What Is a Digital pH Meter?

Valerie Clark

A digital potential of hydrogen (pH) meter is an electronic gadget used to accurately measure and record the pH values of liquids. Measuring pH allows one to determine the acidity or alkalinity of a substance in a liquid state. The digital pH meter apparatus consists of a glass electrode attached to the end of a probe and connected to an electronic device with a digital display. When the pH of a substance is measured with the probe, the digital pH meter displays an accurate reading in pH units.

Without a pH meter, the acidity of a sample must be tested using chemical agents.
Without a pH meter, the acidity of a sample must be tested using chemical agents.

Digital pH meters work by emitting a tiny voltage through a glass electrode, which produces a value corresponding to the number of hydrogen atoms present in the solution being measured. A digital pH meter is similar to a voltmeter with the exception of displaying the recorded values in pH units rather than volts. One pH unit is equivalent to approximately 0.06 volts.

Acidic water will produce a pH reading of under 7.
Acidic water will produce a pH reading of under 7.

A buffer solution of a known pH level is used to calibrate the digital meter prior to use to ensure accurate readings. An alkaline buffer at pH 4 and an acidic buffer at pH 10 are most commonly used for a two-point calibration. In situations requiring increased accuracy, a neutral buffer at pH 7 also is used for a three-point calibration.

Using a digital pH meter is simple. It is important to rinse the probe in distilled or deionized water before and after each use. To record the pH level of a substance, the probe is carefully inserted into a liquid substance so the glass electrode is not damaged. The digital pH meter will instantly begin to display values. When the reading stabilizes, the measurement is complete and the probe can be removed and rinsed with distilled water.

Storage of a digital pH meter in an acidic buffer solution at pH 3 is recommended. Additionally, a monthly cleaning of the electrode and probe with hydrochloric acid (HCl) is recommended. The pH of the cleaning solution should be near 1.

Additional features and functions may be available on select digital pH meter models. Some of these options may include a portable, waterproof design and added temperature measurement ability. Special digital pH meters also are made for substances such as beer and food.

Digital measuring tools such as a pH meter are important for maintaining consistent and accurate recordings. When digital pH meters are not available, an alternative method for pH measurement exists. A small strip of paper with a colored dye that will indicate acidity and alkalinity can be used for basic acid-base measurements.

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