11 Calibration
Standard Calibration
Preparation
• On the controller, go to Channel setup, Probe settings to select required buffer group.
• Up to three pH buffers may be used for a calibration.
At least two buffers are required to determine a pH slope.
Note
: It is recommended to select buffers that bracket the expected process pH.
Procedure
One-, two-, or three-point calibration can be performed using buffer solutions selected from one of the two
buffer groups. It is generally recommended to use 7.01 or 6.86 pH buffer as first calibration point. When the
electrode is immersed into buffer solution, the controller automatically recognizes the buffer value.
1. Remove the protective cap.
2. Press the
m
key then
CAL
virtual key, to enter calibration mode.
The first suggested buffer solution “7.01 pH” (using Hanna
®
buffers) or “6.86 pH” (using NIST buffers)
is displayed in the upper left corner of the screen.
3. Immerse the pH probe approximately 4 cm (1½”) into buffer solution and stir gently. The controller
automatically recognizes the standard and the buffer value is displayed.
4. When the reading is stable,
CFM
is displayed
.
Press
CFM
to save.
“Wait” followed by “Calibration point is accepted and saved” is displayed after the calibration point has
been saved and accepted.
5. Select
Next
to continue with a two-point calibration.
6. Repeat step 3.
4.01 pH buffer value is displayed flashing but it will change to the buffer used once recognized.
7. When the reading is stable
CFM
is displayed
.
Press
CFM
to save.
8. Select
Next
,
when prompted, to continue with a three-point calibration.
9. Repeat step 3 using a third buffer.
10. When the buffer is recognized and the reading is stable,
CFM
is displayed
.
Press
CFM
to save calibration.
“Calibration DONE” confirmation screen is displayed next.
To save a one-point or two-point calibration, select
Exit
when prompted.
Note
: One-point calibration evaluates electrode offset whereas a two-point or three-point calibration evaluates
both electrode offset and slope.
Process Calibration
A process calibration is a single point calibration, performed while the probe remains installed in the process.
Users can adjust the measured process pH value (±0.5 pH) so that it matches the value determined with a
reference instrument.
Preparation
Use a calibrated portable meter and probe to determine the process pH value.
Process controller and probe should have previously been calibrated with two standards (probe slope determined).