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This way, an alarm will warn the user when pH goes over
the alarm thresholds, the power breaks down and in case of
a broken wire between the process meter and the external
alarm circuit .
Note
In order to have the Fail Safe feature activated, an external
power supply has to be connected to the alarm device .
CONTROL THROUGH ANALOG OUTPUT
Instead of configuring relays, it is possible
to have an output signal (selectable among
0-20 mA and 4-20 mA) proportional to the
PID action at the analog output terminals .
With this output, the actual output level amplitude is varied
continuously (with an update delay of 5 seconds) between
the maximum and the minimum values rather than varying
the proportion of ON and OFF times (duty cycle control) .
The output signal range can be selected through setup items
O .11 (output #1) and O .21 (output #2) .
A device with analog input (e .g . a pump with a 0-20 mA
input) can be connected to these terminals .
The analog output #1 is associated to setpoint 1 and the
analog output #2 to setpoint 2 .
To have a control through analog output, a setpoint has to
be configured to “PidL” or “PidH” and the corresponding
output has to be set to Control instead of Recorder: “SEt”
value in setup item O .10 (analog output #1) or O .20
(analog output #2) .
In this case no relay can be associated with the same set-
point to be used for the control, otherwise it is not possible to
set O .10 (or O .20) to “SEt” . On the other hand if a control
through analog output is already associated with a setpoint,
it is not possible to configure a relay to the same setpoint .
