Vibronic Point Level Detection

Vibronic Point Level Detection

Vibronic point level detection uses vibrating elements (commonly tuning forks or rods) as point level switches in liquids and solids. The sensor vibrates at a characteristic frequency; when the process medium covers the element, vibration frequency and/or amplitude changes, and the device switches state. The result is a highly repeatable discrete signal for high/low alarming and interlocks across a broad range of media types.

A major advantage is reduced dependence on electrical properties such as conductivity or dielectric constant. Vibronic switches can perform reliably in many liquids regardless of composition changes, and they are commonly stable in the presence of bubbles, turbulence, or moderate foam. Many designs also incorporate self-monitoring behavior, enabling fault detection for wiring or sensor integrity issues - an important characteristic when used in protective functions.

Constraints are primarily mechanical and service-related. The sensor must contact the medium, so coating, crystallization, or heavy solids accumulation can affect switching behavior if the installation does not discourage buildup. For solids, the bulk density and flow characteristics must be sufficient to dampen the vibration in a detectable way, and abrasion should be considered for sharp or gritty materials. Mounting orientation and insertion depth are often critical to achieving clean wet/dry transitions.

Typical applications include overfill prevention (high-high switches), low-level pump protection (dry-run), and point detection in tanks containing chemicals, hydrocarbons, utilities, and hygienic fluids. In powders and granulates, vibronic switches are used for bin full/empty detection and material presence interlocks in feeders and hoppers. Their repeatability makes them common in standardized instrument specifications for point-level safeguarding.

Selection generally addresses hygienic vs. industrial mechanical design, materials/coatings for compatibility, required approvals (hazardous area, safety), and switching behavior (fail-safe high/low). Commissioning is usually simple compared with capacitance or ultrasonic point devices, but long-term reliability still benefits from intentional placement away from fill streams, impingement zones, and persistent buildup regions.

George E. Booth Co., an exclusive authorized representative of sales and service for Endress+Hauser.