ATI Q46D Dissolved Oxygen System Part 7 - Calibration
45
O&M Manual
Rev-N (4/21)
7. The system now begins acquiring data for the calibration value. As data is gathered, the
units for ppm and temperature may flash. Flashing units indicate that this parameter is
unstable.
8. The calibration data point acquisition will stop only when the data remains stable for a pre-
determined amount of time (approximately 15-20 seconds.) This can be overridden by
pressing ENTER. If the data remains unstable for 10 minutes, the calibration will fail and the
message Cal Unstable will be displayed.
9. If accepted, the screen will display the message PASS with the new sensor slope reading,
then it will return to the main measurement display. If the calibration fails, a message
indicating the cause of the failure will be displayed and the FAIL icon will be turned on.
10. The range of acceptable values for sensor slope is 20% to 250%. It may be necessary to
rebuild the sensor as described in section 5, Dissolved Oxygen Sensor Assembly.
Should the slope value remain out of range and result in calibration failures, review the Service
Section of this manual, then contact the Service Dept. at ATI for further assistance.
7.14 Dissolved Oxygen Zero Cal
Dissolved oxygen sensors have extremely low offset outputs at zero. For this reason, it is
normally sufficient to simply leave the zero at the factory default of 0 mV. As an alternative, an
electronic zero can be set by disconnecting the sensor from the cable and performing the steps
below.
These steps below assume that the sensor has been prepared in accordance with Section 5,
Dissolved Oxygen Sensor Assembly, earlier in this manual. Note that the 10 hour waiting time in
step 2 below is not required if the monitor has been running for 24 hours prior to zeroing. If the
unit has been running with the sensor connected, the sensor will normally return to a stable zero
within 15 minutes.
1. Remove the sensor from the application if necessary. Clean and rinse if required.
2. Place about an inch of zero solution in a small beaker or other convenient container and
immerse the tip of the sensor. Allow the sensor to sit undisturbed for at least 1 hour.
Suspend sensor, DO NOT LET SENSOR SIT ON TIP.
3. Scroll to the CAL menu section using the MENU key and press ENTER or the UP arrow key.
Cal D.O. will then be displayed.
4. Press the ENTER key. The screen will display a flashing 1-spl for 1-point, a 2-%sat for
Saturation air calibration, or a 3-zer for zero calibration. Using the UP arrow key, set for a 3-
Zer zero calibration and press ENTER.
5. The system now begins acquiring data for the sensor zero calibration value. As data is
gathered, the units for sensor millivolts (mV) and temperature may flash. Flashing units
indicate that this parameter is unstable. The calibration data point acquisition will stop only
when the data remains stable for a pre-determined amount of time. This can be overridden
by pressing ENTER.
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