Siemens SIMATIC PCS 7 Operating Manual page 158

Configuring the safety program
7.11 Monitoring times and system response times
F signal module
EM 4 F-DO Ex 17.4V/40mA
6ES7138-7FD00-0AB0
EM 4 F-AI Ex HART
6ES7138-7FA00-0AB0
The discrepancy time is not contained in T
T
DIS
158
T
WCDT
Example calculation of the response time of EM 8 F-DI Ex NAMUR:
Parameter assignment:
•
– 1oo2 (2v2) evaluation (equivalent or non-equivalent)
– Discrepancy behavior: Provide last valid value
– Discrepancy time: 400 ms
– Sensor supply at 1oo2 (2v2): Sensor n and n+4 to Vs n
– Input delay: 3 ms
– Sensor supply test: Activated
– Time for sensor test: 10 ms
– Start-up time of the sensor after sensor test: 100 ms
Response time = Internal processing time + input delay + discrepancy time + (time for
•
sensor testCHANNEL(n) + start-up time of the sensor after sensor testCHANNEL(n)) +
(time for sensor testCHANNEL(n+4) + start-up time of the sensor after sensor
testCHANNEL(n+4))
Result: Response time = 48 ms + 3 ms + 400 ms + (10 ms +100 ms ) + (0) = 561 ms
Response time = Internal processing time + input delay + discrepancy time + 2 x { (time
•
for sensor testCHANNEL(n) + start-up time of the sensor after sensor testCHANNEL(n))
+ (time for sensor testCHANNEL(n+4) + start-up time of the sensor after sensor
testCHANNEL(n+4)) }
Result: Response time = 48 ms + 3 ms + 400 ms + 2x{(10 ms +100 ms ) + (0) } = 671
ms
Cycle time = 7 ms + configured light test time
Response time = 9 ms + max. {configured light test time; configured max. dark test read-
•
back time}
Example:
Parameter assignment:
•
– Light test time: 3 ms
– Max. dark test readback time: 10 ms
Cycle time: 7 ms + 3 ms = 10 ms
•
Response time: 9 ms + max. {3, 10} = 9 ms + 10 ms = 19 ms
•
Typical response time (when no errors present)
= conversion cycle time × filter
Maximum response time (when no errors pre-
sent) = 2 × conversion cycle time × filter
Example:
Interference frequency 50 Hz, filter = 1
•
conversion cycle time, 4 active channels
Maximum response time (when no errors
•
present) = 2 × 109 ms × 1 = 218 ms
.
T
OFDT
Maximum response time (with channel
error) = 2 x conversion cycle time
Example:
Interference frequency 50 Hz, 4 active
•
channels
Maximum response time (with channel
•
error) = 2 x 109 ms = 218 ms
. It should always be entered at parameter
OFDT
Compendium Part B - Process Safety (V8.2)
Operating Manual, 07/2016, A5E35031794-AB