How to Calibrate a PH Pen

A pH pen is a tool commonly used to test the pH balance of various solutions.

pH stands for "potential for hydrogen." The pH scale is used to test the acidity or alkalinity of a solution by measuring it on a scale from 0 to 14. According to the pH scale, a solution measuring 7 is neutral. The greater the value over 7, the more basic the solution; the lower the value under 7, the more acidic the solution. A pH pen is commonly used to test the pH balance of various solutions, but the tool must be properly calibrated to ensure an accurate reading.

Things You'll Need

• pH Pen
• Buffer or reference solution with a pH of 7
• Glass beaker or container
• Distilled water
• Squeeze bottle
• Soft tissue
• Jewelry screwdriver

Instructions

1. Rinse the pen's electrode, which is the glass probe at the end of the pen, by pouring distilled water onto it from a squeeze bottle.

2. Gently blot the electrode dry with a soft tissue. Ensure that there is no water left on the electrode.

3. Turn the pen on by clicking the "on" button found at the top of the pen.

4. Immerse the pen into the glass beaker containing the reference solution with a pH of 7.

5. Gently stir the pen in the solution while waiting for the reading to stabilize.

6. Use the screwdriver to turn the small screw in the hole in the back of the pen until the pen reads precisely "7."

7. Remove the pen from the reference solution and rinse the electrode again with distilled water. Wipe it again with a soft tissue.

Tips & Warnings

• When traveling from one site to another for pH testing, bring a reference solution with you to maintain an accurate calibration on the pen. Every time you immerse the pen in a new solution, recalibrate the pen.

• Do not touch the electrode when calibrating the pen, particularly after rinsing it with the distilled water; oil from your fingertips can negatively affect the accuracy of the calibration.

References

• GLOBE in the City, UCLA Institute of the Environment
• Aquatic Quotient
• WordNet Web