A pH meter is an electronic device used for measuring the pH (acidity or alkalinity) of a liquid (though special probes are sometimes used to measure the pH of semi-solid substances). A typical pH meter consists of a special measuring probe (a glass electrode) connected to an electronic meter that measures and displays the pH reading.
In chemistry, pH is defined as the negative logarithm of the hydrogen-ion activity. More simply, it is a measure of the relative amount of free hydrogen (H+) and hydroxyl ions (OH-). That is, it tells the degree to which something – such as soil, water, or any solution – is basic or acidic. pH is reported in logarithmic units, like the Richer scale, which represents strength or earthquakes. Each number represent a tenfold change in the acidity or alkalinity of a substance. The range goes from 0 to 14, and around 7 is considered neutral. Additionally, pH of less than 7 indicates acidity, whereas a pH of greater than 7 indicates alkalinity or a base.
The probe is a key part of a pH meter, it is a rod like structure usually made up of glass. At the bottom of the probe there is a bulb, the bulb is a sensitive part of a probe that contains the sensor. Never touch the bulb by hand and clean it with the help of an absorbent tissue paper with very soft hands, being careful not to rub the tissue against the glass bulb in order to avoid creating static. To measure the pH of a solution, the probe is dipped into the solution. The probe is fitted in an arm known as the probe arm.
Why we need to know?
- Optimal plant growth dependent on soil pH because it effects the availability of all plant nutrients.
- The main use of pH in a water analysis is for detecting abnormal water. The normal pH range for irrigation water is from 6. To 8.4. An abnormal value warning that the water needs further evaluation.
- Irrigation water with pH outside the normal range may cause a nutritional imbalance or may contain a toxic ion.