The conductivity sensor measures the electrical conductivity in a solution, which is the solution's ability to conduct an electric current and is directly related to the concentration of ions. These sensors are widely used in water quality monitoring, industrial process control, and environmental monitoring.

Common Types of Conductivity Sensors:

Two-electrode (Contacting) Sensors: These sensors feature two electrodes that directly contact the solution, making them suitable for low to moderate conductivity ranges.

Four-electrode Sensors: These sensors utilize four electrodes to deliver more precise measurements across a wider range of conductivities and minimize polarization effects.

Inductive (Toroidal) Sensors: These sensors employ a magnetic field to induce a current in the solution, making them ideal for high conductivity measurements and less prone to fouling and coating.

Four-electrode Conductivity Meter Principle

The conductivity sensor operates based on the electrical conductivity of a solution, which indicates its capacity to conduct an electric current. Here's a simplified explanation of the working principle:

• Electrode Configuration:

  Four Electrodes: A four-electrode sensor consists of two current electrodes and two voltage electrodes. The current electrodes are used to apply an alternating current, and the voltage electrodes are used to measure the voltage drop.

  Electrode Arrangement: The current electrodes are usually located at the ends of the sensor, while the voltage electrodes are located in the middle, close to the solution being measured. This configuration reduces electrode polarization effects and improves the accuracy of the measurement.

   

• AC Current:

  The sensor applies a steady alternating current (AC) through the current electrodes, causing the current to flow through the solution. This AC current helps prevent the accumulation of ions on the electrode surface, thereby avoiding polarization effects.

   

• Voltage Measurement:

  When an AC current flows through the solution, the voltage electrodes measure the voltage drop that the current produces in the solution. Since the voltage electrodes do not directly pass current, they are not affected by polarization effects, which makes the voltage measurement more accurate and stable.

  
  

• Conductivity calculation:

  The sensor calculates the conductivity of the solution based on the measured voltage drop and the known current value. The calculation formula for conductivity (κ) is: K=I/V*K

  I is the applied current, V is the measured voltage drop, and K is the cell constant of the sensor (determined by the geometry of the electrodes).

  
  

• Temperature compensation:

  Conductivity is temperature dependent, and changes in solution temperature affect the mobility of ions and thus conductivity. Therefore, many four-electrode conductivity sensors have built-in automatic temperature compensation (ATC) functions to ensure accurate measurements at different temperatures.

Application of Electrical Conductivity Meter:

• Water Treatment: Monitoring the quality of drinking water, wastewater, and industrial water.

• Chemical Industry: Controlling the concentration of chemical solutions.

• Environmental Monitoring: Assessing the health of natural water bodies.

• Food and Beverage Industry: Ensuring product quality and consistency.

Conductivity sensors are essential tools in various industries for monitoring and maintaining the quality of solutions and processes.