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Need Tips About How to Make a Good Acquisition System

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Member level 4
Feb 23, 2002
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Hi to all,
I know the basis of system acquisition, An OA -> ADC -> UC -> Display.
But now i am in charge to desing a system with 16 analog input, with a
1KSample/channel, and i read that this kind of system need a window filter before the Mux to eliminate the aliasing and another after it to eliminate the noise introducted by it. And i couldn´t found how to calculate this kind of filters and how to select the right adc and mux for this proyect. If anyone know were i can find an ebook or web were i can learn about it, i will apreciate very much.

thxs for you time

two factors on the filter

There are two factors that affect the input filter. The first is the pass band and stop band frequency. To prevent aliasing, the filter should attenuate all signals higher than half the sampling frequency. Since a perfect drop is not possible, you will end up with a pass band of about a third of the sampling frequency. This all assumes that the noise is much broader band than the signals. If the noise power integrated over several times the sampling rate is still lower than 1 LSB of your system and the signal power is confined by its own characteristics to below half of the sampling rate, you can use a much wider filter.
The second factor is the amplitude ripple which will affect the measurement accuracy. I suggest selecting a ripple of less than half of your amplitude measurement error budget. Filter design programs such as the 20 day free one from **broken link removed** will design such filters.


... and also, you need to be careful with the AO output impedance wish must be adequated with de ADC input impedance.

Best Regards

Thanks flatulent and pendragon, i will use it in me design.

/ Warning #2 - No thanks at Elektroda! /

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