Specifications
MODEL 30 pH/DO SECTION 6.0
CALIBRATION
35
6.3.2 Procedure — Zeroing the sensor.
1. Place the sensor in a fresh solution of 5% sodium sulfite (Na
2
SO
3
) in water. Be sure air bubbles are not
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 and press ' until the sensor input current is show-
ing.
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.
2. Press MENU. The main menu screen appears. Choose Calibrate.
3. Choose Sensor 1 (dissolved oxygen). For a single sensor configuration,
this screen will not appear.
4. Choose Measurement.
5. Choose Zero.
6. 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.
7. Once the reading is stable, the screen at left appears. Sensor zero is
complete and the analyzer has stored the zero current. The screen
remains until the operator presses MENU then EXIT to return to the main
display.
NOTE
Pressing ENTER during the zero step will cause the analyz-
er to use the present sensor current as the zero current. If the
sensor is zeroed before the current has reached a minimum
stable value, subsequent readings will be in error.
After zeroing, leave the sensor in the zero solution and verify that the sen-
sor current agrees with the value shown in the table. To display the sen-
sor current, go the the main display and press 'until the input current is
showing.
8. This screen appears if the zero current is extremely high. See Section 8.3
for troubleshooting.To repeat the zero step, press EXIT and choose Zero.
9. This screen appears if the zero current is moderately high. To continue,
choose Yes. To repeat the zero step, choose No.
CCaalliibbrraattee
Hold
Program Display
Calibrate?
SSeennssoorr11
Sensor2
CalSensor1?
MMeeaassuurreemmeenntt
Temp
S1 Live 1.000ppm
Zeroing
WWaaiitt
Sensor Zero Fail
Current Too High
S1 Live 0.000ppm
Sensor Zero Done
Cal S1? AirCal
InProcess
ZZeerroo
Possible ZeroErr
Proceed? Yes
NNoo