Proportional Output - Xylem WTW DIQ/S 281 Operating Manual

Outputs
Monitoring limit-
ing values using
one or two relays
84
Measured
t1
value
Relay 1
UL
1
LL
Relay 2
1 Upper limit value (relay 1) exceeded
2 Selected switching delay t1 for relay 1 1 expired
Relay 1 switches
3 Hysteresis for upper limiting value (relay 1) undercut
4 Selected switching delay t1 for relay 1 1 expired
Relay 1 switches back
5 Lower limit value (relay 2) undercut
Selected switching delay t2 for relay 1 1 expired
Relay 2 switches
figure 6-1 Switching points for relays with the function of a limit indicator
A switching delay (t) can be set up for each relay for switching processes. This
is the time period for which a limiting value must be exceeded before the relay
switches. This prevents frequent switching if the measured values are close to
the limiting value.

6.2.3 Proportional output

In the case of proportional output, a relay switches cyclically on and off in a
defined measured value range (proportional range). At the same time, the relay
switches with a:
 duration of operation that corresponds to the measured value (pulse-width
output, see page 86) or
 switching frequency (frequency output, see page 86).
t1
2
4
3
5
t2
Hysteresis UL
6
Hysteresis LL
t2
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DIQ/S 281
Time
08/2020