Because pH calibrations will drift over time, periodically creating a new custom calibration provides more accurate readings. Vernier pH sensors have the ability to create a custom calibration and store it in the sensor's memory. By default, this stored, custom calibration will be used when the sensor is connected to any device.
In order to do a calibration of the pH Sensor, or to confirm that a saved pH calibration is accurate, you need to have two pH buffer solutions that cover the range of pH values you will be measuring. We recommend buffer solutions of pH 4, 7, and 10.
Once completed, you can save this calibration to the sensor's internal memory so that your custom calibration will load the next time the sensor is used.
Using Logger Pro or LabQuest App
Perform a Standard Two-Point Calibration
1. Choose Calibrate from the Experiment menu (Sensors menu on LabQuest) and select pH Sensor.
2. Click Calibrate Now to begin the calibration process.
3. Place the pH sensor in the first buffer solution.
4. When the voltage reading displayed stabilizes, enter the known pH value in the Reading 1 box and click Keep to record the value.
5. Remove the pH Sensor from the buffer solution and rinse the tip of the pH Sensor with distilled water.
6. Place the pH Sensor in the second buffer solution.
7. When the voltage reading displayed stabilizes, enter the known pH value in the Reading 2 box and click Keep to record the value.
8. A new calibration has been created, but not saved. This new calibration becomes the current calibration for the sensor.
9a. If you want to use the calibration for the current session only, click Done (OK on LabQuest) to complete the calibration process.
9b. If you want to save this custom calibration onto the pH Sensor, follow the appropriate steps below.
Saving Custom Calibration to the pH Sensor's internal memory
In Logger Pro:
1. Click the Calibration Storage tab.
2. Click Set Sensor Calibration.
3. Click Set to confirm the settings
4. Click Done to complete the process.
1. Tap on the Storage tab
2. Tap Save Calibration to Sensor.
3. Tap OK to confirm the settings
4. Tap OK to complete the process.
The sensor will now load this calibration each time it is used on any device.
Using Graphical Analysis 4 for Windows, MacOS, iOS, Chrome, or Android
If you have a Go Direct sensor, once you have performed a two-point calibration as described here TIL 3631: How do I manually calibrate my sensor in Graphical Analysis 4?, the calibration is automatically stored and used the next time the sensor is used. You can always reset the the calibration by selecting Restore Factory Defaults.
If you have a standard sensor, the calibration cannot yet be stored using this software.
TIL 1361: pH Sensor Troubleshooting and FAQs