Radar vs Ultrasonic Liquid Level Transmitters: Which Technology Fits Your Application Best?

Choosing a reliable, high-performance liquid level transmitter is critical for efficient tank monitoring in various industries—from water treatment and petrochemicals to food processing and industrial waste management. Among non-contact sensor technologies, radar and ultrasonic level transmitters dominate due to their safety, versatility, and performance.

Both operate on time-of-flight (ToF) principles, where the transmitter emits a signal and measures the time it takes to bounce off the liquid surface and return. But despite this shared core principle, radar and ultrasonic sensors differ significantly in their operation, performance, environmental resilience, and application suitability.

This article provides a detailed comparison between radar and ultrasonic level transmitters to help you choose the right sensor for your specific needs.

1. How Ultrasonic Level Transmitters Work

Ultrasonic level sensors transmit high-frequency sound waves (typically 20–75 kHz) toward the surface of a liquid. These waves reflect off the surface and return to the sensor. The time delay between sending and receiving the signal is used to calculate the distance to the liquid surface and, consequently, the level.

Advantages:

• Cost-effective and widely available

• Simple design and easier to install

• Suitable for basic level monitoring of clean liquids

Limitations:

• Highly sensitive to environmental conditions like:

• Temperature

• Humidity

• Dust

• Vapor or gas layers

• Poor performance with foam or turbulent surfaces

• Wider blind zone (~300–500 mm) compared to radar

  
  

  
  

2. How Radar Level Transmitters Work

Radar transmitters operate using electromagnetic waves in the microwave spectrum (typically 6 GHz, 26 GHz, or 80 GHz). These signals are reflected back from the liquid surface to the sensor, where the time-of-flight is used to determine the level.

There are two main types of radar transmitters:

• Non-contact radar (FMCW or pulse radar)

• Guided wave radar (GWR), which uses a probe inserted into the tank

Advantages:

• Immune to changes in temperature, pressure, vapor, and dust

• Higher accuracy (up to ±1 mm in some models)

• Can detect through foam and deal with turbulent or viscous liquids

• Smaller blind zone (~50–100 mm), ideal for small tanks

• Suitable for high-pressure, high-temperature environments

Limitations:

• Historically more expensive (though cost gaps are narrowing)

• May require more advanced configuration or technician setup

• May need explosion-proof certification in hazardous zones

3. Side-by-Side Performance Comparison

4. Application Scenarios: Where Each Excels

Best Use Cases for Ultrasonic Level Sensors:

• Municipal water tanks and wastewater treatment

• Irrigation systems and environmental monitoring

• Non-hazardous, low-pressure tanks with consistent conditions

Best Use Cases for Radar Level Sensors:

• Petrochemical and oil & gas tanks (including pressurized tanks)

• Food and beverage processing with foamy, sticky, or viscous fluids

• High-temperature and high-pressure environments

• Tanks with vapor, dust, or condensation interference

• Tall silos or outdoor storage units with variable weather

5. Installation and Maintenance Considerations

Ultrasonic Transmitters:

• Easy to install and calibrate

• Must be placed where there are no obstructions or structural interference

• Periodic cleaning required due to potential buildup on transducer

Radar Transmitters:

• Slightly more complex installation

• Typically maintenance-free, especially non-contact models

• Can be mounted on metallic or plastic tanks without special preparation

6. Output Signal and Communication Options

Both radar and ultrasonic transmitters support a wide range of industrial communication protocols, including:

• 4–20 mA

• HART

• Modbus

• Profibus

• RS-485

• LoRa/NB-IoT (in wireless models)

Radar systems are more likely to support advanced diagnostics, remote monitoring, and integration with SCADA/PLC systems, making them better suited for Industry 4.0 applications.

7. Future Trends and Technology Evolution

• 80GHz radar is rapidly replacing older radar models due to improved beam focusing, smaller antennas, and greater range.

• Artificial intelligence (AI) and self-calibrating sensors are emerging for both radar and ultrasonic to handle complex or changing conditions.

• Wireless radar level sensors with battery-powered operation are enabling remote monitoring in hard-to-access areas.

• The cost of radar transmitters has dropped significantly, making them a competitive alternative even in budget-conscious applications.

8. Conclusion: Which Should You Choose?

If your application involves clean liquids in stable environments with limited budgets, ultrasonic sensors remain a reliable and affordable choice.

However, for critical applications, including those with challenging environmental conditions (foam, vapors, temperature fluctuations), or where high precision is required, radar level transmitters provide superior performance and reliability.

In many modern installations, both technologies can be used complementarily—ultrasonic sensors for basic monitoring, and radar for mission-critical operations.

Need Help Selecting the Right Sensor?

Contact Beijing Gallop group technical team for personalized guidance on choosing between radar and ultrasonic level measurement systems. We'll help you assess your tank design, liquid type, and environmental conditions to ensure optimal performance.