Ultrasonic Level Sensors: Reliable Non-Contact Measurement

The cost-effective standard for water, wastewater, and chemical tanks. Accurate, maintenance-free liquid level monitoring for industrial and municipal applications.

Ultrasonic technology remains the most efficient solution for non-contact level measurement in clean and wastewater environments. By using high-frequency sound waves, Longvista sensors provide precise readings without ever touching the medium—eliminating corrosion, buildup, and contamination.

Whether you need a wireless IoT solution (WUS10) for remote reservoirs, an explosion-proof sensor (UL30) for fuel, or a long-range transmitter (UL20) reaching up to 60 meters, our portfolio is engineered for stability in real-world conditions.

  • Non-Contact Reliability: Ideal for aggressive acids or hygienic food-grade applications.

  • Built-in Intelligence: Automatic temperature compensation and false-echo filtering come standard.

  • Simple Integration: Plug-and-play setup with 4-20mA, RS485 Modbus, or LoRaWAN connectivity.

Quick Selection Guide: Find Your Model

Use this matrix to identify the right sensor for your specific technical constraint:

Model Primary Application Key Strength Max Range
UL105 General Industrial High Accuracy (±0.2%) 15m
UL20 Deep Silos / Large Tanks Extended Range Up to 60m
UL40 Open Channels / Weirs Level-to-Flow Calculation 15m
UL30 Fuel & Chemical Tanks Explosion-Proof (Ex) 10m
WUS10 Remote Monitoring Wireless (NB-IoT/LoRa) 10m
UL106 Industrial Sumps Harsh Environment Robustness 10m
UL101 Compact Tanks Small Dead Zone / Low Cost 5m

Engineering Essentials – Accuracy & Environment

To achieve stable measurements, an ultrasonic sensor must account for changes in the air through which the sound travels. Unlike radar, ultrasonic waves are mechanical and depend on the medium (air/gas).

1. Automatic Temperature Compensation

The speed of sound changes by approximately 0.17% per degree Celsius. In an outdoor tank where temperatures fluctuate from -10°C at night to +30°C in the sun, this can cause a 7% measurement error.

  • The Longvista Solution: Models like the UL105 and UL20 include integrated temperature sensors that automatically adjust the distance calculation in real-time, maintaining precision regardless of weather changes.

2. Mastering the “Dead Zone” (Blind Zone)

The Dead Zone is the area directly beneath the sensor face where the transducer cannot “listen” because it is still vibrating from the transmission.

  • Compact Tanks: For small vessels, choose the UL101 or UL103, which feature optimized transducers with shorter dead zones (as low as 0.2m).

  • Deep Reservoirs: Long-range sensors like the UL20 have larger dead zones (up to 1.0m) but provide the acoustic power needed to reach 60 meters.

  • Pro Tip: Always mount the sensor so the maximum possible liquid level remains below the dead zone limit to avoid signal “lock-up.”

Application-Specific Selection

Matching the sensor to the environment is critical for preventing “signal loss” errors.

Open Channels & Flow Monitoring

For weirs, flumes, and irrigation canals, the UL40 is specifically programmed for Level-to-Flow conversion. It compensates for environmental wind and surface ripples, providing a stable volumetric flow rate instead of just a distance measurement.

Harsh & Corrosive Environments

In wastewater treatment or chemical processing, acidic vapors can degrade standard sensors.

  • UL106: Features a reinforced housing and specialized transducer face resistant to the humidity and corrosive gases found in industrial sumps.

  • UL30: Designed with an Explosion-Proof (Ex) rating for hazardous zones where fuel, oil, or solvent vapors are present.

Wireless & Remote IoT (IIoT)

For remote sites where cabling is impossible or too expensive, the WUS10 utilizes LoRaWAN, NB-IoT, or 4G connectivity. This model is ideal for smart city water management and flood early-warning systems.

Surface Conditions – When to use Ultrasonic

Surface Condition Ultrasonic Performance Recommendation
Clean Water Excellent UL105 / UL101
Light Ripples Good UL20 / UL106
Heavy Foam Poor (Absorbs Sound) Switch to Radar (MQ Series)
Heavy Steam Variable Use Waveguide or Radar

Installation Best Practices for Maximum Reliability

Even a high-accuracy sensor like the UL105 will provide unstable readings if poorly positioned. Follow these engineering guidelines for a “set and forget” installation:

  • Vertical Alignment: The transducer must be perfectly perpendicular to the liquid surface. A tilt of just 3° can cause the echo to bounce away from the receiver, leading to “Signal Lost” errors.

  • Avoiding “Obstruction Echoes”: Do not install the sensor near the tank wall or close to internal ladders, pipes, or agitators. Ultrasonic waves spread in a cone (typically 8–12°); ensure this cone is clear of obstructions.

  • The 10% Rule: To avoid the Dead Zone, always mount the sensor such that the highest possible liquid level is at least 10% further away than the sensor’s specified minimum blanking distance.

  • Stilling Wells for Turbulence: If the liquid surface is agitated by a pump or mixer, install the sensor inside a stilling well (a vertical pipe). This creates a calm surface for the sound waves to hit.

FAQ – Solving Common Ultrasonic Challenges

Q: Can I use an ultrasonic sensor for solids or powders?

A: While possible, it is challenging. Solids (like grain or sand) absorb sound waves and often sit at an angle, reflecting the echo away. For solids, we strongly recommend our MQ8 Radar series.

Q: How do I handle heavy foam in a wastewater tank?

A: Thick foam acts like an acoustic sponge, absorbing the ultrasonic pulse. If you have more than 2cm of foam, consider using a submersible pressure transducer or a radar sensor.

Q: Does wind affect outdoor measurements (e.g., in a canal)?

A: Strong wind can “blow” the sound wave away. For outdoor hydrology, the UL40 is designed with specific filtering to handle environmental disturbances, but a protective shield is always recommended.

Q: Can the WUS10 wireless sensor work inside a metal tank?

A: If the tank is completely sealed metal, the wireless signal (LoRa/NB-IoT) cannot get out. You must use an external antenna or mount the sensor such that the antenna has a clear line of sight to the gateway.

At-a-Glance Technology Comparison

Feature Ultrasonic (UL Series) Radar (MQ Series) Submersible (WUS Series)
Primary Benefit Cost-Effective / Non-Contact All-Weather / High Precision Deep Wells / Heavy Foam
Surface Sensitivity Sensitive to Foam/Vapor Immune to Foam/Vapor Measurement from Bottom
Complexity Simple Plug-and-Play Advanced Configuration Physical Installation Required
Price Point Low to Medium Medium to High Low to Medium

Reliable Level Control Starts Here

Whether it is a simple water tank or a complex industrial chemical process, the Longvista UL Series offers a proven, maintenance-free solution.

Ready to find your solution?

[Get a Custom Quote] – Tell us your tank height and medium; we’ll do the rest.

Ultrasonic level sensors are among the most versatile non-contact solutions in our level measurement portfolio, offering reliable and precise readings for water, chemicals, and industrial tanks—without ever touching the liquid. Their durability, ease of installation, and broad measurement ranges make them ideal for a wide variety of applications.

If you need alternative non-contact technologies, explore our Radar Level Sensors, which provide excellent performance in challenging conditions such as foam, vapors, or turbulence.
For applications requiring direct hydrostatic measurement, you can also consider our Submersible Level Sensors.

To complement your level monitoring system, we also offer Pressure Sensors and Flow Meters designed for hydraulic, environmental, and industrial processes.

Contact us for technical support or to receive a personalized quotation for our ultrasonic level measurement solutions.

MENU