Conductivity Probe
A conductivity probe is a solid-state sensor that measures the electrical conductivity of a liquid by quantifying current flow between two or more electrodes (graphite, platinum, or metal) in response to an applied voltage. This directly indicates the concentration of ions or Total Dissolved Solids (TDS), enabling precise monitoring of water purity and chemical concentration in industrial processes.
In manufacturing and asset reliability, conductivity probes are deployed for liquid level control, replacing mechanical floats to automate pumps and detect contamination in cooling loops. They monitor water purity in reverse osmosis systems by detecting when a conductive fluid completes a circuit between a Common and an Active electrode, triggering a relay state change below a resistance threshold (e.g., <50 kΩ). This enables real-time process control, preventing equipment damage from poor water quality and ensuring efficient operation of critical systems like boilers and heat exchangers.
How does the cell constant (K) affect conductivity calculation (σ)?
Conductivity is calculated as σ = I / (V × K), where I is current and V is voltage; the cell constant represents the geometric ratio of electrode distance to area, and errors in K (due to physical damage or corrosion) directly scale measurement errors.
Why are inductive (toroidal) probes preferred for harsh chemical environments?
They use electromagnetic induction rather than direct electrical contact, eliminating electrode contamination and polarization issues, making them ideal for aggressive samples where contacting probes would degrade rapidly.
What is the distinction between conductance (G) and conductivity (σ)?
The probe measures conductance (reciprocal of resistance, G = 1/R), while conductivity is the normalized property of the solution (σ = G × K), accounting for the probe's geometry to provide a material-specific value in µS/cm or mS/cm.