Reaction Time - Siemens SIMATIC S7-400H System Manual

16.5

Reaction time

Definition of reaction time
The reaction time represents the time expiring between the detection of an input signal and
the modification of its logically linked output signal.
Fluctuation length
The actual reaction time lies between the shortest and longest reaction time. Always expect
the longest reaction time when you configure your system.
The section below deals with the shortest and longest reaction times, in order to provide an
overview of the fluctuation in the length of reaction times.
Factors
The reaction time is determined by the cycle time and the following factors:
● Delay at the inputs and outputs
● Additional DP cycle times on the PROFIBUS DP network
● Processing in the user program
Delay of the I/Os
Make allowances for the following module-specific delay times:
● For digital inputs: the input delay time
● For digital inputs with interrupt function: the input delay time + internal preparation time
● For digital outputs: negligible delay times
● For relay outputs: typical delay times of 10 ms to 20 ms.
● For analog inputs: cycle time for analog input
● For analog outputs: response time at analog outputs
For information on delay times, refer to the technical specifications of the signal modules.
S7-400H
System Manual, 09/2007, A5E00267695-03
The delay of relay outputs also depends on the temperature and voltage.
S7-400 cycle and reaction times
16.5 Reaction time
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