Tuning fork

A tuning fork shaped sensor is excited at its resonant frequency.

Capacitance

A capacitance probe can be compared to an electrical capacitor.

Conductivity

The resistance between two measuring electrodes changes due to the presence or absence of a product.

Radiometric

A gamma ray source, consisting of a Cesium or Cobalt isotope, emits radiation that is attenuated as it passes through materials.