19
Temperature
Compensation
!Note: Automatic temperature compensation
only functions properly if a temperature probe
is connected.
Temperature compensation influences the results
in two different ways:
1. pH values of the buffers change as a function
of temperature.
Each buffer varies as a function of the tempera-
ture of the respective solution. Typically, these
values are indicated on the buffer label. The
values detailed in the table below apply to most
technical buffers.
If standardization is performed in the pH mode,
the pH value is adapted to the nominal value of
the current temperature.
For example, if the buffer has a nominal pH of
7.00 at a temperature of 25°C, the meter will
standardize the buffer to 7.02 instead of 7.00 at
a temperature of 20°C.
2. Electrode slope changes as a function of
temperature.
Theoretically, the change of voltage per pH unit
is approx. 59.16 mV at 25°C. However, this mV
per pH unit changes as a function of temperature.
The meter compensates for these changes by
taking into account the temperature dependency
of the Nernst factor when calculating pH values.
Standard buffers:
pH 4.00 pH 7.00 pH 10.00
0°C 4.005 7.13 10.34
5°C 4.003 7.10 10.26
10°C 4.001 7.07 10.19
15°C 4.002 7.05 10.12
20°C 4.003 7.02 10.06
25°C 4.008 7.00 10.00
30°C 4.010 6.99 9.94
35°C 4.020 6.98 9.90
40°C 4.030 6.97 9.85
50°C 4.061 6.97 9.78
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