Procedure - Zeroing The Sensor Using Deltav - Emerson ROSEMOUNT 5081-A Instruction Manual

MODEL 5081-A
9.3 PROCEDURE — zEROING THE SENSOR USING Deltav
1. Place the sensor in a fresh solution of 5% sodium sulfite (Na
trapped against the membrane. the current will drop rapidly at first and then gradually reach a stable zero
value. to monitor the sensor current, go to the main display. Press dIAG followed by NEXt. the SenSor Cur
prompt appears. Press ENtER to view the sensor current. Note the units: nA is nanoamps; mA is microamps.
the table gives typical zero values for Rosemount Analytical sensors.
Sensor
499Ado
499Atrdo
Hx438 and Gx448
A new sensor or a sensor in which the electrolyte solution has been replaced may require several hours (occa-
sionally as long as overnight) to reach a minimum current. do Not StARt tHE ZERo RoutINE uNtIL tHE
SENSoR HAS BEEN IN ZERo SoLutIoN FoR At LEASt tWo HouRS.
2. Access: deltaV Explorer/Context Menu
Zero Amperometric Sensor (method_sensor_zero)
Method Steps:
a. displayed: Current oxygen Measurement
Zero limit
Is PV less than limit?: Yes; No; Abort
Selecting "Yes" to an oxygen measurement greater than the zero limit will cause
the measurement to be accepted as the zero value. Selecting "No" will cause
the oxygen measurement to be re-read. the new oxygen measurement may be
closer to the zero limit. If the oxygen measurement is significantly greater than
the zero limit, the method should be aborted ("Abort") and restarted after suffi-
cient time for the oxygen reading to approach the zero limit.
b. If "Yes" is chosen, the Current oxygen Reading and the new Zero Current Value are displayed. the
method then concludes.
62
Zero Current
<50 nA
<5 nA
<1 nA
So ) in water. Be sure air bubbles are not
2 3
NOTE
SECTION 9.0
CALIBRATION — OxyGEN