Understanding Radar Level Transmitter Classification
Radar level transmitters are essential instruments in industrial process control, widely used for measuring liquid and solid levels in storage tanks, silos, and reactors. Choosing the right radar level transmitter requires a solid understanding of the two key classification dimensions: measurement method (non-contact vs. contact) and operating frequency (6G, 26G, or 80G).
1. Classification by Measurement Method
| Type | Principle | Best For |
|---|
| Non-Contact Radar | Antenna emits electromagnetic waves toward the medium surface without touching the liquid or solid. | Most liquid and solid level measurements, large storage tanks, high-temperature applications. |
| Contact Radar (Guided Wave) | Electromagnetic pulse travels along a probe or cable; signal reflection occurs at the medium interface. | Small measuring ranges, heavy steam, low dielectric constant media, narrow tanks. |
2. Classification by Working Principle
Pulse Radar (6G/26G): Emits ultra-short microwave pulses and measures the time-of-flight for the reflected signal. Simple structure, cost-effective, accuracy of ±3-10mm. Suitable for standard operating conditions.
FMCW Radar (Frequency Modulated Continuous Wave, 80G): Continuously transmits a frequency-swept signal and calculates distance by measuring the frequency difference between transmitted and reflected waves. Accuracy up to ±1mm, superior anti-interference capability. The industry trend is clearly moving toward 80G FMCW technology for its narrower beam angle and higher precision.
Non-Contact Radar: Antenna Types Explained
The antenna is the 'eye' of a non-contact radar—different antenna forms determine the beam angle, anti-condensation performance, and suitability for various operating conditions.
Horn Antenna
Shaped like a horn, with a PTFE emitter inside. Larger horn diameter produces a narrower beam angle and stronger signal focusing. Best for: Solid level measurement (cement silos, coal bunkers, ore bins) and long-range liquid tanks. Limitation: In liquid applications, steam condensation on the internal PTFE emitter can interfere with signals, requiring purge systems or regular cleaning.
Droplet Antenna
Specifically designed to prevent condensation buildup. The droplet shape allows condensed water to flow off the surface naturally, preventing signal interference. Primarily used in 26G high-frequency radar. Best for: High-steam liquid measurement applications. Note: Now largely replaced by the more cost-effective planar cone antenna.
Rod Antenna (PTFE Full Anti-Corrosion)
Exterior fully constructed from PTFE with a 304 stainless steel internal horn. All wetted parts are PTFE, providing complete corrosion resistance. Best for: Strongly corrosive liquids (acids, alkalis, salt solutions). Recommended measuring range of 5-10 meters.
Planar Cone Antenna
An upgraded version of the rod antenna, also made from 304 stainless steel + PTFE material. Offers improved anti-condensation performance at a lower cost than droplet antennas. Best for: Anti-corrosion liquid measurement—currently the mainstream choice for 26G radar liquid applications.
Parabolic Antenna
Uses parabolic reflection principles to achieve the narrowest beam angle and strongest signal focusing. Best for: Ultra-long-range measurement and environments with strong interference.
Lens Antenna (80G Standard)
The standard antenna for 80G FMCW radar. Electromagnetic waves are focused through a dielectric lens, achieving an extremely narrow beam angle (<3°). Best for: Complex operating conditions—high temperature, high pressure, heavy steam, dense dust, agitators, and obstacles. Especially suitable for narrow tanks and reactors.
Guided Wave Radar (GWR): The Contact Solution
Guided Wave Radar operates on the Time Domain Reflectometry (TDR) principle. Electromagnetic pulses travel along a probe or cable, and the signal is reflected at the liquid interface. Since the signal is confined within the probe, it is immune to tank internals, foam, and agitation.
| Probe Type | Application | Max Range |
|---|
| Single Rod | Liquid measurement | ≤4m |
| Single Cable | Liquid and solid measurement | Up to 30m |
| Twin Rod | Low dielectric constant liquids | ≤4m |
| Coaxial | Heavy steam, low dielectric constant | ≤6m |
Key Advantages: Stable signals unaffected by surface turbulence, foam, or tank internals; measurement independent of medium density; easy calibration; minimal blind zone. Limitations: Not suitable for highly corrosive or high-viscosity media; probe must be installed vertically without bending.
Non-Contact vs. Contact: Quick Comparison
| Parameter | Non-Contact Radar | Guided Wave Radar |
|---|
| Measurement Method | Electromagnetic wave in space | Signal along probe/cable |
| Contact with Medium | No | Yes |
| Maximum Range | 70-120m | ≤30m |
| Blind Zone | 0.3-0.5m | Very small |
| Affected by Tank Internals | May cause false echoes | Immune |
| Cost | Higher (80G) | Lower |
Frequency Selection: 6G, 26G, or 80G?
| Frequency | Beam Angle | Accuracy | Best For |
|---|
| 6GHz | ~30° | ±10-15mm | Legacy installations, heavy foam, thick steam, high dust—longest wavelength for best penetration |
| 26GHz | 8°-12° | ±3-5mm | General-purpose liquid and solid measurement; best cost-performance ratio for standard applications |
| 80GHz | 2°-4° | ±1mm | Complex conditions, high-precision metering, narrow tanks, reactors with agitators |
Important: While 80GHz offers the highest precision, its penetration capability is the weakest among the three. In applications with thick foam, heavy steam, or high-concentration dust, 6GHz or 26GHz may actually perform better due to longer wavelength penetration.
Quick Selection Summary
- Liquid measurement (standard): Planar cone antenna (26G) or lens antenna (80G)
- Solid measurement: Horn antenna—narrow beam angle, strong signal focusing
- Corrosive media: Rod antenna or planar cone antenna (PTFE full anti-corrosion)
- Complex conditions (high temp/pressure/steam): 80G lens antenna
- Small range + heavy steam: Guided wave radar (single rod or coaxial)
- Low dielectric constant (light oil, LPG): Guided wave radar—stronger echo signal
For more information on radar level transmitter solutions tailored to your specific application, contact our engineering team today.
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