What Is a Non-Contacting Radar Level Transmitter?
A non-contacting radar level transmitter is a continuous level instrument mounted on the top connection of a tank that sends a microwave signal through an antenna with no physical contact with the product. The signal is reflected by the product surface and returns to the antenna; the device turns the information corresponding to the round-trip time into a distance, and the distance into level, ullage or volume.
Because the measurement relies on an electromagnetic wave traveling through air or the tank atmosphere, the density, viscosity, temperature, pressure and pH of the product do not affect the result. The absence of moving parts and top mounting reduce maintenance needs and the risk of leaks. For this reason the radar level transmitter is chosen for a wide range of applications, from corrosive chemicals to viscous products and from open-air sumps to dust-laden silos.
The devices covered on this page are two-wire FMCW radars operating in the 80 GHz class. The high frequency produces a narrow beam from a small antenna, so stable measurement is possible on process connections from ¾-inch threads to 6-inch flanges and despite internal structures such as pipes, ladders and heating coils. Where the dielectric constant of the product is very low, the interface between two liquids has to be measured or the measurement must be made inside a narrow chamber, guided wave radar level transmitters should be considered instead.
How 80 GHz FMCW Radar Works
Instead of sending pulses, FMCW radar uses a continuous signal whose frequency changes linearly over time, and calculates distance from a frequency difference rather than a time difference. The measuring chain can be summarized in five steps:
1. Frequency sweep: The transmitter generates a continuous microwave signal whose frequency is swept rapidly across the 77–81 GHz band and sends it through the antenna toward the product surface. Maximum output power is +5 dBm (3.2 mW).
2. Reflection from the surface: The signal is reflected at the boundary formed by the dielectric constant difference between the tank atmosphere and the product and returns to the antenna. The strength of the reflection depends on the dielectric constant of the product and the condition of the surface.
3. Measuring the frequency difference: By the time the reflected signal reaches the antenna, the transmitter is already emitting at a different frequency. The frequency difference between the transmitted and received signals is proportional to the round-trip time of the signal and therefore to the distance to the surface.
4. Building the echo profile: Spectral analysis converts the frequency differences into an echo profile. The software tracks all echoes — from the product surface, tank internals and the tank bottom — and separates the true surface echo from disturbing reflections.
5. Level calculation and output: The level is found by subtracting the surface distance from the reference height; if required, volume is calculated from the tank geometry. The result is passed to the control system as a 2-wire 4–20 mA signal with superimposed HART digital data.
How High Frequency Affects the Beam Angle
For a given antenna diameter, the beam becomes narrower as the frequency rises. In the 80 GHz class the process seal antenna and the open-air lens antenna have a beam angle of 8°, the 1–1½-inch lens antenna 9° and the ¾-inch lens antenna 12°. An 8° beam is about 1.4 m wide at a distance of 10 m and about 4.2 m wide at 30 m. A narrow beam reduces reflections from the tank wall and internal structures and makes it easier to measure through small nozzles.
Echo Tracking and Rejection of Disturbing Reflections
Advanced echo processing algorithms continuously track stationary echoes from obstacles in the tank and distinguish them from the moving product surface. This approach provides reliable measurement in small tanks and fast-filling vessels as well. The default maximum level rate is 40 mm/s and can be increased to 200 mm/s depending on the application.
Characteristics of Measurement in Solids
The surface of bulk solids is not flat: the material forms a cone according to its angle of repose, and dust clouds can form during filling. Solids usually have a low dielectric constant (of the order of 1.2 for light powders, 1.35 for plastic granules, 1.5 for cement, sand, lime powder and grain, and 1.7 for wood chips and wood pellets). The achievable measuring range in solids therefore varies between 10 and 30 m depending on antenna type and product; silo diameter, internal obstacles, condensation and build-up on the antenna also affect the range.
Because FMCW radar emits its signal continuously but at low power, it provides energy-efficient measurement and can run on two-wire loop power. The frequency setting must be chosen to comply with the radio spectrum regulations of the country in which the device will be operated.
