12.6.3 Temperature Compensation
The slope of a pH electrode (section 12.6.2) is affected by temperature. This
effect is compensated for either by using an Automatic Temperature
Compensation (ATC) probe or by entering the sample temperature manually.
Figure 12-3 shows the slope of a pH electrode at various temperatures.
-600
-400
-200
0
200
400
600
0 7 14
Electrode
Potential (mV) at
0 oC (54mV/pH)
Electrode
Potential (mV) at
50 oC (64mV/pH)
Electrode
Potential (mV) at
100 oC (74mV/pH)
pH Electrode Response, as a Function of Temperature
pH
Figure 12-3
12.7 Checking the reference junction of a pH electrode.
If pH readings are inaccurate or unstable, the reference junction of the electrode
may be blocked. The following test can be performed to determine if the
reference junction of a pH electrode is making adequate contact with the sample
solution.
1. Calibrate the MC-81, as per section 5.1.
2. Dilute 1 part of pH6.88 buffer with 9 parts of distilled water.
3. Measure the pH of the diluted buffer. The result should be 7.06 +/-0.05 pH.
4. If the value obtained is outside of these limits, then clean the reference
junction, as per the instructions supplied with the pH electrode.
5. Re-calibrate the MC-81 and repeat the test.
6. If the value obtained is still outside 7.06 +/-0.05 pH, then the electrode should
be replaced.
To Next Page
Loading...
