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MODEL SOLU COMP II
SECTION 6.0
CALIBRATION
6.3.3 Procedure — Calibrating the sensor in air
1.
Remove the sensor from the process stream. Use a soft tissue and a stream of water from a wash bottle to
clean the membrane. Blot dry. The membrane must be dry during air calibration.
2.
Pour some water in a beaker and suspend the sensor with the membrane about 0.5 inch (1 cm) above the
water surface. To avoid drift caused by temperature changes, keep the sensor out of the direct sun.
3.
Monitor the dissolved oxygen reading and the temperature. Once readings have stopped drifting, begin the cal-
ibration. It may take 5 - 10 minutes for sensor reading in air to stabilize. Stabilization time may be even longer
if the process temperature is appreciably different from the air temperature. For an accurate calibration, tem-
perature measured by the sensor must be stable.
4.
Press MENU. The main menu screen appears. Choose Calibrate.
5.
Choose Sensor 1 (dissolved oxygen). For a single sensor configuration,
this screen will not appear.
6.
Choose Measurement.
7.
Choose AirCal.
8.
The screen shows the barometric pressure. If the pressure sensor inside
the analyzer is being used, the display is the current pressure. If the pres-
sure sensor is not being used, the display is the barometric pressure last
entered by the user. If the reading is wrong, enter the correct value.
NOTE
If pressure is being measured by the analyzer, entering a
value will standardize the pressure sensor.
9.
The screen at left appears. The top line is the current dissolved oxygen
reading based on the previous calibration or, for a first time calibration,
the default sensitivity.
10. Once the reading is stable (drift or noise less than 0.05 ppm in 10 sec-
onds), the screen at left appears. Air calibration is complete. Press MENU
then EXIT to return to the main display.
11. During calibration, the analyzer stores the measured current and cal-
culates the sensitivity. Sensitivity is the sensor current in nA divided by the
saturation concentration of oxygen in ppm. The table gives typical sensi-
tivity for Rosemount Analytical dissolved oxygen sensors.
To view the sensitivity, press MENU then EXIT to return to the main dis-
play. Press
'
until the sensitivity information screen is showing.
12. This screen appears if the sensitivity is extremely high or low. See Section
8.3 for troubleshooting. Repeat the calibration.
CCaalliibbrraattee
Hold
Program
Display
Calibrate?
SSeennssoorr11
Sensor2
CalSensor1?
MMeeaassuurreemmeenntt
Temp
S1 Air Calibrate
Press:
760mmHg
S1 Live
8.000ppm
Air Cal Done
S1 Live
8.000ppm
AirCal
WWaaiitt
Cal S1?
AAiirrCCaall
InProcess
Zero
Air Cal Failure
Check sensor
Sensor
Current in air at 25°C
Sensitivity (nA/ppm)
499ADO
15-25 uA
1,800-3,100
499A Tr DO
30-50 uA
3,600-6,100
Hx438 and Gx448
40-80 nA
4.8-9.8