Key Features
· Two accuracy classes: Under reference conditions, ±2 mm accuracy in the standard class and ±1 mm in the high-accuracy class; repeatability ±0.5 mm.
· Three antenna types: A lens antenna for small process connections, a process seal antenna with wetted parts entirely in PTFE, and a lens antenna with a bracket mounting option for open-air and non-pressurized tanks.
· Measurement up to 30 m in liquids and solids: Maximum measuring range of 30 m in liquids (15 m with the ¾-inch threaded lens antenna); 10–30 m in solids depending on product and antenna.
· Wireless access via Bluetooth: The Bluetooth option, supplied together with the graphical display, allows wireless configuration and maintenance from a distance of at least 15 m with line of sight.
· Multilingual graphical display: The three-line graphical LCD offers menus in 14 languages, including Turkish; it shows selected variables and diagnostic alerts with NAMUR-compliant maintenance symbols.
· Proof testing without raising the level: By adding a virtual surface echo to the radar signal, the transmitter output, alarm limits and configuration can be tested without stopping the process or changing the level.
· Schedulable device verification: An automatic verification that checks the integrity of the transmitter without process interruption can be scheduled if required and produces a pass/fail report.
· Logging and diagnostics: Level and echo profile records covering the previous three days, together with the 50 most recent alerts, are kept in the device memory; early warnings are given for antenna build-up and abnormal surface conditions.
· Several devices on one tank: Multiple transmitters mounted on the same tank can operate without interfering with one another, which simplifies redundant measurement arrangements.
· Air purging for the antenna: Where heavy build-up is expected, the antenna can be cleaned through an air connection; flushing connection rings are offered as accessories for process seal antennas.
Technical Specifications
The values below are typical technical data for the 80 GHz FMCW non-contacting radar level transmitter covered on this page. Pressure and temperature limits vary with the antenna type and flange selection, and the measuring range with the product and installation conditions; final values should be confirmed at project stage.
Parameter | Technical data |
Measuring principle | FMCW (frequency modulated continuous wave), non-contacting |
Frequency range | 77–81 GHz (76–77 GHz in certain countries) |
Maximum output power | +5 dBm (3.2 mW) |
Reference accuracy | High-accuracy class ±1 mm · standard class ±2 mm (15–25 °C, fixed metal plate target, process seal antenna) |
Repeatability | ±0.5 mm |
Ambient temperature effect | ±1 mm / 10 K |
Maximum measuring range | 30 m (15 m with the ¾-inch threaded lens antenna); 10–30 m in solids depending on the product |
Update rate | At least 1 Hz (with 15 Vdc supply at 4 mA) |
Maximum level rate | Default 40 mm/s, adjustable up to 200 mm/s |
Antenna types and beam angle | Process seal antenna 8° · lens antenna ¾-inch 12°, 1–1½-inch 9° · open-air lens antenna 8° |
Process pressure | Process seal and lens antenna: –1…25 bar · open-air lens antenna: –1…0.5 bar |
Process temperature | Process seal and lens antenna: –60…200 °C · open-air lens antenna: –20…80 °C (–40…80 °C in open-air applications) |
Ambient and storage temperature | –40…80 °C (may be limited depending on process temperature) |
Materials exposed to the tank atmosphere | PTFE; 316/316L (EN 1.4404) threaded connection on the lens antenna; anodized aluminum and FKM O-ring on the open-air lens antenna |
Process connection | ¾, 1 and 1½-inch NPT or BSPP (G) threads; 2–6 inch / DN50–DN150 / 50A–150A flanges (ASME B16.5 Class 150/300, EN 1092-1 PN16/PN40, JIS 10K/20K) |
Output | 2-wire 4–20 mA, HART digital communication (multidrop supported); optional Bluetooth |
Electrical supply | Max. 35 Vdc and 22.5 mA at the terminals (max. 30 Vdc in intrinsically safe installations); internal power consumption < 0.8 W |
Ingress protection | Process seal and lens antenna: IP66/67/68, NEMA 4X · open-air lens antenna: IP65, NEMA 4X |
Start-up time | < 60 s |
Accuracy values are given according to IEC 60770-1, excluding installation-dependent constant offset. In the near zone and at distances close to a strong tank bottom echo, actual performance depends on the product and application conditions.
