Yokogawa EXAxt PH450 4-Wire Analyzer for pH and ORP - Manual (Page 19)

11
IM 12B07C05-01E
3
INSTALLATION
AND
WIRING
3-4. Wiring the contact signals
3-4-1. General precautions
The contact output signals consist of volt-
age-free relay contacts for switching electrical
appliances (SPDT). They can also be used as
digital outputs to signal processing equipment
(such as a controller or PLC). It is possible to
use multi-core cables for the contact in and
output signals and shielded multi-core cable for
the analog signals.
3-4-2. Contact outputs
The EXAxt 450 unit’s four contacts (switches)
that can be wired and configured to suit user
requirements. Contact S4 is programmed as
a fail-safe contact. Please refer to section 5-8,
Contact output setup for functionality descrip-
tion.
Alarm (limits monitoring)
Contacts configured as “ALARM” can be ener-
gized when limits are crossed.
Fail
Contacts configured as “FAIL” will be energized
when a fail situation occurs. Some fail situa-
tions are automatically signaled by the internal
diagnostics (electronics) of the converter.
Others can be configured by the user (see
section 5-11 Error Configuration). By pressing
the “INFO” button on the main screen the user
is given an explanation as well as a remedy for
the current fail situation.
Always connect the fail contact to an alarm
device such as a warning light, alarm bell or
displayed on an annunciator.
“ALARM” Contact “FAIL” Contact
Power Off NC NC
Power On NC NC
Alarm NO NC
Fail NC NO
Fail and Alarm NC* NO
HOLD** NC NC
* When a fail situation occurs which is related
to the parameter associated with the contact
(pH, ORP, rH or temperature) the contact
will go to NC. When the fail situation is not
related to the parameter associated with the
contact the contact will remain in the state it
is currently in.
** Wash cycles do not influence other contacts.
When HOLD is enabled during wash, it is
HOLD that will set all contacts to NC.
3-4-3. Contact input
It is necessary to use screening/shielding on
the input signal cables. Terminal 63 is used to
connect the shielding.
3-5. Wiring the mA-output signals
3-5-1. General precautions
The analog output signals of the EXAxt
transmit low power standard industry signals to
peripherals like control systems or strip-chart
recorders (Figure 3-6).
3-5-2. Analog output signals
The output signals consist of active current
signals of 4-20 mA. The maximum load can be
600 ohms on each.
It is necessary to use screening/shielding on
the output signal cables. Terminal 63 is used to
connect the shielding.
Figure 3-8-a. External grounding Figure 3-8-b. Internal grounding
2
N
1
L
POWER
100-240 VAC/15 VA/ 50/60Hz
FUSE: 500 mA/250 VAC/T
AC
(M4 screw)
(M4 screw)