REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-357
· Where only the measurement part of the function is in use,
the binary impulse and reset inputs of both impulse counters
must be disabled, i.e. “always FALSE”.
3.7.5.1. Impulse counter inputs
The impulses counted are normally generated by a measuring or
metering device (see Fig. 3.7.5.1).
t
Pulse
Pulse
Pulse
f
1
T =
t
Pause
Fig. 3.7.5.1 Impulse counter input signal
The maximum impulse repetition rate is 25 Hz (see Fig. 3.7.5.1).
Thus the minimum time between the positive-going edges of two
input impulses is
ms40Hz
25
1
T
min,Puls
== .
The pulse-width is determined by the function generating the
impulses and the ratio between the pulse-width and the interval
between lagging and leading edges should be in the range 1:3 to
1:1, i.e.:
ms10T
4
1
T
31
1
t
min,Pulsemin,Pulsemin,Pulse
=´=´
+
= .
Since the impulse counter is polled approximately every 5 ms,
impulses are reliably detected with a safety factor of about 2.
The impulse counter evaluates the positive-going edges (0
à1)
of the input signal.
To filter any contact bounce (debouncing) phenomena, only the
first positive-going edge is evaluated within a given period
(typically 10 ms).
To Next Page
Loading...
