Analog Modules
4-148
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
Scan time of the module
In the 8-channel software filter mode of analog input module SM331; AI 8 x TC, the
channel conversion time is guided by the interference frequency set. When you set
an interference frequency of 50 Hz, the channel conversion time including
communication time is 76 ms. When you set an interference frequency of 60 Hz,
the channel conversion time is 65 ms. When you set an interference frequency of
400 Hz, the channel conversion time is reduced to 16 ms. As with 8-channel
hardware filter mode, the module must be switched over by means of opto MOS
relays with a switchover time of 7 ms to the other channel of the group. Table 4-75
shows the scan time of the module at a certain interference frequency.
Table 4-75 Scan Times in “Software Filter, 8 Channels” Mode
Programmed
Interference Frequency
Suppression
Channel Scan Time* Module Scan Time (All
Channels)
50 Hz 83 ms 166 ms
60 Hz 72 ms 144 ms
400 Hz 23 ms 46 ms
* Channel scan time = channel conversion time + 7 ms switching time to the other channel
in the channel group
“Hardware filter 4 channels” mode
In 4-channel hardware filter mode, the analog input module SM331; AI 8 x TC does
not switch over between the channels of the individual groups. As the module
contains four analog/digital converters (ADC), all four of the ADCs convert
simultaneously for channels 0, 2, 4 and 6.
Scan time
Start analog conversion
(simultaneous)
K0 K2 K4 K6
Figure 4-48 Hardware filter 4 channels scan time
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