Standard buffer:
pH 4.00 pH 7.00 pH 10.00
0 °C
4.005
7.13
5 °C
4.003
7.10
10 °C 4.001
7.07
15 °C 4.002
7.05
20 °C 4.003
7.02
25 °C 4.008
7.00
30 °C 4.010
6.99
35 °C 4.020
6.98
40 °C 4.030
6.97
50 °C 4.061
6.97
20
Temperature Compensation
!
Note: The temperature is compensated automatically
only if an ATC probe is connected.
Temperature has two major effects on pH values:
1. Temperature affects buffer pH values.
The pH value in a buffer is dependent on the tempera-
ture of the buffer. The values are usually given on the
buffer label. Most technical buffers correspond to the
values listed in the table shown here on the left.
When you perform standardization in pH mode, the pH
value is adjusted to the current value for the current
temperature.
For example, if the buffer has a pH of 7.00 at 25°C and
the current buffer temperature is 20°C, the portable
meter standardizes the buffer at pH 7.02.
10.34
2. Temperature affects electrode efficiency.
10.26
The theoretical voltage change per pH unit is
10.19
approximately 59.17 mV at 25°C. This value changes,
10.12
however, as the temperature changes.
The meter compensates for this effect by changing the
10.06
pH reading as the temperature changes
10.00
9.94
9.90
9.85
9.78