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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