What they look like

How the sensor works

pH sensors usually comprise two components; a pH electrode and a pH adaptor.
pH sensors use an electrode to measure the concentration of Hydrogen ions in solution.
The pH electrode is actually a combination of two half-cells (electrodes) inside one slender container. The electrolyte surrounding the measuring electrode seeps through a porous membrane to make electrical connection with the sample to be investigated. The voltage of this electrode varies according to the hydrogen activity of the solution, and a second reference electrode provides a stable and constant reference voltage, which completes the electrical circuit. The pH Adaptor measures the difference in voltage between these two electrodes. This millivolt reading is displayed in pH units.

Taking measurements

1. Before use, check calibration.
2. Rinse the electrode thoroughly in distilled water.
3. Place the electrode in the sample and allow sufficient time for it to stabilise before taking readings.
4. Rinse the electrode between each measurement with either a portion of the next sample or a buffer to be measured or with deionised or distilled water.

Practical Information

• Keep the pH sensitive membrane wet at all times.
• Always use freshly prepared pH buffers.
• Avoid handling the pH sensitive glass membrane.
• The electrical connections must be kept clean and dry.
• Provide moderate stirring for faster electrode response.
• Buffers, samples and test solutions should be at the same temperature when measuring pH.

Where it can be used

• Acid - base titration.
• Investigating CO2 production in respiration
• Investigating CO2 production in respiration
• Activity of enzyme.
• Studies of household acids & bases.
• Monitoring pH change during chemical reaction
• Acid rain studies