Siemens Simatic S7-400 - Manual (Page 251)

Analog Modules
5-35
S7-400, M7-400 Programmable Controllers Module Specifications
A5E00069467-07
5.6 Conversion, Cycle, Setting and Response Time of
Analog Modules
Conversion Time of Analog Input Channels
The conversion time consists of a basic conversion time and additional processing
times of the module for:
• Resistance test
• Wire-break monitoring
The basic conversion time depends directly on the conversion method of the
analog input channel (integrating method, instantaneous value conversion).
In the case of integrating conversion methods, the integration time has a direct
influence on the conversion time. The integration time depends on the interference
frequency suppression that you set in STEP 7 (refer to Section 4.3.1).
To find out the basic conversion times and additional processing times of the
different analog modules, refer to the technical specifications of the module
concerned, starting at Section 5.18.
Scan Time of Analog Input Channels
Analog-to-digital conversion and the transfer of the digitized measured values to
the memory and/or to the bus backplane are performed sequentially – in other
words, the analog input channels are converted one after the other. The scan time
– in other words, the time elapsing until an analog input value is again converted, is
the sum of the conversion times of all activated analog input channels of the analog
input module.
The following figure illustrates the components of the scan time for an n-channel
analog module.
Conversion time,
channel 1
Conversion time,
channel 2
Conversion time,
channel n
Cycle time
Figure 5-4 Scan Time of an Analog Input or Output Module