpful.
Thank you.
snipped-for-privacy@gmail.com wrote in news:1131664296.877968.224320 @g47g2000cwa.googlegroups.com:
80.2k is a mathematically ideal number. If your bandwidth really goes to 40.1k, you should be acquiring at about 95k or higher."Scott Seidman" schreef in bericht news:Xns970B5B741793Bscottseidmanmindspri@130.133.1.4...
The number two is the minium you should use. Better is an higher number. If you have an Sinus of 40.1k exactly and sample with 80.2k exactly, and the first sample is in the zero crossing, allt he samples will be 0 and you have a DC signal after the conversion. Of course this "never" happens. But any samplerate under the 80.2 will have a this problem with some frequencies.
Alexander
There is another reason why the sampling rate should be higher. Any frequencies above 40.1kHz with be aliased down. You should try and filter anything above nyquest or half sampling rate otherwise it will introduce noise into the system. IIRC telephone lines have a bandwidth of 3.3kHz and have a sampling rate of 8kHz. They use multipole filters to reduce frequency components above inquest.
"Fred" schreef in bericht news:43786478$0$23282$ snipped-for-privacy@news.zen.co.uk...
ThanX for the Addition.
I forgot to mention it.
FWIW - Phones operate on 3.2KHz. Sampled at 2.5 x 8 bits yields the commonly known voice bit rate of 64 Kbps. If you steal one bit in eight for other purposes, you get another commonly known rate, 56 Kbps. The 2.5 is higher than the 2x Nyquist reuires to account for rolloff of non-ideal filters.
Have something to add? Share your thoughts — no account required.
Ask the community — no account required