What is a pH Meter?
pH meters are devices used to measure Hydrogen (H) ion activity in solutions. In other words, the pH meter is used to measure the acidity and alkalinity values in a solution. The degree of hydrogen ion activity is generally in the pH range of 1 to 14.
The pH measurement is directly related to the ratio of hydrogen ion concentration [H+] and hydroxyl ion concentration [OH-]. For pH levels
- Neutral solution: pH = 7
- Acidic solution: pH < 7
- Basic solution: pH > 7
In a neutral solution, hydrogen and hydroxide ions show equal activity, so pH is measured at 7.
In pH measurements in acidic solutions, hydrogen ion activity is greater than hydroxide ion activity, so pH is measured below 7.
In basic (alkaline) solutions, on the other hand, the hydroxide ion activity is higher than the hydrogen ion, so the solutions exhibit pH levels above 7 in measurements made with a pH meter.
How does the pH Meter Work?
A pH meter consists of three main parts, an internal electrode, a reference electrode, and a high input impedance meter. The glass probe usually contains two electrodes, the internal electrode and the reference electrode. The probe contains a buffer solution with a pH of 7. The pH value measured with a pH meter is the Hydrogen [H+] difference between the reference buffer in the probe and the sample solution.
