Analytical instruments

Process analyzers

Environmental/Process analyzers

Temperature Compensation Electrodes

The electromotive force of a glass electrode varies depending on temperature, even with a like pH value.

 

E -0.19842 x (273+t) (pHx-pHi) + Ea


The inclination of the straight line on the graph varies in proportion to the temperature (t) in Figure 6, which shows the relation between the pH value of the test solution (pHx) and the electromotive force (E). Therefore, pH cannot be measured correctly without taking into consideration the thermal properties of the glass electrode. The temperature of the glass electrode is compensated by an automatic temperature compensation electrode or by inputting the temperature manually in order to alter the amplification degree to adjust it at 0.1984 mV/deg, per 1 pH. It should be made clear that the temperature compensation of the pH meter is not for compensating the thermal properties of the test solution but for the electromotive force of the glass electrode.

 

The thermal property of the test solution varies depending on the type of solution and cannot be compensated. Therefore, JIS asks to make the temperature different between the reference solution and the test solution within ±1°C for high-accuracy measurement. However, the capability of the electrode has been improved and, in general, automatic temperature compensation is commonly adopted.

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