Difference Between pH Meter and Potentiometer

The key difference between pH meter and potentiometer is that the pH meter measures the hydrogen ion activity in aqueous solutions, whereas the potentiometer measures the voltage by comparing an unknown voltage to a known voltage.

pH meter is often used in chemical analysis for the measurement of pH of water-based solutions. However, it is a type of potentiometer because it measures the potential difference between the pH electrode and a reference electrode. Generally, potentiometers have a wide variety of uses in the electric industry other than measuring the pH of a solution.

CONTENTS

1. Overview and Key Difference
2. What is a pH Meter 
3. What is a Potentiometer
4. Side by Side Comparison – pH Meter vs Potentiometer in Tabular Form
5. Summary

What is a pH Meter?

pH meter is a type of potentiometer we can use to measure the hydrogen ion activity in aqueous solutions. The instrument can indicate the acidity and basicity of solutions as a pH value. The higher the pH value, the more the alkaline is the solution. The lower the pH value, the more acidic the solution is. Besides, it is a type of potentiometer because it measures the potential difference between the pH electrode and a reference electrode. However, this difference in electric potential relates to the pH of the solution.

When considering the principle behind the pH meter, it measures the voltage between two electrodes and displays the result as a pH value. The meter contains a simple electronic amplifier and two electrodes for this purpose. Moreover, it has a display that is calibrated with pH units and a probe, which contains the pH electrode. To measure the pH, we need to immerse the probe into the test solution.

The electrodes in this instrument are rod-like structures. Usually, manufacturers make these probes using glass. The probe contains a bulb as the sensor at the terminal. The glass electrode specifically contains a glass bulb that is sensitive to the hydrogen ion concentration. When we immerse the probe in the test solution, the hydrogen ions in the solution are exchanged with the positively charged ions in the glass bulb. It creates an electrochemical potential across the glass bulb. Then, the electronic amplifier can detect this potential difference and converts it into pH units.

Furthermore, we commonly use pH meters for the determination of acidity and alkalinity of water, i.e. drinking water. Moreover, it is important in laboratory analysis. Besides, it is also important in soil pH measurement for agricultural purposes.

What is Potentiometer?

A potentiometer is an instrument we use to measure voltages. It measures the voltage by comparing a known voltage with an unknown voltage. If we use a highly sensitive instrument, then we have to draw a little current through the source having the unknown voltage. The known voltage is “the reference voltage”. A potentiometer can give very accurate results if we use an accurately calibrated voltage diver.

In the principle of operation, the potential dropped across a segment of wire (which has a uniform cross-section and carries a constant current) is directly proportional to the length of the wire. The potentiometer is a simple device, and we use it to measure electric potentials.

What is the Difference Between pH Meter and Potentiometer?

The key difference between pH meter and potentiometer is that the pH meter measures hydrogen ion activity in aqueous solutions, whereas the potentiometer measures the voltage by comparing an unknown voltage to a known voltage. Moreover, the pH meter measures the voltage between two electrodes (indicator and reference electrodes) and display the result as a pH value. However, the principle of a potentiometer is that the potential dropped across a segment of wire (which has a uniform cross-section and carries a constant current) is directly proportional to the length of the wire. So, this is the difference between pH meter and potentiometer in terms of the principle behind their function.

The below infographic details more information related to the difference between pH meter and potentiometer.

Summary – pH Meter vs Potentiometer

In summary, the pH meter is a type of potentiometer. However, the key difference between pH meter and potentiometer is that the pH meter measures the hydrogen ion activity in aqueous solutions, whereas the potentiometer measures the voltage by comparing an unknown voltage to a known voltage.

Reference:

1. “PH Meter.” Wikipedia, Wikimedia Foundation, 3 June 2019, Available here.

Image Courtesy:

1. “PH Meter” By Datamax – Own work (Public Domain) via Commons Wikimedia
2. “Moog Sub 37 (2014-) potentiometer are plastic shaft, but are bolted to the panel” By Pete Brown from Gambrills, MD, USA – Sub 37 potentiometer (CC BY 2.0) via Commons Wikimedia