FIR and IIR filters (0x382199, 0x302199)

Enable filter

The digital filter is enabled in the factory setting index 0x80A0:06 "Enable filter" = TRUE

To disable the filter, set index 0x80A0:06 "Enable filter" = FALSE

Notice

Measured value jumps when enabling or disabling filters

When filters are enabled or disabled, short-term measured value jumps can occur in the process data that do not correspond to the physical values.

Select filter type

You can select the filter type via index 0x80A0:15 "Filter settings".

Filter type	Values in 0x80A0:15 "Filter settings"
FIR filter: Filter with Finite Impulse Response	0: "50 Hz FIR" (factory setting) 1: "60 Hz FIR"
IIR filter: Filter with Infinite Impulse Response	2: "IIR 1" 3: "IIR 2" 4: "IIR 3" 5: "IIR 4" 6: "IIR 5" 7: "IIR 6" 8: "IIR 7" 9: "IIR 8"

Conversion time and filter

The conversion time is the interval during which the terminal provides a new measured value.

The typ. conversion time and trigger mode depend on

the selected filter setting (default: 50 Hz)
the setting of the synchronization mode in CoE register 0x1C33:01

by manually parameterizing in the System Manager.
Notice Enter the changes made in the StartUp list!
by the StartUp list as an automatic parameter download during the EtherCAT start phase.
Notice Entries are implemented only after activation of the configuration!

FIR filter (Finite Impulse Response)

The filter performs a notch filter function and determines the conversion time of the terminal. The higher the filter frequency, the faster the conversion time.
Notch filter means that the filter has zeros (notches) in the frequency response at the filter frequency and multiples thereof, i.e. it attenuates the amplitude at these frequencies.

The FIR filter operates as a non-recursive filter.

FIR and IIR filters (0x382199, 0x302199) 1: — typical attenuation curve of notch filter at 50 Hz

Filter data for FIR filter (1 to 4-channel terminals)

FIR filter	Attenuation	Cut-off frequency (-3 dB)
50 Hz FIR	> 60 dB	31 Hz
60 Hz FIR	> 50 dB	37 Hz

IIR filter (Infinite Impulse Response)

The filter with IIR characteristics is a time-discrete, linear, time invariant filter that can be set to 8 levels (level 1 = weak recursive filter, up to level 8 = strong recursive filter).

The IIR can be understood to be a moving average value calculation after a low-pass filter.

Thanks to the FreeRun synchronization mode, the IIR filter operates with an internal cycle time of 500 µs.

IIR filter	Cut-off frequency with terminal-internal cycle time 500 µs (-3 dB)
IIR 1	260 Hz
IIR 2	180 Hz
IIR 3	85 Hz
IIR 4	45 Hz
IIR 5	22 Hz
IIR 6	11 Hz
IIR 7	5.2 Hz
IIR 8	2.6 Hz