3 Product Description HIMax System
HI 801 001 E Rev. 4.01 Page 38 of 122
The maximum noise blanking time can be determined with the following formula:
Max. noise blanking time = safety time - (2 * watchdog time)
The greater the noise blanking time value, the longer the interference can be blanked out.
Since an interference can be present for up to one cycle before it is detected while reading
in the values, the minimum noise blanking time can be determined by subtracting a cycle
from the maximum noise blanking time value.
Min. noise blanking time = Max. noise blanking time - cycle time
Noise blanking is effective if the cycle time value is less than the noise blanking time.
3.5.2 Configuring Noise Blanking
Configure noise blanking in accordance with the following examples:
Example 1
1)
2 3
2)
Safety time [ms] 600 2000 1000
Watchdog time [ms] 200 500 500
Cycle time [ms] 100 200 200
Max. noise blanking
time
[ms]
200 1000 0
Min. noise blanking
time
[ms]
100 800 0
1)
Default settings in SILworX
2)
No noise blanking is possible in example 3 since the noise blanking time is less than the
cycle time.
Table 13: Examples of Calculating the min. and max. Noise Blanking Time
Summary and Recommendations
To blank out as many cycles as possible, the safety time must be set as large as possible
taking the fault tolerance time (FTT) into account. At the same time, the value set for the
watchdog time should be as low as possible, but sufficiently large to allow reload and an
additional processor module to be synchronized. Refer to the Safety Manual (HI 801 003 E)
for further details on the various time parameters and their application.
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