Commissioning Liquisys M CPM223/253
56 Endress+Hauser
SCS operating voltage for pH sensors with Memosens functionality
If the connection between the pH sensor with Memosens functionality and cable is just
connected but not locked, the supply voltage can drop below the required voltage value due
to the poor coupling. This results in incorrect measurement.
With the SCS operating voltage, the supply voltage of a pH sensors with Memosens
functionality is monitored.
If this value drops below the safety limit, the measured value is ignored and the error E 127
is output.
6.6.6 Relay contact configuration
To use the RELAY function group you need a relay board which is not part of the basic
version.
The following relay contacts can be selected and configured as desired (max. four contacts,
depending on options installed):
• Limit contactor for pH / ORP: R2 (1)
• Limit contactor for temperature: R2 (2)
•PID controller: R2 (3)
• Timer for cleaning function: R2 (4)
• Chemoclean function: R2 (5)
• Neutralization controller: R2 (6) (for Plus Package)
Limit contactor for measured pH / ORP and temperature
The transmitter has different ways of assigning a relay contact.
Switch-on and switch-off points and pick-up and drop-out delays can be assigned to the limit
contactor. In addition, you can configure an alarm threshold to output an error message and
to start a cleaning function in conjunction with this.
These functions can be used both for pH/ORP measurement and for temperature
measurement.
Please refer to å 38 for a clear illustration of the relay contact states.
• When the measured values increase (maximum function), the relay contact is closed as of
t
2
after the switch-on point (t
1
) has been overshot and the pick-up delay has elapsed
(t
2
-t
1
).
The alarm contact switches if the alarm threshold (t
3
) is reached and the alarm delay
(t
4
-t
3
) has also elapsed.
• When the measured values decrease, the alarm contact is reset when the alarm threshold
(t
5
) is undershot as is the relay contact (t
7
) after the drop-out delay (t
7
-t
6
).
• If the pick-up and drop-out delays are set to 0 s, the switch-on and switch-off points are
also switch points of the contacts.
Settings can also be made for a minimum function in the same way as for a maximum
function.
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