wtw TresCon UNO A111, Operating Manual

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Operation TresCon UNO
5 - 36 ba43134e08 05/2017
5.3.3 Limit indicator: Basic information
With a limit indicator, a relay switches when a specified limiting value is
exceeded or undercut.
Limit indicators can be used in the following way:

Monitoring a limiting value using a relay:
when a limiting value (upper or lower limiting value) is exceeded or
undercut, a relay switches. The
Open or Close relay actions are pos-
sible.

Monitoring two limiting values using two relays:
If the upper limiting value is exceeded or undercut, a relay switches,
and if the lower limiting value is exceeded or undercut, another relay
switches. The
Open or Close relay actions are possible.
Note
If the simple monitoring function ( Open , Close ) with one or two relays
is not sufficient, use proportional regulation (see section 5.3.1).
Monitoring limiting
values using one or two
relays
Fig. 5-15 Switching points for relays with the function of a limit indicator
1 Upper limit value (relay 1) exceeded
2 Selected switching delay t1 for relay 1 expired
Relay 1 switches
3 Hysteresis for upper limiting value (relay 1) undercut
4 Selected switching delay td1 for relay 1 expired
Relay 1 switches back
Time
Measured
value
UL
LL
Hysteresis UL
Hysteresis LL
3
6
5
Relay 1
Relay 2
4
1
2
td2
td1
td1