ATI
Q45R ORP System
Part 5
–Calibration
30
O&M Manual
Rev-C (7/15)
5.14 1-Point Calibration Explained
The 1-point calibration method is generally known as the "grab sample"
calibration method. In the 1-point calibration method, the sensor may be
removed from the application and placed into the mV solution. It may also be left
in the measurement process and calibrated by reference. 1-point calibration
adjusts only the sensor offset. Since the sensor slope degrades much slower
than the sensor offset, this method may be used as a frequent calibration method
between more involved 2-point calibrations. For example, a user may choose to
perform on-line 1-point calibrations weekly and 2-point calibrations monthly.
5.2
Performing a 2-Point Calibration
Two-point calibration adjusts both the slope and the offset of the sensor. Slope
relates to how closely the system matches displayed mV with actual mV. Offset
is the actual difference over the entire output curve between actual and displayed
mV. Two point calibrations are not recommended for frequent calibrations as the
slope of the ORP sensor does not degrade appreciably over time. However, two-
point calibration does provide the highest level of accuracy.
1.
Remove sensor from application. Rinse and clean if necessary.
2.
Allow sensor to temperature equilibrate with the buffer as best as possible. With
the sensor coming from an application solution that differs greatly in temperature
from the buffer, the user may have to wait as much as 20 minutes for this to
occur.
3.
Scroll to the CAL menu section using the MENU key and press ENTER or the UP
arrow key.
Cal ORP
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 2-point calibration and
press ENTER.
5.
The display will prompt the user to place the sensor in the first mV solution and
press ENTER. If the sensor has been placed into this solution already, once the
temperature has stabilized, press ENTER to continue.
6.
The present ORP value will be displayed and the secondary line of the display
will flash