Spectrum Controls 1756sc-IF8u - Manual (Page 60)

48 ControlLogix ™ Universal Analog Input Module
The module filter is a built-in feature of the Analog-to-Digital convertor
which attenuates the input signal beginning at the specified frequency. This
feature is used on a individual channel basis.
In addition to frequency rejection, a by-product of the filter selection is the
minimum sample rate (RTS) that is available. For example, the 1000Hz
selection will not attenuate any frequencies less than 1000Hz and will
allow sampling of all 8 channels within 38ms. But the 10Hz selection will
reject all frequencies above 10Hz and will only allow sampling all 8
channels within 988ms.
.ADCFilter
0-4 SINT
Analog to digital converter (ADC) filter value. The signal read by the
ADC is filtered prior to being available to the user.
0 = 50/60Hz
1 = 10Hz
2 = 100Hz
3 = 250Hz
4 = 1,000Hz.
Digital Filter
The digital filter smoothes input data noise transients on each input
channel. This value specifies the time constant for a digital first order lag
filter on the input. It is specified in units of milliseconds. A value of 0
disables the filter.
The digital filter equation is a classic first order lag equation.
Using a step input change to illustrate the filter response, as shown below,
you can see that when the digital filter time constant elapses, 63.2% of the
total response is reached. each additional time constant achieves 63.2% of
the remaining response.