System
Product Description
HI 803 211 E Rev. 1.01.00
Page 59 of 110
4.12
Noise Blanking
This chapter describes how noise blanking of I/O modules operates in the HIQuad X system.
4.12.1
Effects of Noise Blanking
Noise blanking suppresses transient interference to increase the system availability. It ensures
that the system triggers a safety-related response to existing interferences within the configured
time.
Noise blanking can be activated for I/O modules. For details, refer to the SILworX Hardware
Editor and the module-specific manuals.
If an interference is blanked out, the system automatically processes the last valid input and
output values instead of the currently disturbed values. The time in which noise can be blanked
out is limited by the safety time, watchdog time and the cycle time.
The maximum noise blanking time can be calculated using the following equation:
Maximum noise blanking time = safety time - (2 x 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.
Minimum noise blanking time = maximum noise blanking time - cycle time
Noise blanking is effective if the cycle time value is less than the noise blanking time.
4.12.2
Configuring Noise Blanking
To blank out as many cycles as possible, the safety time must be set as large as possible taking
the process safety time 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 synchronization of an
additional processor module. Refer to the safety manual (HI 803 209 E) for further details on the
various time parameters and their application.
Configure noise blanking in accordance with the following examples:
Example
1
2
3
Safety Time [ms]
600
2000
1000
Watchdog Time [ms]
200
500
500
Target Cycle Time [ms]
100
200
200
Max. Noise Blanking Time [ms]
200
1000
0
Min. Noise Blanking Time [ms]
100
800
0
1
)
Default setting in SILworX.
2
)
No noise blanking is possible in example 3 since the noise blanking time is less than the
cycle time.
Table 21: Example for Calculating the Minimum and Maximum Noise Blanking Time
Summary of Contents for HIQuad H41X
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Page 109: ......
