Analog modules
6.9 Analog input module SM 331; AI 8 x RTD; (6ES7331-7PF01-0AB0)
S7-300 Automation System Module data
6-84 Manual, 08/2006, A5E00105505-04
Cycle time of module in 8-channel mode (software filter)
However, the channel conversion time is oriented on the programmed noise suppression. At
a set interference frequency of 50 Hz, the channel conversion time is 32 ms, including
communication time. At a set an interference frequency of 60 Hz, the channel conversion
time is 27 ms. You can reduce channel conversion times to 9 ms by setting an interference
frequency of 400 Hz. As in "hardware filter, 8channel" mode, the module has to toggle to the
second channel of the group within a changeover time of 16 ms using the Opto-MOS relays.
The table below shows this relationship.
Table 6-26 Cycle times in "8-channel mode (software filter)"
Interference frequency Channel cycle time* Module cycle time (all channels)
50 Hz 48 ms 96 ms
60 Hz 43 ms 86 ms
400 Hz 25 ms 50 ms
* Channel cycle time = channel conversion time + 12 ms channel changeover time within the group
4-channel mode (hardware filter)
In this mode, the module does not toggle between the channels of the various groups. The
four ADCs of the module simultaneously convert channels 0, 2, 4 and 6.
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Figure 6-25 4-channel mode cycle time (hardware filter)
Cycle time of module in 4-channel mode (hardware filter)
In 4-channel mode, the converted value tunes to 100% within 80 ms and is updated every 10
ms. The channel and module cycle time are always identical, because the module does
toggle between the channels of a group: 10 ms.
Channel conversion time = channel cycle time = module cycle time = 10 ms
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