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Note
Connecting an external device (e.g. chart recorder) to the controller, the procedure is
easier and doesn’t need the use of hand plotting the process variable (EC or TDS).
ALARM RELAY
The alarm relay functions in the following manner:
During alarm condition, the relay is de-energized. When not in alarm condition, the
relay is energized.
Example: High alarm set at 1400 µS
Low alarm set at 600 µS
An hysteresis will eliminate the possibility of continuous sequences
‘energizing/de-energizing’ of the alarm relay when the measured value is close to the
alarm setpoint. The alarm hysteresis amplitude is 1.5% of full scale.
Moreover the alarm signal is generated only after a user selectable time period
(alarm mask) has elapsed since the controlled value has overtaken one alarm threshold.
This additional feature will avoid fake or temporary alarm conditions.
Note
If the power supply is interrupted, the relay is de-energized as if in alarm condition to
alert the operator.
In addition to the user-selectable alarm relays, all EC/TDS controllers are equipped with
the
Fail Safe
alarm feature.
FS•O = NC (Normally Closed)
De-energized Relay
COM
FS•C = NO (Normally Open)
Energized Relay
