1.High frequency and low frequency: a table to explain clearly
🟠 Low frequency radar
Representative: 6 GHz/10 GHz
The wavelength is about 30-50 mm
Large antenna size (thick horn mouth)
Beam width (15 °~30 °)
Measurement accuracy ± 5-10 mm
The range can reach 20-30 meters
Foam penetration ✅ strong
Corrosion gas adaptation ✅ Good
Applicability of small cans ❌ Poor (beam hitting tank wall)
Low price
🟢 High frequency radar
Representative: 26 GHz/80 GHz
Wavelength approximately 3.7-11 mm
Small antenna size (can be used as a planar antenna)
Narrow beam angle (3 °~8 °)
Measurement accuracy ± 1-2 mm
Range 30-100m (80G type)
Foam penetration ❌ Weak (will be absorbed by foam)
Corrosion gas adaptation ⚠️ Sealing needs to be considered
Applicability of small cans ✅ Okay (beam concentration without hitting walls)
High price (especially expensive for 80G)
⚠️ Important reminder: The term 'strong penetration' should be carefully interpreted in the field of radar level gauges——
The low-frequency radar has a stronger ability to penetrate foam and steam, because the long wavelength is not easy to be scattered by the bubbles in the foam. The high-frequency radar signal has high energy concentration and resolution, but it is more sensitive to the attenuation of foam and water vapor. Both can not penetrate the liquid surface itself - radar measures the reflection of the liquid surface, not penetration!
2, Why has 80 GHz radar become mainstream in recent years?
Around 2015, a large number of 80 GHz broadband frequency modulated continuous wave (FMCW) radar level gauges entered the market and quickly became mainstream in the industry.
There are several key reasons behind this:
Leap in measurement accuracy:
80 GHz+broadband FMCW technology, with an accuracy of ± 1 mm, an order of magnitude improvement compared to the old 6 GHz model's ± 5 mm
Antennas can be made extremely small:
The 80 GHz wavelength is only 3.7 mm, and with a planar array antenna, the overall size can be made very small, making it easy to install on small containers and pipelines
Extremely narrow beam angle:
Approximately 3 ° to 4 °, almost unaffected by interference from the internal components of the tank, greatly simplifying the setting of "false echo suppression"
Larger range:
Some models can reach up to 100 meters, covering almost all industrial storage tanks
Rapid price decline:
After large-scale production, the price of the 80 GHz model has approached 26 GHz, demonstrating its cost-effectiveness advantage
⚠️ Shortcomings of 80 GHz:
① Concentrated foam working condition (such as fermentation tank and papermaking black liquor) - foam absorbs high frequency signals, so low-frequency or guided wave radar is still recommended
② The requirements for high-temperature and high-pressure steam seals are stricter, and the design of sealing materials and structures is more complex
③ In highly corrosive gas environments, the lifespan of antenna seals needs to be evaluated with emphasis
3, Suggestions for frequency selection under different operating conditions
✅ Prioritize 80 GHz
Small container (DN<1000mm)
A reaction tank with stirring blades and heating coils
Bypass pipe liquid level measurement
Accurate measurement of solid material bin
High precision trade measurement storage tank
Requires extremely small installation diameter (below DN50)
🟠 Prioritize selecting 6 GHz low frequency
There is a large amount of continuous foam on the surface of the medium
High temperature storage tank (with concentrated water vapor)
Large vertical storage tank (range>30 m)
Highly corrosive volatile gases (chlorine, ammonia)
Low precision requirements and price sensitive projects
🔵 Positioning at 26 GHz
Transition selection between high and low frequencies
Medium sized storage tank (DN 1000-3000mm)
Mild foam working condition
It has been widely applied and the supply of spare parts is mature
🔴 In situations where radar level gauges are not suitable
Vacuum tank (without atmospheric medium, unable to propagate microwaves? - No! Microwaves propagate better in vacuum)
The dielectric constant of the medium is extremely low (such as liquefied gas with ε<1.5) - the reflection is extremely weak, and guided wave radar is recommended
The tank body is a metal mesh structure (signal leakage)
Intense turbulence/splashing without liquid surface
💡 Vacuum tank description: Microwaves (electromagnetic waves) propagate unaffected in vacuum (with a speed equal to the speed of light), and radar level gauges are fully usable in vacuum tanks, even more accurate than in environments with gas (eliminating gas refractive index correction errors).
