What's the effects of temperature on pH measurement?

What are the effects of temperature on pH measurement?

Temperatures Above 25°C: temperature compensation lowers high pH and raises low pH, resulting in value closer to neutral. Temperatures Below 25°C: temperature compensation raises high pH (more basic) and lowers low pH (more acidic), resulting in values further away from neutral. Whether or not temperature compensation needs to be used is a matter of the needed pH accuracy. For example, if the accuracy requirement is ±0.1 pH, at a pH of 6 and a temperature of 45°C (113°F), the error is 0.06, well within the accuracy requirements. On the other hand, with the same ±0.1 pH accuracy requirement, operating at pH 10 and 55°C (131°F) would give an error of 0.27 pH and compensation should be used.

When compensation is required, it can be done in one of two ways. If the temperature fluctuates, then an automatic temperature compensation should be used. If the temperature is constant within several degrees C, then a manual temperature compensation can be used. If no compensation is needed, a fixed resistor can be installed across the temperature compensation terminals. Any of the above devices–automatic compensation, manual compensation or fixed resistor–operate as a function of the pH meter’s electronic circuit. As such, information and parts should be obtained from the pH meter manufacturer. If automatic compensations are used, they should always be at the same location as the pH electrode.

When pH electrodes are calibrated in buffer, the temperature compensation also should be in the buffer. In a similar way, a manual temperature compensation should be adjusted to reflect the temperature to which the pH electrode is exposed during both calibration and operation.

Temperature Compensation of pH electrode

Temperature compensation is contained within the ph instrument, because pH electrodes and measurements are temperature sensitive. The temperature compensation may be either manual or automatic. With manual compensation, a separate temperature measurement is required, and the pH meter manual compensation control can be set with the approximate temperature value. With automatic temperature compensation (ATC), the signal from a separate temperature probe is fed into the pH sensor, so that it can accurately determine the pH value of the sample at that temperature.

Temperature compensation is contained within the instrument, because pH electrodes and measurements are temperature sensitive. The temperature compensation may be either manual or automatic. With manual compensation, a separate temperature measurement is required, and the pH meter manual compensation control can be set with the approximate temperature value. With automatic temperature compensation (ATC), the signal from a separate temperature probe is fed into the pH meter, so that it can accurately determine the pH value of the sample at that temperature.

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