Key Advantages
· Measurement without product contact: Because the antenna does not touch the product, contamination, wear and cleaning needs are reduced with sticky, viscous or corrosive products.
· Independence from process variables: Changes in density, viscosity, temperature, pressure and pH do not affect the measurement, and no recalibration is required when the product changes.
· Small connections and obstructed tanks: The narrow beam allows measurement through ¾-inch threaded connections and reduces disturbing echoes in tanks with internal structures.
· Long service life in corrosive media: An antenna with wetted parts entirely in PTFE suits corrosive environments and applications with dust and heavy condensation.
· Safe and fast commissioning: Configuration via Bluetooth without entering the hazardous zone, illustrated guidance and a user-friendly software interface shorten commissioning time.
· Longer proof test intervals: Remote proof tests and automatic verification allow safety functions to be documented without process interruption.
· Energy-efficient two-wire design: The transmitter runs loop-powered with an internal power consumption below 0.8 W in normal operation; no separate power cable is needed.
· Predictive maintenance: Warnings about antenna build-up and signal quality help plan maintenance before a failure occurs.
Application Areas
Non-contacting radar level transmitters are used across a wide range of processes for continuous level measurement of liquids, slurries and bulk solids. The main application types are summarized below.
Storage Tanks
Used to monitor correct filling and stock levels. Where multi-tank sites need inventory management and system-level measurement, the transmitters should be assessed together with tank gauging systems.
Mixing and Process Tanks
In mixing tanks, echo tracking algorithms separate reflections from tank internals from the real product surface and help keep the process under continuous observation; in pressurized process vessels, process seal and lens antennas can be used up to 25 bar.
Corrosive and Condensing Environments
For tanks in which corrosive chemicals are stored or processed, the process seal antenna with wetted parts entirely in PTFE is preferred; the same antenna is also an advantage in atmospheres with heavy condensation and dust.
Open-Air Applications
Level is measured in sumps, ponds and open channels despite difficult surface and weather conditions. The bracket-mountable open-air lens antenna can be used in a temperature range of –40…80 °C in open-air applications.
Bulk Solids Silos
For solids such as cement, sand, lime powder, plastic granules, grain, bran, wood chips and wood pellets, measurement is unaffected by dust and low reflectivity. For solids, mounting the device at a distance from the tank wall of two-thirds of the silo radius is recommended.
Safety Applications
The SIL 2 certified transmitter can be used in safety functions including dry-run prevention, overfill prevention and level range monitoring; proof tests can be carried out without raising the level.
How to Select a Radar Level Transmitter
Successful measurement with non-contacting radar depends on choosing the right antenna type, process connection and mounting position for the application. For a technical assessment we recommend collecting the following information:
Process and Product Conditions
· Product to be measured: liquid, slurry or solid; for solids, the particle form (powder, granule, pellet) and approximate dielectric constant
· Required measuring range and accuracy class (standard ±2 mm or high accuracy ±1 mm)
· Process temperature and pressure (–60…200 °C, –1…25 bar for process seal and lens antennas)
· Risk of foam, turbulence, condensation and build-up on the antenna; need for air purging if required
· Maximum filling and emptying rate (default 40 mm/s, up to 200 mm/s)
Antenna and Process Connection
· Size of the existing nozzle or connection: lens antenna for ¾–1½-inch threaded connections, process seal antenna for 2–6-inch flanges
· Wetted material compatibility: wetted parts entirely in PTFE, or a lens antenna with a 316/316L body
· Bracket-mounted open-air lens antenna for non-pressurized or open-air applications
· Flange standard and pressure rating (ASME Class 150/300, EN 1092-1 PN16/PN40, JIS 10K/20K)
Mounting Position and Nozzle
· The device should not be mounted in the tank center, above or close to the fill stream, on a manhole cover or directly above a side manhole door
· Distance to the tank wall should be at least 200 mm; the recommended distance is half the tank radius for liquids and two-thirds of the radius for solids
· The device should be mounted vertically, with an inclination not exceeding 3°
· The inside of the nozzle should be smooth; nozzle height is limited according to diameter (e.g. for a 2-inch nozzle, 200 mm with the lens antenna and 500 mm with the process seal antenna)
· For tanks made of non-metallic material, keep objects located just outside the tank wall out of the beam
Electrical, Communication and Safety
· Supply voltage and loop resistance (at least 250 Ω for HART communication)
· Alarm direction and levels (manufacturer standard or NAMUR NE 43)
· Bluetooth, graphical display and language requirements
· Hazardous area classification and required type of protection
· SIL requirement, proof test method and need for verification reports
In applications with heavy foam where the surface echo may remain weak, or in vessels that need local visual indication, other measurement technologies should also be compared. TLY Enerji carries out this assessment together with you on the basis of process data.
