Signal Filtering
Original instructions
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Description
A programmable debounce filter with 4 levels (Without, Low, Medium, and High) is available at every input. Filtering the input signal discards from glitches superimposed on the pickup signal.
The filter can limit the frequency within the application range, and remove higher frequencies before filtering.
Selecting the Filtering Level
The following table specifies the effect of the selected level of filtering:
Filtering level
Effect on the input signal
Without(1)
Pulse detected: 1 μs
Frequency detected: 500 kHz
Low(2)
Pulse rejected: Less than 4 μs
Frequency cut: 100 kHz
Medium
Pulse rejected: Less than 40 μs
Frequency cut: 10 kHz
High
Pulse rejected: Less than 400 μs
Frequency cut: 1 kHz
(1) When the Input Sensor filter parameter is set to Without, the pulse rejection is not specified and the frequency cut is above 500 kHz. This option may be used for incremental encoders only. (2) Default value for Input Sensor filter parameter in Control Expert configuration screen.
NOTE: Frequencies are given for square wave signal.
Debounce Filter Diagrams
The figure below shows an example of MPU signal, filtered in Low mode: 
1
Noisy MPU signal 
2
Threshold 
3
Input signal 
4
Signal filtered
In Low mode, the system delays all transitions until the signal is stable for 4 μs.
The figure below shows an example of APU signal, filtered in Low mode: 
1
Noisy APU signal 
2
Input signal 
3
Signal filtered
In Low mode, the system delays all transitions until the signal is stable for 4 μs.