5.5
Relay contact configuration
The relay contacts described below can be
selected and configured as required (up to
four with four contacts depending on options
installed).
• Limit contactor for measured conductivity
value: R2 (1)
• Limit contactor for temperature: R2 (2)
• P(ID) controller: R2 (3)
• Timer for cleaning function: R2 (4)
• Chemoclean function: R2 (5)
• USP 23: R2 (6) (S version, conductive only)
5.5.1
Limit contactor for measured conductivity value and temperature
The relay contacts in the Liquisys M can be
assigned different functions.
Switch-on and switch-off points and pickup
and dropout delays can be defined for the
limit contactor. Moreover, an alarm threshold
can be set to issue an error message and to
start a cleaning function.
These functions may be used for conductivity
and temperature measurement.
Please refer to Fig. 5.5 for a graphic
representation of the contact states of any
relay or alarm contact.
When the measured value increases (max
function), the relay contact is closed at time t
2
when the switch-on point has been exceeded
(t
1
) and the pickup delay (t
2
– t
1
) has expired.
When the alarm threshold (t
3
) is reached and
the alarm delay (t
4
– t
3
) also has expired, the
alarm contact is switched.
When the measured value decreases, the
alarm contact is reopened when the
measured value drops below the alarm
threshold (t
5
), and the relay contact also
opens (t
7
, after the dropout delay t
7
– t
6
).
When the pickup and dropout delays are set
to 0 s, the switch-on and switch-off points are
identical to the contact switching points.
Settings analogous to the max function can
also be made for a min function.
5.5.2
P(ID) controller
The Liquisys M supports the definition of
various controller functions. On the basis of
the PID controller, P, PI, PD and PID
controllers can be implemented. The
best control response is obtained using the
controller best suited to the application in
question:
GRENZ.CDR
Meas. value
Switch-on point
Switch-off point
Alarm threshold
t
1
t
2
t
4
t
3
t
5
t
7
t
t
6
Switch-on point > switch-off point: maximum function
Switch-on point < switch-off point: minimum function
Switch-on point
Switch-off point
t
1
t
2
t
6
t
7
t
Contact ON
Contact OFF
Contact ON
Contact OFF
Alarm ON
Alarm OFF
Fig. 5.5
Relationships between
switch-on and switch-off
points and pickup and
dropout delays
LM253E5B.CHP
Liquisys M CLM 223 / 253
Instrument configuration
Hauser
31
