Filter operation (FIR and IIR), index 0x80n0:06, 0x80n0:15

Filter operation (FIR and IIR), index 0x80n0:06, 0x80n0:15

The EL 31xx terminals incorporate a digital filter which, depending on its settings, can adopt the characteristics of a Finite Impulse Response filter (an FIR filter), or an Infinite Impulse Response filter (an IIR filter). The filter is deactivated by default. Please observe the following note regarding activation with index 0x8000:06.

Activation of the filter with index 0x8000:06 and setting of the filter characteristics via index 0x8000:15 The filter frequencies are set for all channels of the EL3xxx terminals centrally via index 0x8000:15 (channel 1). The corresponding indices 0x80n0:15 of the other channels have no parameterization function.

FIR filter

Parameterized via the index 0x8000:15.

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. A 50 Hz and a 60 Hz filter are available.
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.

IIR filter

The filter with IIR characteristic is a time-discrete, linear, time-invariant low-pass filter of 1st order (-20dB/decade), which can be adjusted in 8 levels, i.e. cut-off frequencies. (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.
Through the synchronization mode FreeRun the IIR filter operates with an internal cycle time of 180 µs (1 or 2 channels) or 500 µs (4 channels).