Using the pH Probe

Preparation of the pH Sensor

A pH sensor connected to a computer will be used to measure pH. Plug the pH probe into channel 1 of the interface box. Plug the power cord on the interface box into an electrical outlet.

Click on the photograph to view an enlargement.

Start Logger Pro by double-clicking the icon (if available) or clicking Programs - Vernier Software - Logger Pro.

The pH meter is displayed at the bottom left side of the screen. We will not use any of the graphing or data collection capabilities of Logger Pro.

Checking and Using the pH Sensor

The probe tips age and occasionally need to be replaced, especially if they have become dry. Use the procedure described below to check your probe by measuring the pH of two different solutions that have a known pH. Inform your instructor if the pH differs by more than 0.5 units from the known pH. 

1.  The probe tips are kept in a storage solution to keep them moist and protect them. Unscrew the small bottle and rinse the probe by immersing it in deionized water as shown in the photograph below. When not being used, the probe should be kept in the water to prevent the tip from becoming dry.

2. After the probe has been thoroughly rinsed verify that it works by using the two solutions of known pH that have been provided. Place the tip in a solution with a known pH of 3.0 or 4.0. The pH reading will be displayed on the computer screen in the area labeled "pH-Live." The reading will fluctuate for a short period of time. Slowly swirl the solution with the probe until the reading stabilizes. Verify that the pH reading is approximately the same as the known pH.

The probe should be thoroughly rinsed each time it is moved from one solution to another. This can be done by immersing the probe in a beaker of deionized water.

3. Remove the probe from the solution, rinse it thoroughly by immersing it in a beaker of distilled water and swirling it. The probe should be kept submerged in the water when it is not used.

4. Transfer the probe to a solution with a known pH of 8.0 or 10.0. Slowly swirl the solution with the probe until the reading stabilizes. Again, verify that the pH reading is approximately the same as the known pH.

4. When finished, rinse the sensor with distilled water before returning it to the pH electrode storage solution.