Siemens S7-300 - Page 325

Response times
D.1 Response Times
Fail-safe signal modules
Installation and Operating Manual, 01/2010, A5E00085586-10
325
Response time of SM 336; F-AI 6 x 0/4 ... 20 mA HART
● Calculation of the response time (conversion time) of SM 336; F-AI 6 x 0/4 ... 20 mA
HART with and without active fault according to the following formula:
Typical response time (without active fault) = Conversion cycle time × Smoothing
Typical response time (without active fault) = 2 × Conversion cycle time × Smoothing
Example
Fault frequency 50 Hz, Smoothing = 1 conversion cycle, 3 active channel pairs:
Max. response time (without active fault) = 2 × 125 ms × 1 = 250 ms
● If a discrepancy occurred during 1oo2 evaluation, the maximum response time is
calculated according to the following formula:
Maximum response time (in case of discrepancy) = 2 × Conversion cycle time ×
Smoothing + Discrepancy time + 2 × Conversion cycle time
The discrepancy time is the configured discrepancy time.
Example
Fault frequency 50 Hz, Smoothing = 1 conversion cycle, discrepancy time = 2000 ms, 3
active channel pairs:
Maximum response time (in case of discrepancy) = 2 × 125 ms × 1 + 2000 ms + 2 × 125
ms = 2500 ms
● If a channel fault occurred, the maximum response time is calculated according to the
following formula:
Maximum response time (in case of a channel fault) = 2 × Conversion cycle time
Example
Fault frequency 50 Hz, 3 active channel pairs:
Maximum response time (in case of a channel fault) = 2 × 125 ms = 250 ms
Note
You calculate the response time by using the values from Chapter "Technical Data - SM
336; F-AI 6 x 0/4 ... 20 mA HART (Page 263)" in the formulas in
dicated above.
Note on the calculation of response times
Note
Note that the Excel files for the calculation of maximum response times (s7fcotia.xls
(http://support.automation.siemens.
com/WW/view/en/11669702/133100
) and s7ftimea.xls
(http://support.automation.siemens.com/WW/view/en/26091594/133100
)) included in the S7
Distributed Safety
and S7 F/FH Systems options packages already support the calculation of
an extended "maximum response time with active error" by the amount of the assigned
discrepancy time.