Emerson Process Management OXYMITTER 4000 IM-106-340 - Manual (Page 68)

Oxymitter 4000
4-6
Instruction Manual
IM-106-340, Rev. 4.0
May 2006
Recommended
Configuration Recommended Configuration
4-20 mA Signal
The 4-20 mA signal is linear, and can be ranged by the user for O
2
range from
0-40% O
2
. It should be noted that the 4-20 mA signal will go to one of several
default values under certain conditions:
It is very important that the control system be configured to recognize these
various signal levels, and operators be briefed as to their meaning.
Calibration
Rosemount Analytical recommends utilizing 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 life. This strategy ensures that the O
2
reading is always accurate, and eliminates many unnecessary calibrations
based on calendar days or weeks since previous calibration. When utilizing
the SPS 4001B or IMPS 4000, consider wiring some or all associated alarm
contacts.
1. CALIBRATION INITIATE. Contact from the control room to an SPS
4001B or IMPS 4000 (one per probe) provides the ability to manually
initiate a calibration at any time from the control room. Note that
calibrations can also be initiated from a HART handheld communicator,
from Asset Management Solutions software, or from the keypad on the
Oxymitter 4000.
2. IN CALIBRATION. One contact per probe provides notification to the
control room that the "calibration recommended" diagnostic has initiated
an automatic calibration through the SPS 4001B or IMPS 4000. If the O
2
signal is being utilized in an automatic control loop, this contact should
be utilized to place the control loop into manual during calibration.
3. CALIBRATION FAILED. One contact per probe from an SPS 4001B or
IMPS 4000 to the control room for notification that the calibration
procedure failed. Grouped with this alarm is an output from a pressure
switch which indicates when the calibration gas bottles are empty.
4. 4-20 mA SIGNAL DURING CALIBRATION. The 4-20 mA signal can be
configured to respond normally during any calibration, or it can be
configured to hold the last O
2
value upon the initiation of calibration. The
factory default is for the 4-20 mA signal to track (operate normally)
throughout calibration. Holding the last O
2
value may be useful if
several probes are being averaged for the purpose of automatic control.
Unless several probes are being averaged, always place control loops
that are using the O
2
signal into the manual mode prior to starting the
calibration.
Condition Default Option
In calibration 4-20 mA signal responds
normally to cal gas 4-20 mA signal holds last value during
cal. (recommended only if several O
2
probes are being averaged together)
O
2
over preset
range
4-20 mA signal defaults to
20.5 mA none
Critical alarm 4-20 mA signal defaults to
3.5 mA 4-20 mA signal dfaults to 21.1 mA
Dead Instrument 4-20 mA signal goes to
zero mA none