Functional Safety, Hazardous-Area and Radio Approvals
The main certifications, approvals and standards available for the non-contacting radar level transmitter are summarized below. The scope of approval depends on the selected configuration.
Standard / approval | Scope and description |
IEC 61508 – Functional Safety | Type B element in low and high demand mode; random hardware integrity of SIL 2 for HFT=0 and SIL 3 for HFT=1, with SIL 3 systematic capability. Option for a safety certificate with FMEDA data. |
ATEX and IECEx | Flameproof, dust ignition-proof and intrinsically safe types of protection, plus protection type options for use in Zone 2; country approvals for North America, Brazil, China, Japan, Korea, India and the Eurasian Economic Union (EAC). |
NAMUR | NAMUR type-tested design; NE 21 electromagnetic compatibility recommendation, NE 43 alarm and saturation levels, NE 107 standardized field diagnostics. |
Radio Approvals | Level probing radar standards ETSI EN 302 372 (closed tanks) and ETSI EN 302 729 (open air) under the Radio Equipment Directive 2014/53/EU, EN 300 328 for Bluetooth; FCC and Canadian radio approvals. |
EMC, Pressure Equipment and Lightning Protection | EN 61326-1 and EN 61326-2-3 under the EMC Directive 2014/30/EU; compliance with Article 4.3 of the Pressure Equipment Directive (PED) 2014/68/EU; 2 kV built-in lightning protection to IEC 61000-4-5. |
Vibration Resistance | 2 g in the 10–1000 Hz range to IEC 61298-3 (excluding the mounting bracket option). |
NACE and Material Documentation | Material recommendation to NACE MR0103/ISO 17945 and NACE MR0175/ISO 15156, EN 10204 3.1 material traceability certificate, and hydrostatic test, liquid penetrant and positive material identification certificates. |
Marine Type Approvals and Overfill Prevention | Type approvals from American Bureau of Shipping, DNV, Lloyd's Register and Bureau Veritas (aluminum housing only in enclosed spaces such as machinery and pump rooms); overfill prevention approval option under the German Water Resources Act (WHG). |
Ingress Protection | IP66/67/68 (45 minutes at a depth of 3 m) and NEMA 4X for versions with process seal and lens antennas; IP65 and NEMA 4X for the open-air lens antenna. |
Certificate markings, temperature classes and safety manual conditions are assessed at project stage by the TLY Enerji engineering team together with the relevant product certificates.
Radar Level Measurement Solutions from TLY Enerji
TLY Enerji treats radar level measurement together with the tank itself. Our engineering team evaluates the type of product and its dielectric behavior, the tank geometry, nozzle dimensions, internal structures, fill points and the risk of foam and condensation, and then defines the antenna type, process connection and mounting position. For applications as different as solids measurement in a silo, an open-air sump or a corrosive chemical tank, we present the suitable configuration together with the reasoning behind it.
