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Troubleshooting
Example 1: pH Negative offset – Reading Too Low
Step
Description
Step 1
Initial test
Step 2
Reducing offset by
mixing buffers
Normal calibration
Step 3
(1 of 3)
Normal calibration
Step 4
(2 of 3)
Step 5
Normal calibration
(3 of 3)
Figure 12-2: pH Negative offset - Reading Too Low
Example 2: pH Positive Offset – Reading Too High
Step
Description
Step 1
Initial test
Step 2
Reducing offset by
mixing buffers
Normal calibration
Step 3
(1 of 3)
Step 4
Normal calibration
(2 of 3)
Step 4
Normal calibration
(3 of 3)
Figure 12-3: pH Positive Offset – Reading Too High
Note: Use the measurement from the pH sensor when mixing the buffer solutions.
Buffer solution
Observed pH
7.0
6.5
(90% buffer 7.0 +
Before calibration:
10% buffer 10) =
6.8
buffer 7.3
After calibration:
7.0
7.0
6.7
Before calibration:
7.2
After calibration:
7.0
4.0
4.0
10.0
10.1
Buffer solution
Observed pH
7.0
7.5
(90% buffer 7.0 +
Before calibration:
10% buffer 4) =
7.2
buffer 6.7
After calibration:
7.0
7.0
7.3
Before calibration:
6.8
After calibration:
7.0
4.0
4.0
10.0
10.0
Calibration Data
Conclusion
Not accepted
Offset too big
Accepted.
Offset reduced.
Reading is 7.0
Red LED will
but real value
flash 3 times
should be 6.8
Calibration
Accepted.
Success. Offset
Red LED will
Removed
flash 3 times
Calibration
Accepted.
Success
Red LED will
flash 3 times
Accepted.
Calibration
Success
Red LED will
flash 3 times
Calibration Data
Conclusion
Not accepted
Offset too big
Accepted.
Offset reduced.
Reading is 7.0
Red LED will
but real value
flash 3 times
should be 7.2
Calibration
Accepted
Success
Red LED will
flash 3 times
Offset removed
Accepted
Calibration
Success
Red LED will
flash 3 times
Accepted
Calibration
Success
Red LED will
flash 3 times
Page 70 of 110
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