Publication 1734-UM001D-EN-P - April 2008
POINT I/O Module Data 109
Digital Filter
A digital filter is available on the input modules. You set a time constant that is
used in the equation:
Yn = Yn-1 + (dt / (dt + T
A
) * (Xn-Yn-1)
Where: Yn = new data
Yn-1 = old data.
dt = Channel Update Rate in milliseconds
T
A
= digital filter time constant
Xn = present unfiltered data
T
A
can be an integer from 0 to 10,000 ms. If set to 0, the filter is disabled
The default setting is disabled. This is done by setting the time constant (TA)
to zero. Each channel can be configured individually for time constant but
update rate (dt) is done on a per module basis.
Update Rate
The update rate determines how often a channel is scanned. The maximum
rate is determined by the notch filter setting. The minimum update rate is
10,000 ms.
• 120 ms maximum update rate - 50 Hz
• 100 ms update rate - 60 Hz
• 24 ms update rate - 250 Hz
• 12 ms update rate - 500 Hz
Notch Filter
Select a notch filter. The notch filter is for both inputs. Valid settings are the
following:
• 50 Hz - 120 ms maximum update rate
• 60 Hz - 100 ms update rate
• 250 Hz - 24 ms update rate
• 500 Hz - 12 ms update rate
The update rate determines the rate at which the inputs are sampled.
Maximum update rate is determined by the notch filter setting. The notch filter
parameter is used to select the fastest possible rate. Minimum update rate is
10,000 ms.
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