Section 4
Binary input and output modules
4.1
Binary input
4.1.1
Binary input debounce filter
The debounce filter eliminates bounces and short disturbances on a binary input.
A time counter is used for filtering. The time counter is increased once in a millisecond
when a binary input is high, or decreased when a binary input is low. A new debounced
binary input signal is forwarded when the time counter reaches the set
DebounceTime
value and the debounced input value is high or when the time counter reaches 0 and the
debounced input value is low. The default setting of
DebounceTime
is 5 ms.
The binary input ON-event gets the time stamp of the first rising edge, after which the
counter does not reach 0 again. The same happens when the signal goes down to 0 again.
Each binary input has a filter time parameter
DebounceTimex
, where x is the number of
the binary input of the module in question (for example
DebounceTime1
).
The debounce time should be set to the same value for all channels on the
board.
4.1.2
Oscillation filter
Binary input wiring can be very long in substations and there are electromagnetic fields
from for example nearby breakers. Floating input lines can result in disturbances to binary
inputs. These disturbances are unwanted in the system. An oscillation filter is used to
reduce the disturbance from the system when a binary input starts oscillating.
Each debounced input signal change increments of an oscillation counter. Every time the
oscillation time counter reaches the set
OscillationTime
, the oscillation counter is checked
and both the time counter and the oscillation counter are reset. If the counter value is above
the set
OscillationCount
value the signal is declared as oscillating and not valid. If the
value is below the set
OscillationCount
value, the signal is declared as valid again. During
counting of the oscillation time the status of the signal remains unchanged, leading to a
fixed delay in the status update, even if the signal has attained normal status again.
1MRK 502 048-UUS A
Section 4
Binary input and output modules
57
Technical manual
