# Filtering

Filtering is one of the most commonly used signal processing techniques. Signal conditioning systems can filter unwanted signals or noise from the signal you are measuring. Use a noise filter on low-rate, or slowly changing, signals, such as temperature, to eliminate higher frequency signals that can reduce signal accuracy. A common use of a filter is to eliminate the noise from a 50 or 60 Hz AC power line. A lowpass filter of 4 Hz removes the 50 or 60 Hz AC noise from signals sampled at low rates. A lowpass filter eliminates all signal frequency components above the cutoff frequency. Many signal conditioning modules have lowpass filters that have software-selectable cutoff frequencies from 10 Hz to 25 kHz.