Emerson Rosemount Oxymitter 4000, Справочное руководство, Страница: 82 / 198

4.5 Logic I/O
You can configure the two-terminal logic contact either as a solid-state relay-activated
alarm or as a bi-directional calibration handshake signal to a Rosemount
™ IMPS 4000 or
SPS 4001B.
The configuration of this signal depends on the setting of the Logic I/O PIN MODE via
HART
® /AMS or LOI. The ten different modes available are explained in Table 2-9 .
4.5.1 Alarm
When configured as an alarm, this signal alerts you to an out-of-spec condition. The
output is +5 Vdc in series with a 340 ohm resistor.
For optimum performance, Emerson recommends connecting the output to a Potter &
Brumfield 3.2 mA DC relay (PN R105-E1Y1-J1.OK).
Of the 10 modes in Table 2-9 , modes 0 through 7 are the alarm modes. The factory default
is mode 5 for a Rosemount
™
Oxymitter 4000 without a Rosemount IMPS 4000 or SPS
4001B. In this mode, the output will signal when a unit alarm or a
CALIBRATION
RECOMMENDED
indication occurs.
4.5.2 Calibration handshake signal
If using an optional Rosemount IMPS 4000 or SPS 4001B, you must configure the logic I/O
for calibration handshaking.
Of the 10 modes in Table 2-9 , only modes 8 and 9 are configured for calibration
handshaking. For a transmitter with a Rosemount IMPS 4000 or an SPS 4001B, the factory
sets the default to mode 8. In this mode, the logic I/O is used to communicate between
the transmitter and the sequencer.
4.6 Recommended configuration
4.6.1 4-20 mA signal on critical alarm
Emerson recommends using the factory default. The 4-20 mA signal will go to the 3.5 mA
level upon any critical alarm, which will cause the O
2
reading to be unstable.
The customer can also select 21.6 mA as the failure setting if normal operations cause the
O
2
readings to go below the zero % O
2
(3.5 mA) level. If using the O
2
measurement as part
of an automatic control loop, place the loop into manual upon this failure event or take
other appropriate action.
4.6.2 Calibration
Emerson recommends using an autocalibration system actuated by the
Calibration
recommended
diagnostic.
New O
2
cells may operate for more than a year, but older cells may require recalibration
every few weeks as they near the end of their lives. This strategy ensures that the O
2
Configure transmitter with LOI Reference Manual
October 2019 00809-0100-4340
82 Emerson.com/Rosemount