What are pH Meters? The Complete Guide



pH meters—also known as potentiometric pH meters—are specialised instruments designed to measure and indicate alkalinity and acidity levels within a water-based solution. 

pH meters play a vital role in a range of industries, assisting with quality control and laboratory experimentation, among other applications.

This article will function as your complete guide to pH meters, explaining what they are, how they work, and how different industries use them.

What is a pH Meter?

A pH meter is a scientific instrument that measures the activity of hydrogen ions in a fluid, which is responsible for the acidity or alkalinity of a substance. 

The pH scale was invented by Danish chemist Søren Sørenson in 1909. He was the first person to develop a reliable instrument for measuring hydrogen-ion concentration.

As the world becomes more aware of the effects industrial chemicals have on our environment, we’ve become more careful about the food, water, and other consumables we use. This has led to an increased need for accurate measurement instruments like industry-grade pH meters.

Types of pH Meters

There are four types of pH meters: electrochemical, photometric, glass electrode and ion selective.

The electrochemical is the most common and affordable option for home use. It uses a platinum or glass electrode to measure hydrogen ions in water. This type of pH meter is accurate and relatively inexpensive, but it has to be calibrated regularly to maintain accuracy.

A photometric pH meter measures the colour change of a special solution as it is exposed to varying levels of acidity or alkalinity. These devices are more expensive than electrochemical pH meters, but they don’t require calibration. 

A glass electrode pH meter consists of two electrodes—the reference electrode and the working electrode. The working electrode contains a thin layer of platinum metal that catalyses hydrogen ions from water molecules. This produces an electrical potential across the solution in the glass electrode thanks to an oxidation-reduction reaction.

Finally, an ion-selective pH meter measures the distribution of ions in an aqueous solution, making it highly dependent on the type of ions present. These instruments can also measure any ionic system with an exchangeable proton, including acids, bases, and buffers.

How pH Meters Work

pH stands for potential of hydrogen—a measure of the acidity or basicity of an aqueous (water-based) solution. pH meters, then, work to measure this property.

Most pH meters function by connecting to the solution and measuring the amount of electric current that passes through it when an electrode is immersed in the solution.

A pH probe, which is composed of two electrodes—one negatively charged, and one positively charged—will then convert this measured current into a readable voltage on the device’s display screen.

Common Industry Applications

pH meters are a common sight within a range of industries, including:

  • Agriculture, for measuring the pH levels in soil,
  • The food industry, for food quality control,
  • The swimming pool industry, for maintaining water safety,
  • Municipal water supplies, again for maintaining water safety,
  • The brewing industry, 
  • Experimentation within laboratories.

Let’s Summarise

To summarise, pH meters play a key role in industries such as manufacturing, agriculture, healthcare, the food industry, and many more. They’re essential for monitoring product quality and ensuring consumables remain safe for the community.

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