Analog Output - Hanna Instruments HI 504 Instruction Manual

All the alarm signals (red LED, alarm relay, fault currents) are
suspended while in hold mode (the correspondent error events
are not closed), unless the hold mode is being triggered by
one or more errors and no other trigger source (different from
an error) is active.
The analog output follows these rules:
• if it is configured for control (i.e. setup item O.10 or O.20
set to "SEt"), its value is set to the minimum (e.g. 4 mA for
4-20 mA output);
• if it is configured for a recorder, its value is either set to a
user-selected value through the setup item O.15 or O.25
(when item O.14 or O.24 is set to "USEr") or frozen to the
last value, i.e. the output value just before entering the
hold mode (when item O.14 or O.24 is set to "HOLd").
After the cause which made the instrument enter the hold
mode expires, the device exits hold mode but control and
alarms remain disabled for a delay which can be user-se-
lected (0 to 99s) through setup item C.70. In that situation
measurements are normally acquired, displayed and recorded
through the analog output or the RS485.
Note
Alarms (red LED, alarm relay, fault currents) are not disabled
if the hold mode is being triggered by an error and no other
trigger source is active.
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ANALOG OUTPUT

The meter is provided with two insu-
lated current outputs.
It is possible to configure the operating mode of each output
through setup menu (items O.10 and O.20).
If the meter is configured as an ORP controller, the output
#2 can be enabled to operate in control mode only (setup
item O.20 set to "SEt"; see the "Control through analog out-
put" section for more details).
If the meter is set as a pH controller, each available output
can be used as recorder or in control mode.
To configure an output to control mode the corresponding
item (O.10 for output #1 and O.20 for output #2) has to be
set to "SEt" (see the "Control through analog output" section
for more details).
When set to recorder (setup item O.10 or O.20 set to
"rECO"), the output #1 gives a current signal proportional
to the actual pH value, while the output #2 gives a signal
proportional to the temperature value.
By default, the minimum and maximum values of analog
output correspond to the minimum and maximum of meter's
range. For example, for a selected analog output of 4-20
mA associated to output #1, the default values are -2.00
and 16.00 pH corresponding to 4 and 20 mA respectively.
These values can be changed by the user to have the analog
output matching a different pH range; for example, 4mA =
3.00pH and 20mA = 5.00pH.
To change the default values, enter the setup mode and
change the items O.12 and O.13 for output #1, and O.22
and O.23 for output #2.
The analog output signal range (0-20 mA or 4-20 mA) of
each output is also selectable through the setup items O.11
and O.21.
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