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Illustration of pH Meter and laboratory for article on how to use a pH Meter.
Published On: November 9th, 2021
If you remember those science experiments from school where you used litmus paper to test solutions, you probably know what pH is. In essence, it’s a common scale used to measure the acidity and basicity of a solution containing water as a solvent (aqueous). Without the presence of water, you cannot measure the pH of a substance.While the litmus paper experiment in school is cool, in a real-world setting, scientists use pH meters to measure the pH of a solution. Below, we explain what a pH meter is and how to use it.

What is a pH Meter and What Types are There?

A pH meter is an answer to the question, “what do you use to measure pH?”. While there are a variety of pH meters available for different purposes, most people will learn how to use a pH meter that’s one of the three types below:

  • Benchtop pH meters – Laboratories mostly use this type of pH meter to test samples/solutions that are brought on-site. These meters are heavier and have more customizations that allow for more precise results.
  • Portable/handheld pH meters – This type of pH meter is typically used in the field, and is light and small in size.
  • Pen pH meters – these are perfect for testing pH within test tubes and smaller containers. Pen pH meters are extremely portable and usually inexpensive, though they may not be as durable or accurate as benchtop or handheld pH meters.

Components of a pH Meter

Portable pH meters have two parts: the meter component, which displays readings and other info (and contains controls), and an electrode to dip into the solution which pH needs to be measured. Benchtop pH meters often additionally have an arm that holds the electrode and can be moved up and down into beakers and other lab containers. When pH meters are automated, this arm is often a robotic arm.

How to Use a pH Meter: First, Calibrate

Those learning how to use a pH meter are often told that they first need to calibrate the meter. So, why is it necessary to calibrate a pH meter before you use it? That’s because with use, the electrode of a pH meter tends to erode over time, and this causes the reading to become inaccurate. The calibration process is important to ensure that your pH meter is capturing the pH of a solution precisely despite some changes to the electrode.

pH meters are calibrated by placing the electrode into at least two standard buffer solutions with a known pH. Usually, one buffer solution would have a pH of 4.0, and the other solution would either be a pH 7.0 or 10.0. Once the electrode is placed into either of these solutions in calibration mode, the user would have the option to set the meter to the correct pH as per the buffer solution. This helps the meter show the correct reading even with incorrect or compromised data — due to electrode function decline.

How to Use a pH Meter: Operation Steps

Once the pH meter has been successfully calibrated, it will be ready to use for testing. First, the electrode should be washed with deionized water to cleanse it thoroughly and dried with scientific wipes to avoid dilution of the sample being tested. After this, place the electrode in the solution and take its reading. After use, pH meters should ideally be kept in a suitable storage solution. These are the necessary steps to ensure the most precise readings.

Laboratories that would like to take it a step further should invest in ph meter automation, integrated with other systems that complete a process. Need more info on how to use a pH meter seamlessly? Contact Hudson Robotics, and we can help.