ATI
Q45D Portable Dissolved Oxygen
Part 6 - Calibration
6. If accepted, the screen will display the message
PASS
with the new sensor zero
reading (offset), 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 value for sensor
offset is -40 mV to +40 mV. Should a FAIL occur, carefully inspect the sensor for
a tear in the membrane. It will probably be necessary to rebuild the sensor as
described in section 4.1, Dissolved oxygen Sensor Assembly. Should the offset
value remain high and result in calibration failures, review the Service section of
this manual, and then contact the service dept. at ATI for further assistance.
The sensor offset value in mV from the last zero calibration is displayed on the
lower line of the Default Menus for information purposes.
6.5
TemperatureCalibration
The temperature calibration sequence is essentially a 1-point offset calibration that allows
adjustments of approximately ±5 °C. The sensor temperature may be calibrated on line,
or the sensor can be removed from the process and placed into a known solution
temperature reference.
In any case, it is critical that the sensor be allowed to reach temperature equilibrium with
the solution in order to provide the highest accuracy.
When moving the sensor between widely different temperature conditions, it may be
necessary to allow the sensor to stabilize as much as one hour before the calibration
sequence is initiated. If the sensor is on-line, the user may want to set the output HOLD
feature prior to calibration to lock out any output fluctuations.
1)
Scroll to the CAL menu section using the MENU key and press ENTER or the UP
arrow key.
2)
Press the UP arrow key until
Cal Temp
is displayed.
3)
Press the ENTER key. The message
Place sensor in solution then press
ENTER
will be displayed. Move the sensor into the calibration reference (if it
hasn’t been moved already) and wait for temperature equilibrium to be achieved.
Press ENTER to begin the calibration sequence.
4)
The calibration data gathering process will begin. The message
Wait
will flash
as data is accumulated and analyzed. The
°C
or
°F
symbol may flash
periodically if the reading is too unstable.
5)
The message
Adjust value - press ENTER
will be displayed, and the right-most
digit will begin to flash, indicating that the value can be modified. Using the UP
and LEFT arrow keys, modify the value to the known ref solution temperature.
Adjustments up to ± 5 °C from the factory calibrated temperature are allowed.
Press ENTER.
6)
Once completed, the display will indicate
PASS
or
FAIL
. If the unit fails, the
temperature adjustment may be out of range, the sensor may not have achieved
complete temperature equilibrium, or there may be a problem with the
temperature element. In the event of calibration failure, it is recommended to
attempt the calibration again immediately.