We also support customers with the assessment of hazardous-area and SIL requirements, project documentation, PLC/DCS/SCADA integration via HART, on-site configuration via Bluetooth, echo profile checks during commissioning and the planning of proof test procedures. Our aim is for the radar measurement to be a verifiable data source with predictable maintenance from day one.
Frequently Asked Questions
How does a radar level transmitter work?
A non-contacting radar level transmitter sends a microwave signal from its antenna to the product surface and receives the signal reflected back from the surface. With the FMCW technique the signal frequency is swept continuously, and the frequency difference between the transmitted and received signals is proportional to the distance to the surface. The device subtracts this distance from the reference height to calculate the level and passes it to the control system as a 4–20 mA/HART signal.
What does 80 GHz frequency contribute to level measurement?
The high frequency makes it possible to achieve a narrow beam with small antennas. For the devices on this page, the beam angle is between 8° and 12° depending on the antenna. A narrow beam reduces disturbing echoes from the tank wall and from internal structures such as ladders, pipes or heating coils, and allows measurement through small threaded connections such as ¾ inch. In tall, narrow tanks the measurement also stays focused on the surface.
How do you choose between non-contacting radar and guided wave radar?
Non-contacting radar is usually the first choice where contact with the product is not wanted, for sticky or corrosive products, in tanks too tall for a probe and in silos. Guided wave radar may be more suitable when the interface between two liquids must be measured, the dielectric constant is very low, the measurement is made in a narrow bypass chamber or heavy foam is present. The final choice should be based on product and tank data.
Can a radar level transmitter measure solids in silos?
Yes. The device can measure bulk solids such as cement, sand, lime powder, plastic granules, grain and wood pellets without being affected by dust or low reflectivity. The measuring range depends on the antenna and the product: with the process seal antenna, measurement up to 20 m is recommended for light powders and up to 30 m for granules and heavy powders. Silo diameter, angle of repose, internal obstacles and antenna build-up should also be taken into account.
Do foam, condensation and antenna build-up affect the measurement?
Heavy turbulence, foam and condensation combined with poorly reflecting products can reduce the measuring range. In applications with heavy condensation and dust, the process seal antenna with wetted parts entirely in PTFE is preferred. If thick build-up on the antenna is expected, an air purge connection can be used, and diagnostic functions report build-up as an early warning. In vessels where the surface echo weakens significantly, alternative technologies should be considered.
Which antenna is used for open-air and non-pressurized tanks?
The lens antenna designed for open-air use and tanks at atmospheric pressure is installed with a 1½-inch BSPP threaded connection or with a mounting bracket. This antenna is suitable for –1…0.5 bar pressure and –20…80 °C process temperature; in open-air applications the lower limit is –40 °C. Its ingress protection is IP65 and NEMA 4X. Sumps, ponds and open channels are typical applications.
How does configuration via Bluetooth work?
The Bluetooth option is supplied together with the graphical LCD display and typically allows a wireless connection to the device from at least 15 m with line of sight. Configuration, echo profile inspection and maintenance can therefore be carried out with compatible configuration tools without opening the housing cover or approaching the hazardous zone. The achievable range may vary with the orientation of the device, obstacles and the electromagnetic environment.
Can a radar level transmitter be used in SIL applications such as overfill prevention?
Yes. The device is certified to IEC 61508 for SIL 2 applications in a single-channel (HFT=0) architecture and for SIL 3 in a redundant (HFT=1) architecture, and it has SIL 3 systematic capability. Typical functions include dry-run prevention, overfill prevention and level range monitoring. A proof test using a virtual echo can be initiated remotely from the control room, without raising the level or stopping the process.
What should be considered when choosing the mounting position on a tank?
Place the device where it has an unobstructed view of the product surface, away from the tank center and outside the fill stream. Keep at least 200 mm from the tank wall; a distance of half the tank radius is recommended for liquids and two-thirds for solids. Inclination should not exceed 3°, the inside of the nozzle should be smooth and the nozzle height should be limited according to its diameter. Several devices can share one tank with no mutual interference.