Vibrating Fork Level Switch

The vibrating fork is the point level switch that needs no calibration and no knowledge of the product. A piezoelectric drive vibrates the fork at its resonant frequency in air; when liquid covers the tines the frequency drops, and the electronics switch. Density, conductivity, dielectric constant, foam, bubbles, turbulence and light coating have no effect, and the switch tests itself continuously for corrosion, damage and drive failure.

Switches are available with a short fork for direct mounting or an extension tube or cable to 6 m for insertion from the top, with threaded or flanged connections at process conditions to 160 bar and −196 to +450 °C. Wetted parts are 316L stainless steel or Hastelloy, with enamel, PFA or ECTFE coatings for aggressive media and a polished finish for hygienic service. Outputs cover every control system: relay, SPDT or DPDT, PNP or NPN transistor, NAMUR, 8/16 mA two-wire and IO-Link. Weather covers, display modules, locking fittings and plug connectors complete the range.

Certified versions are available for overfill prevention and safety instrumented systems, with a test function that proves the switch without raising the level.

Applications are overfill protection, dry-run protection for pumps, pipeline detection, steam boilers and cryogenic tanks in chemical, power, food, water, pharmaceutical, oil and gas and marine industries.