Image of pH tester for article on automated pH testing.
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Published On: September 26th, 2023Categories: Articles, pH Meter
A pH meter is used to measure the alkalinity or acidity of a substance, usually a solution. The pH scale itself is numbered from 0 to 14, with 0 being the most acidic and 14 being the most basic (alkaline). The principle of a pH meter, or any pH reading, is measuring the hydrogen ion concentration, typically in a water-based solution.Decades ago, researchers would use pH test strips to measure pH, but they are not always accurate. Because knowing the pH of a solution is imperative, pH meters were created so that readings could be more accurate. Today, there are different types of pH meters designed for both fieldwork and the laboratory. Read on to learn more about the principles of pH meters, how a meter works, and how to take care of your meter.

Principles of pH Meters: Different Types of pH Meters

The three primary types of pH meters are benchtops, handheld (wireless) pH meters, and pens. Pens are ideal in fieldwork in limited applications, such as testing a pool or spa, and come as one piece. Other handheld meters have an electrode that is separate from the electrometer. The principles of pH meters that are older involve two separate electrodes: a glass and a reference electrode. Most of today’s models combine the two and include what is called a combination electrode. Benchtop pH meters are typically used in the lab. When choosing a pH meter, discern where you’ll be using it the most, and then consider accuracy and electrode features.

Principles of pH Meters: How a pH Meter Works

The principle of pH meters is wholly based on the ion exchange between the sample and the glass electrode’s inner solution, which generates electrical voltage. The result of the principle of pH meters is based on the hydrogen ion concentration and the relation between electric voltage and the pH reading.

Electrodes are typically made of glass because part of pH meter maintenance is keeping the probe hydrated so that it does not degrade. A pH electrode consists of 

  • A reference junction
  • A glass membrane
  • An electrode body
  • A reference electrode
  • A reference electrolyte

The glass membrane in a pH probe has a buffer solution that allows hydrogen ions to enter the membrane, and the noted differences create voltage potential. The electrodes inside the probe measure this voltage potential that is calcuated to be the pH of the solution.

How to Maintain a pH Meter

Knowing the working principles of a pH meter is important so that you can maintain and take care of it properly. First, before each use, a pH meter should be calibrated for the utmost accuracy. Not calibrating the meter could affect the readings. The electrode should be soaked in deionized or distilled water between each use. To do so, put the electrode in a cleaning solution for 10 to 15 minutes and then rinse with distilled water. While each electrode is different, most manufacturers recommend not wiping down the electrode with a cloth or towel, as this could cause static and affect readings. After the electrode has been rinsed, it should be housed in its storage solution until the next use. This will ensure their longevity if taken care of and stored properly.

To learn more about which meter may be the best fit for your laboratory, request a quote from Hudson Robotics today, and we’ll be in touch as soon as possible.