ATI
Q45D Portable Dissolved Oxygen
Part 6 - Calibration
6. The display will prompt the user to hold the sensor in air and press ENTER. If
the sensor has already been removed, reached temperature equilibrium, and the
calibration bag has been installed, press the ENTER key.
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
CalUnstable
will be displayed.If accepted,
the screen will display the message
PASS
with the new sensor slope reading,
and 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.
The range of acceptable values for sensor slope is 20% to 250%. It may be
necessary to rebuild the sensor as described in section 4.1, 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.
6.4
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 4.1, 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. Cleanand rinse if required.
2. Place about an inch of zero solution in a small beaker orother convenient
container and immerse the tip of thesensor. Allow the sensor to sit undisturbed
for at least 1 hour. Suspend sensor, DONOT LET SENSOR SIT ONTIP.
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 calibration, or a
3-zer
for zerocalibration. Using the UP arrow
key, set for a 3
-Zer
zero calibrationand press ENTER.
5. The system now begins acquiring data for the sensor zerocalibration 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.If the data remains
unstable for 10 minutes, the calibration will fail and the message
CalUnstable
will be displayed.
