Which instrument measures electrical conductivity?

• A. Water level indicator
• B. pH/redox meters
• C. EC meters
• D. Gas detector

Answer: (C)

Electrical conductivity is measured with an EC meter. This instrument assesses how readily a solution conducts electricity, which increases with the concentration of ions in the liquid. An EC meter uses two (or four) electrodes to pass a small current through the solution and then measures the resulting conductance, giving a reading in units such as μS/cm or mS/cm. Temperature compensation is often built in because conductivity changes with temperature, so readings can be standardized to a reference temperature like 25°C. This measurement is a quick way to gauge ion content, salinity, or total dissolved solids in water samples, which is why EC meters are commonly used in water quality work. The other instruments serve different purposes: a water level indicator measures height, a pH/redox meter gauges hydrogen ion activity or oxidation-reduction potential, and a gas detector monitors the presence of gases.