Which device is used to measure level in a conductive fluid?

• A. A conductivity probe
• B. A pressure transducer
• C. A thermocouple
• D. A level switch

Answer: (A)

When a liquid conducts electricity, you can detect its level by sensing electrical conductivity between electrodes immersed in the fluid. A conductivity probe uses electrodes; when the liquid surrounds the electrodes, ions carry current and the probe reads a measurable conductivity, signaling that liquid is present up to that height. This method provides a direct indication of liquid level for conductive fluids, and it tends to be more straightforward for this specific property than methods that rely on pressure or temperature. A pressure transducer measures hydrostatic pressure to infer level, which works in many liquids but doesn’t exploit conductivity and can be influenced by density and temperature changes. A thermocouple only measures temperature, not level. A level switch gives a binary indication at a fixed point rather than a continuous level measurement.