ATI
Q45D Portable Dissolved Oxygen
Part 6 - Calibration
5. 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. 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
Cal Unstable
will be displayed.
6. The screen will display the last measured ppm value and a message will be
displayed prompting the user for the lab value. The user must then modify the screen
value with the arrow keys and press ENTER. The system then performs the proper
checks.
7. If accepted, the screen will display the message
PASS
with the new 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.
6.3
Dissolved Oxygen Span Cal (sat)
This is the recommended method; however, it requires that the sensor be removed from
the process and cleaned. Once cleaned, the sensor is placed in air known to be at 100%
relative humidity. To accomplish this easily, ATI recommends the use of a calibration bag
to provide a stable high humidity environment. As the sensor temperature equilibrates in
the air cal bag, the transmitter automatically calculates the new 100% saturation point
utilizing the temperature readings and the barometric pressure user data. This method
therefore requires no user input during calibration. Note: It is very important to allow
enough time for the sensor to completely temperature equilibrate with the surrounding air.
This time is at least 10 minutes.
This method requires that the sensor be removed from the process, cleaned, and
covered with a calibration bag. The sensor must also be wet for this procedure.
This method requires no user input during calibration; however, if this is the first time the
system is being installed and calibrated, make sure to enter the proper atmospheric
pressure data and process conductivity data prior to calibration.
1. Remove the sensor from the application. Rinse and clean if necessary.
2. Cover the sensor cartridge using one of the ATI air calibration bags. The end of
the sensor should be wet, and the membrane should not touch the sides of the
bag. If there is water in the bag, the membrane must not be submerged - it must
be in the air. Secure bag firmly around the sensor with a rubber band and let the
sensor hang, membrane downward, while powered.
3. Allow the system to operate undisturbed for at least 20 minutes. If the system is
stable, the value on the display will increase to some PPM value and remain at
that level. At that point, calibration can continue.
4. 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.
5. 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 zero calibration. Using the UP arrow
key, set for a
2-sat
span calibration and press ENTER.
