Why ultrasound?
…for flow measurement (e.g., gas flow measurement and wind measurement).
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Ultrasonic vs. calorimetric sensor technology
Calorimetric sensors use heat transfer to determine the flow velocity of gases. A heated sensor element is cooled by the gas flow. The greater the cooling, the higher the flow velocity. Typical applications include monitoring gas flow in process plants, leak detection, and air flow measurement in HVAC systems (heating, ventilation, and air conditioning).
SECO thinks:
Compared to calorimetric sensors, ultrasound is…
Regardless of the gas composition
Calorimetric measurement is influenced by specific thermal conductivity and gas composition. Ultrasound operates independently of these factors.
More responsive
Calorimetric measurements require a certain amount of time for the temperature difference to stabilize. Ultrasound reacts immediately to changes in volume flow.
More accurate with large flow rates
Ultrasound is also suitable for large pipe diameters and volume flows. Calorimetric measurement is more suitable for small flow rates.
Suitable for bidirectional measurements
Calorimetric sensors are generally designed to measure in one direction. Ultrasound can detect and measure the direction of flow.
Ultrasonic vs. differential pressure sensors
Differential pressure sensors use the pressure difference between two points in the flow profile to calculate the velocity and volume flow of gases. Typical applications include flow measurement in pipelines, monitoring ventilation and air conditioning systems, and process control in industry. Differential pressure sensors use measuring principles such as orifices, venturi nozzles, or Pitot tubes.
SECO thinks:
Compared to differential pressure sensors, ultrasound is…
A non-contact measuring method
Ultrasound does not cause any additional flow resistance. Blinds or valves on the differential pressure sensors can cause pressure losses.
More accurate measurements under variable conditions
Differential pressure sensors are highly dependent on density and usually require complex compensation. Ultrasound is less sensitive.
Suitable for large pipe diameters
Ultrasound can also be used in very large pipes without mechanical intervention. Differential pressure requires large and expensive installations.
Suitable for bidirectional measurements
Ultrasound detects the flow direction and measures in both directions. Differential pressure sensors are usually designed for one direction only.
Ultrasound vs. vortex sensor technology
Vortex sensors use the formation of vortices behind an obstruction in the gas flow to determine the flow velocity. The frequency of the vortices is proportional to the flow velocity. Typical applications include flow measurement in process lines, monitoring of gas and steam systems, and energy and media billing. Vortex sensors operate according to the Kármán vortex street principle.
SECO thinks:
Compared to vortex sensors, ultrasound is…
Suitable for low flow rates
Ultrasound measures reliably even at very low flow rates, while vortex sensors require a minimum velocity to generate vortices.
Independent of flow profile
Ultrasound is less sensitive to turbulent flows. Vortex sensors can provide erroneous signals under such conditions.
Suitable for bidirectional measurements
Ultrasound detects the flow direction and measures in both directions. Vortex sensors are usually designed for one direction only.
Maintenance-free
Ultrasound operates without moving parts. Vortex sensors have a disruptive element in the medium that is exposed to contamination and deposits.
Ultrasonic vs. Coriolis Sensors
Coriolis sensors measure the mass flow of gases using the Coriolis force, which acts on oscillating measuring tubes when the medium flows through them. Typical applications include high-precision flow measurement in the process industry, gas metering, and energy billing. Coriolis sensors work with direct mass-based measurements.
SECO thinks:
Compared to Coriolis sensors, ultrasound is…
More cost-effective and easier to install
Ultrasonic sensors can often be installed without opening the pipeline. Coriolis sensors are expensive and require complex installations.
Suitable for large pipe diameters
Ultrasound can be used without any problems on very large pipes. Coriolis sensors are limited in size and are hardly practical for large diameters.
Non-invasive on the flow cross-section
Ultrasound operates without contact and does not cause any pressure loss. Coriolis sensors require measuring tubes that alter the flow cross-section.
More space-saving and lighter
Ultrasonic systems are compact and lightweight. Coriolis sensors are bulky and heavy, which can make installation difficult and lead to higher costs.
Ultrasound vs. Laser Doppler anemometry
Laser Doppler anemometers measure the flow velocity of gases without contact by evaluating the Doppler shift of laser light scattered by particles in the gas. Typical applications include precise flow analyses in laboratories, the validation of flow models, and special measurements in research. Laser Doppler anemometers work with high-resolution laser optics.
SECO thinks:
Compared to Laser Doppler anemometers, ultrasound is…
Easy to install and integrate
Ultrasonic sensors can be mounted directly on pipes or used as clamp-on systems. Laser Doppler anemometers often require special measurement setups.
Robust for industrial use
Ultrasound is resistant to dust, dirt, and difficult environmental conditions. Laser Doppler systems are sensitive to contamination and require stable optical conditions.
Independent of particles in the gas
Ultrasound measures independently of particles in the medium. Laser Doppler anemometers require scattering particles in order to detect the Doppler shift.
More cost-effective
Ultrasound solutions are significantly more cost-effective. Laser Doppler systems are complex, expensive, and usually only economical for laboratory or special applications.
Sensor comparison: Why ultrasonic sensors are the best choice for flow measurement
Sensors for measuring gas flow are crucial for process control, energy billing, and safety in industrial applications. They measure flow velocity or volume flow and enable precise control. The most important technologies include calorimetric, differential pressure, vortex, Coriolis, laser Doppler, and ultrasonic sensors. Each technology has specific characteristics that determine its areas of application.
Calorimetric sensors work with heat transfer: a heated element is cooled by the gas flow; the greater the cooling, the higher the flow velocity. They are compact and simple, but sensitive to gas composition and temperature.
Differential pressure sensors measure the pressure difference between two points in the flow profile and use this to calculate the velocity. They are robust and proven, but cause pressure losses and require compensation for temperature and density.
Vortex sensors utilize the formation of vortices behind an obstructing body. The vortex frequency is proportional to the flow velocity. They are reliable for medium to large flow rates, but require a minimum velocity and are susceptible to contamination.
Coriolis sensors measure mass flow directly via the Coriolis force in oscillating measuring tubes. They offer maximum accuracy, but are expensive, heavy, and impractical for large pipe diameters.
Laser Doppler anemometers detect the Doppler shift of laser light scattered by particles in the gas. They provide extremely accurate results, but are complex, costly, and limited to laboratory applications.
Ultrasonic sensors emit sound waves and measure the difference in transit time between signals in and against the direction of flow (time-of-flight principle). They are non-contact, cause no pressure loss, operate independently of gas composition, and are suitable for large pipe diameters. Their robustness and versatility make ultrasonic sensors the preferred solution for many industrial applications.