Ronan XSD-1000 - Manual (Page 15)

14
Time Constant
This is the Time Constant for Background Averaging. This number is usually about 180
seconds (3 minutes). Background radiation changes are slight and slow, and a long time
constant is required to reduce the statistical noise.
It acts as a digital filter on the raw counts to establish the baseline for all detection
activities. The long time constant value filters the raw signal, yet permits the system to
constantly calibrate itself through background changes between day/night and seasons.