Analog Modules
4-93
Programmable Logic Controllers S7-300 Module Data
A5E00105505-03
Scan time of the module
In the 8-channel mode of the SM 331; AI 8 x 16 bits, the channel conversion time
depends on the selected interference frequency. 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. When you set an interference frequency of
50, 60 and 400 Hz, the channel conversion time is 88 ms. The module must then
be switched over to the other channel of the group by means of opto-MOS relays.
Opto-MOS relays need 7 ms to switch and settle. Table 4-56 shows the scan times
of the module at certain interference frequencies.
Table 4-56 Scan times in 8-channel mode
Interference frequency
(Hz)
Channel scan time
(ms)
Module scan time
(All channels)
50 83 166
60 72 144
400 23 46
400/60/50 95 190
4.19.3 4-channel mode
Description of the module cycle
In 4-channel mode, the SM 331; AI 8 x 16 bits 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 4-36 4-channel mode cycle
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