4 Advice to Choose a wireless radar level transmitter

Chamber Construction of an External Cage Float Level Switch

In this blog post, Bob Botwinski, Sr. Global Product Manager, discusses how guided wave radar (GWR) and non-contact radar (NCR) can work together to provide reliable level measurement.

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The Best Applications For Each Technology

Due to the similarity between GWR and NCR with respect to both performance and capability, there will obviously be some overlap in the application set. Experience, comfort level, and plant-specific standards may dictate a user’s decision as which to use for any given application. However, we all know that “force-fitting” any technology to an application can result in post-installation issues. Therefore, there are some basic application questions that, when considered for a specific application, will quickly guide a user to the proper RADAR technology.

Three basic parameters, considered in this order, can help a user determine the best technology for RADAR level measurement applications:

1. Measurement Range

Since GWR requires the probe to be as long as the measurement range required, NCR is typically more suitable for large storage tank applications with slow moving levels. Shorter range, quicker moving process control applications, such as those in side-mounted chambers, are typically better suited with GWR.

 

2. Process Conditions (Temperature and Pressure)

Some GWR products have probes that can accommodate maximum temperatures up to 850F (450C) and maximum pressures up to psi (430bar). Some NCR antennas also have a maximum operating temperature of 850F (450C), but are limited in a maximum pressure rating of psi (160 bar). Therefore, GWR should be considered for those more difficult high temperature, high pressure applications.

3. Dielectric Constant of the Process Medium

With both GWR and NCR, the dielectric constant (ε) of the process medium dictates the size (amplitude) of the reflection from the surface of the material. High dielectric media like water (ε = 80) produce large reflections that are easily detected by the transmitter. On the other hand, low dielectric hydrocarbons (ε = 1.7 -3) result in low amplitude signals that may be difficult to detect reliably, especially with other adverse conditions like foaming and turbulence.

With the high frequency GWR signal being focused and transmitted down a waveguide, very little energy is lost as the signal travels down the probe. On the other hand, significant signal attenuation can occur with NCR devices in some applications. Being more efficient, GWR is, in general, the preferred technology for low dielectric applications (ε< ~ 2).

It must be stressed again that there can be other, perhaps non-technical, reasons one may choose the technology not meeting the criteria above. However, these three parameters, when considered either separately or together, are a good start in guiding the user to the most robust and reliable solution.

For more information, we have created a Radar Solutions brochure where you can learn more about our radar level measurement technologies.

Introduction

Radar level transmitters are non-contact, high-precision instruments widely used in industries like oil & gas, chemical processing, power generation, and food & beverage. Compared to traditional float-type or ultrasonic level sensors, radar transmitters offer superior interference resistance, adaptability to harsh environments, and low maintenance costs. This article explores their working principle, key advantages, applications, and selection criteria to help users choose the optimal solution.

1. How Radar Level Transmitters Work

Radar level transmitters operate based on microwave time-of-flight (ToF) measurement:

1. Signal Transmission: The antenna emits high-frequency electromagnetic waves (typically 6GHz, 26GHz, or 80GHz).

2. Reflection & Reception: Waves reflect off the liquid surface and return to the sensor.

3. Distance Calculation: The transmitter calculates liquid level by measuring the time delay between emission and reception, combined with the speed of light.

Key Advantages:

• Unaffected by density, temperature, or pressure – Ideal for corrosive, viscous, or high-temperature liquids.

• Non-contact measurement – Eliminates mechanical wear, ensuring long-term reliability.

2. Types of Radar Level Transmitters

(1) Pulsed Radar (Non-Contact)

• Frequency: 6GHz / 26GHz

• Features: Cost-effective, suitable for general liquids (water, oils, chemicals).

• Applications: Storage tanks, process vessels, wastewater treatment.

(2) FMCW Radar (Frequency-Modulated Continuous Wave)

• Frequency: 80GHz

• Features: Ultra-high accuracy (±1mm), excellent interference immunity for foam/steam.

• Applications: Food-grade tanks, pharmaceutical processing, precision control.

(3) Guided Wave Radar (Contact Type)

• Principle: Uses a probe to guide microwaves, ideal for low-dielectric media (e.g., LPG, light oils).

• Features: Immune to dust/steam but requires direct medium contact.

3. Core Advantages of Radar Level Transmitters

4. Typical Applications

(1) Oil & Gas Industry

• Media: Crude oil, diesel, acids/alkalis.

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  Challenges: High temp/pressure, corrosion.

• Recommended: 26GHz radar with PTFE-coated antenna.

(2) Food & Pharmaceutical

• Media: Milk, syrups, pharmaceutical ingredients.

• Challenges: Hygienic requirements, FDA compliance.

• Recommended: 80GHz radar with food-grade stainless steel/PEEK.

(3) Power & Energy

• Media: LNG, slurry, desulfurization liquids.

• Challenges: Cryogenic temps, high viscosity.

• Recommended: Guided wave radar for low-dielectric media.

5. Key Selection Criteria

Consider these parameters when selecting a radar transmitter:

1. Medium Properties: Dielectric constant, corrosiveness, viscosity.

2. Process Conditions: Temperature, pressure, foam/steam presence.

3. Measuring Range: Short-range (0-5m) → 80GHz; long-range (30m+) → 26GHz.

4. Mounting: Flange, threaded, or probe-style installation.

5. Output: 4-20mA, RS485, or wireless (LoRa/NB-IoT).

Common Pitfalls:

• ❌ Ignoring dielectric constant: Low-Dk media (e.g., LPG) need guided wave radar.

• ❌ Overlooking installation: High dust/steam requires 80GHz FMCW radar.

6. Maintenance & Troubleshooting

• Routine Checks: Inspect antenna for buildup; verify seal integrity.

• Common Issues:

• Signal loss → Clean antenna or check alignment.

• Erratic readings → Assess turbulence/foam interference.

• Longevity Tips:

• Use PVDF/PTFE-coated antennas in corrosive environments.

• Avoid mounting near inlet pipes to minimize turbulence.

Conclusion

Radar level transmitters deliver unmatched precision, reliability, and adaptability, making them the top choice for industrial level measurement. Proper selection and maintenance can significantly boost operational efficiency while reducing lifecycle costs.

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