Filter

FIR filter

The filter is a non-recursive notch filter. You can set the filter via the CoE parameter 0x8000:15. The following filter frequencies are available:

• 50 Hz
• 60 Hz

The filter determines the cycle time of the EtherCAT Box in synchronization mode "Free Run":

• 50 Hz filter: 615 µs
• 60 Hz filter: 512 µs

A notch filter has zeros (notches) in its frequency response at the filter frequency and multiples of the filter frequency. These frequencies are therefore attenuated in amplitude.

Typical attenuation curve of a notch filter with 50 Hz filter frequency

IIR filter

The filter with IIR characteristic is a time-discrete, linear, time invariant filter. It can be adjusted in 8 levels:

• IIR 1 = weak recursive filter
• …
• IIR 8 = strong recursive filter

An IIR filter can be understood to be a sliding mean value calculation after a low pass.

If the IIR filter is activated, the Box runs in synchronization mode "Free Run" with a cycle time of 500 µs.

The cycle time is independent of the number of activated measuring channels when the IIR filter is activated. You cannot shorten it by disabling channels.

Filter characteristics for IIR filters