Ultrasonic Level Measurement

Ultrasonic Level Measurement

Ultrasonic level measurement is a continuous, non-contact method for measuring level in liquids and many bulk solids using acoustic time-of-flight. A transducer emits ultrasonic pulses and measures the echo from the surface; distance is converted to level using known vessel geometry. It is often applied as a cost-effective solution when vapor space conditions are suitable for reliable sound propagation.

The measuring principle is time-of-flight: the sensor transmits an ultrasonic pulse, the media surface reflects it, and the sensor detects the return. The elapsed time is proportional to distance traveled; with tank dimensions known, level is calculated. Many ultrasonic sensors include features that reduce build-up sensitivity, including a diaphragm motion that can provide a self-cleaning effect in certain services.

Benefits include maintenance-free operation (no wetted moving parts), relatively simple planning and installation, and the ability to commission without filling or emptying the vessel in many cases. Ultrasonic measurement is also generally independent of dielectric constant and can be effective across a variety of fluids, pastes, sludges, and solids - provided the acoustic path remains stable.

Typical applications include water and wastewater tanks, sumps, and channels; chemical storage where moderate vapors are present; and solids bins for powders or granulates when dust loading and range are within the device’s capability. It is also used for abrasive or aggressive media since the sensor does not contact the product, making it useful in outdoor or rough ambient environments.

Application engineering should address factors that influence sound velocity and echo quality: temperature gradients, heavy vapors, foam, turbulence, and dust can all degrade signal strength. Mounting should avoid strong internal reflections from ladders, braces, or inflow streams, and dead band near the sensor must be considered for high-level alarms. When vapor space composition varies significantly, compensation and validation should be included to maintain accuracy.

Forberg Smith, an exclusive authorized representative of sales and service for Endress+Hauser.