ATI
PQ45P pH System
Part 7
– DataLogger
30
O&M Manual
Rev-B (7/15)
2. If the sensor has been removed and placed into a buffer, allow sensor to temperature
equilibrate with the buffer as much as possible. With the sensor coming from an application
which differs greatly in temperature difference, the user may have to wait as much as 20
minutes. 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.
3. Scroll to the CAL menu section using the MENU key and press ENTER or the UP arrow key.
Cal pH
will then be displayed.
4.
Press the ENTER key. The screen will display a flashing 1 for 1-point or a 2 for 2-point
calibration. Using the UP arrow key, set for a 1-point calibration and press ENTER.
5. The system now begins acquiring data for the calibration value. As data is gathered, the
units for pH 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 pH value [or the auto buffer value, if activated] 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 offset 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.
5.4
Temperature Calibration
The temperature input is factory calibrated for the highest accuracy. Temperature calibration is
not recommended; however, it is provided for applications in which very long cable lengths are
needed. For example, at 50 feet, readings may be off ±0.2 °C.
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 (see
section 4.66) feature prior to calibration to lock out any output fluctuations.
