What Is Digital-Input Filter (Di Filter) - ICPDAS ET-2268 CR User Manual

ET-2200 Series Ethernet I/O Modules
A.4

What is Digital-Input Filter (DI Filter)?

A: An input signal can come from a myriad of sources, such as buttons, switches, sensors, relays, etc.
Each of these types of mechanical devices also contributes to a common problem - "contact bounce".
The switch between Digital Input states is usually accompanied by several unwanted pulses, known
as "switch bounce". In certain environments and situations, these input signals may inevitably
generate an unstable signal or noise, which can potentially cause incorrect data counting or
operation failure. Consequently, these errors must be removed from the input signals, especially if
the signals are used in crucial applications.
A low-pass Digital Input filter is a software function that can be used to eliminate high-frequency
interference from input signals. The input state will only be changed when the width of any new
signal is greater than the value specified as the filtering time, meaning that short, high-frequency
interference pulses will be ignored, as illustrated in the diagram below. This is especially useful when
attempting to eliminate contact bounce.
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