What is the Difference Between pH Meter and Conductivity Meter

The key difference between pH meter and conductivity meter is that the pH meter measures the activity of hydrogen ions in aqueous solutions, whereas the conductivity meter measures voltage through the comparison of an unknown voltage with a known voltage.

A pH meter can be described as a type of potentiometer we can use to measure the hydrogen ion activity in aqueous solutions. A conductivity meter or potentiometer can be described as an instrument we use to measure voltages.

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

What is a pH Meter?

A pH meter is a type of potentiometer we can use to measure the hydrogen ion activity in aqueous solutions. The pH meter can indicate the acidity and basicity of solutions as a pH value. In this measurement, the higher the pH value, the more alkaline the solution is. On the other hand, the lower the pH value, the more acidic the solution is. Moreover, a pH meter 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.

Typically, 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 convert it into pH units.

What is a Conductivity Meter?

A conductivity meter or 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 Conductivity Meter?

The key difference between pH meter and conductivity meter is that the pH meter measures the activity of hydrogen ions in aqueous solutions whereas the conductivity meter measures the voltage through the comparison of an unknown voltage with a known voltage.

The below infographic presents the differences between pH meter and conductivity meter in tabular form for side by side comparison.

Summary – pH Meter vs Conductivity Meter

A pH meter is a type of potentiometer we can use to measure the hydrogen ion activity in aqueous solutions. A conductivity meter or potentiometer is an instrument we use to measure voltages. The key difference between pH meter and conductivity meter is that a pH meter measures the activity of hydrogen ions in aqueous solutions, whereas a conductivity meter measures the voltage through the comparison of an unknown voltage with a known voltage.

Reference:

1. “Conductivity /Conductivity Meter.” MRCLAB.

Image Courtesy:

1. “Soil pH meter” By Gihan Jayaweera – At Open University of Sri lanka (CC BY-SA 3.0) via Commons Wikimedia
2. “Electrical conductivity meter” By Nmnogueira at English Wikipedia (CC BY-SA 2.5) via Commons Wikimedia