A non-intrusive very high-frequency conductivity detector for continuous flow monitoring

A non-intrusive inductively-coupled conductance detector operating at 115 MHz is described. The flowing sample passes through a straight glass tube confined within the inductance coil of a parallel tuned high-Q circuit. Changes in Q caused by the resistive component of the sample are measured. Potassium chloride in water can be monitored down to 2 ppm with a linear response over three orders of magnitude of concentration.