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Appendix 3, pH temperature dependency
The output from a pH-electrode varies with the temperature in a predictable way. The
size of the variation depends on both the temperature and the pH being measured.
ºC ºF
PH pH pH pH pH pH pH PH pH
pH
pH
pH
5
41
2.30 3.24 4.18 5.12 6.06 7.00 8.06 9.12 10.18 11.24 12.30 13.36
15
59
2.15 3.12 4.09 5.06 6.03 7.00 8.03 9.06 10.09 11.12 12.15 13.18
25
77
2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00
35
95
1.85 2.88 3.91 4.94 5.97 7.00 7.97 8.94 9.91 10.88 11.85 12.82
45
113 1.70 2.76 3.82 4.88 5.94 7.00 7.94 8.88 9.82 10.76 11.70 12.64
55
131 1.55 2.64 3.73 4.82 5.91 7.00 7.91 8.82 9.73 10.64 11.55 12.46
65
149 1.40 2.52 3.64 4.76 5.88 7.00 7.88 8.76 9.64 10.52 11.40 12.28
75
167 1.25 2.40 3.55 4.70 5.85 7.00 7.85 8.70 9.55 10.40 11.25 12.10
85
185 1.10 2.28 3.46 4.64 5.82 7.00 7.82 8.64 9.46 10.28 11.10 11.92
95
203 0.95 2.16 3.37 4.58 5.79 7.00 7.79 8.58 9.37 10.16 10.95 11.74
At pH 7 or 78
°
F the temperature error is zero. If temperature or pH changes the
temperature eror is calculated using the following formula: 0.03 pH-difference / pH /
10
°
C. pHX has a built in compensation for the temperature error provided that the
correct temperature of calibration buffers and measured media is entered..
