F 6217 (0606)
295
Interferences of the module in low frequency range (10 Hz)
External disturbing pulses in the range of 10 Hz, e.g. at pressure measurements of nearby pis-
ton pumps, can lead to temporary channel bit faults at the analog inputs. Internal hardware
tests carried out in the same rhythm are influenced by this pulses (fluctuations) in an adverse
way. Input channels could be interpreted as faulty and de-energized.
Solution
– Pressure sensors:
By internal damping via adjustable digital filters in the sensor disturbing pulses can be min-
imized or eliminated.
– Use of low-pass filter H 7017:
The high time constant of the low-pass filter eliminates the low frequency disturbing pulses
in the input current.
The low-pass filter may only be used in safety-related circuits with low-
shut-down because in case of a failure in the filter (leakage current) the
measured values are reduced. The time relay of the filter has to be
regarded in calculating the safety time.
Note Additional transmitter supplies, e.g. via front cable plug Z 7128, have
no disturbing influences on the operation of the module F 6217.
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