What is the primary function of a pH probe, and what is its typical output?

• A. It creates an electrical potential when immersed into a sample. The Output is the difference between the mV signals.
• B. It measures color change in the sample.
• C. It generates a digital pulse proportional to pH.
• D. It measures current flow in the solution.

Answer: (A)

The pH probe works as an electrochemical sensor that measures hydrogen ion activity by generating an electrical potential between its glass sensing electrode and a reference electrode when it’s immersed in a solution. The meter reads this voltage and converts it to a pH value. The usual output is a millivolt signal—a small voltage that changes with pH. At room temperature, the change is about 59 mV per pH unit (per the Nernst equation), though the exact slope depends on temperature and electrode condition. This potential, not current or color change, carries the information about acidity. So the best description is that it creates a voltage signal whose millivolt output correlates with pH.