What causes errors in pH sensor readings?

One of the most common causes of error in pH measurement is electrode drift. This occurs when the pH electrode becomes less sensitive over time, causing the meter to give readings that are either consistently higher or lower than the actual pH of the sample. This can be caused by a variety of factors, such as aging of the electrode, contamination of the electrode surface, or changes in the internal electrolyte solution. To minimize the effect of electrode drift, pH electrodes should be regularly calibrated and replaced according to the manufacturer’s recommendations. Additionally, it is important to carefully clean and store the electrode when not in use to prevent contamination.

Also, temperature is a major cause for pH errors in measurement. The pH of a solution is strongly influenced by its temperature, and a change in temperature can cause the pH reading to be inaccurate. This is because the concentration of hydrogen ions in a solution is affected by temperature, and the pH scale is based on the concentration of hydrogen ions. In order to minimize the effect of temperature on pH measurement, it is important to carefully control the temperature of the sample being tested and to use a pH meter that is designed to compensate for temperature variations. Some pH meters have built-in temperature sensors and automatic temperature compensation, which can help to reduce the error caused by temperature changes.

Another technical cause of error in pH measurement is the presence of ionic strength-adjusting agents (ISAs) in the sample being tested. ISAs are chemicals that are added to a sample to adjust its ionic strength, which can affect the accuracy of the pH reading. This is because the concentration of hydrogen ions in a solution is influenced by the presence of other ions in the solution, and ISAs can change the concentration of ions in the sample. In order to minimize the effect of ISAs on pH measurement, it is important to carefully control the concentration of ISAs in the sample and to use a pH meter that is designed to compensate for the presence of ISAs. Some pH meters have built-in ISA compensation, which can help to reduce the error caused by the presence of ISAs in the sample.

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