In-Line Cleaning - Hanna Instruments HI 504 Instruction Manual

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) propor-
tional 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 (ana-
log output #2).
In this case no relay can be associated with the same setpoint
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.
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IN-LINE CLEANING

The cleaning feature allows an automatic cleaning action of
the electrodes. To perform cleaning, the controller activates
an external device (pump).
Cleaning can be of two types:
• Simple cleaning: with water only, it can be triggered only
by a timer (periodical cleaning) or by an error for which a
cleaning action can be configured (i.e. a "Reference elec-
trode broken or dirty" error).
• Advanced cleaning (optional): with water and detergent,
it can be triggered by the following events:
• timer (setup item L.15 set to "ti");
• digital input or RS485 command (external trigger; setup
item L.15 set to "E");
• timer and digital input or RS485 command (external trig-
ger; setup item L.15 set to "ti E");
• timer masked by external digital input (an external digital
input disables the cleaning; setup item L.15 set to "tiEM");
• error for which a cleaning action is configured (i.e. a
"Reference electrode broken or dirty" error).
The type of cleaning action is selected through the relays
configuration and the time between two consequent cleaning
(if timer configured) has to be set through setup item L.01 for
simple cleaning and L.13 for advanced cleaning.
Cleaning actions do never take place if no relay is config-
ured for cleaning. The advanced cleaning requires both relays
3 and 4 configured for that kind of cleaning: relay 3 is asso-
ciated with water and relay 4 corresponds to detergent.
A minimum pause time has to be set for advanced cleaning
(setup item L.14) to avoid continuous cleaning due to the
external trigger. A cleaning action with detergent can be fol-
lowed by one or more actions without detergent, when desired.
Simple cleaning actions are performed in the following order:
• Rinsing time: the device enters hold mode; all relays con-
figured for simple cleaning are energized. If the device is in
normal measurement mode, the "rinSinG" message scrolls
on the LCD; otherwise (i.e. the device is in setup mode) the
cleaning is performed, but no message appears.
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