Data Acquisition Systems
A Selection Guide: Filters, Sampling and Throughput
The Neff Selector
- a step-by-step tutorial designed to help you find the Neff product
that fits your data acquisition needs.
Filtering, Sampling and Throughput
Filters are used to remove unwanted variations or
noise from the signal to be measured. The cutoff frequency selected
must allow the desired signal to pass while attenuating unwanted
signals to a level that can be tolerated; usually the resolution
of the ADC. Filters with no attenuation in the passband and infinite
attenuation at all frequencies above it with no transition band
are not achievable, especially when using analog filters. The ideal
is more approachable when using digital filters. Low-pass filters
are generally used in data acquisition.
There is no hard and fast rule defining sampling
rate. One can calculate a minimum sampling rate required to avoid
aliasing depending upon filter cutoff frequency, see Application
Note 504; a rate can be chosen that will provide sufficient
data to reproduce the input signal or to determine the peak values
within specified limits.
The overall throughput capabilities of the system
must, of course, support the quantity of channels required at the
sampling rate needed.
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