Level Sensors & Switches

RLI-80 Non-Contact Radar

Part Number:
RLI-80 Non-Contact Radar Level Sensor
Image is of similar product


The RLI-80 Non-Contact Radar Level Sensor is a no-moving parts continuous level transmitter for reliable performance in challenging OEM and industrial tank level applications. RLI-80 Non-Contact Radar comes standard with 4–20 mA, Modbus, and Bluetooth® connectivity for configuration and setup. The RLI-80 provides accurate level measurement in medias with a dielectric constant of 2 or greater. Constructed of chemically inert PVDF material and designed to withstand IP67 conditions, the RLI-80 withstands the harshest conditions. The 2" NPT mounting provides adaptability to be used in tanks as large as 49.2 ft (15 m). The RLI-80 is unaffected by changes in physical properties of the application such as pressure, temperature, or vapors.

CE ROHS Gems Compliant CSA


  •  Non-contact
  • 2" NPT mounting
  • PVDF housing
  • Intrinsically Safe
  • UL/c-UL
  • ATEX
  • IECEx
  • 15m sensing range
  • 5mm accuracy
  • Modbus
  • 4-20mA
  • Bluetooth®
  • IP 67
  • 15' or 30' TPE Jacketed Cable
  • 1 ¼”-12 For Bracket Mounting
  • Full vacuum to 43 PSI
  • -40 to 80C.    
Sensor Type
Non-Contact Continuous Level Sensor
Up to 15m (49.2ft) 
±5mm (0.2 inch)
Beam Width
8 Degrees
Supply Voltage
24-36 VDC 
Signal Output
4-20mA or Modbus®
Minimum Process Temperature
Maximum Process Temperature
Vacuum to 43 PSI (3 Bar)
Electrical Connection
15' or 30' TPE Jacketed Cable

RLI-80 Datasheet

Format .pdf
Size 710 KB

RLI-80 Legacy Products Cross-Over

Format .pdf
Size 681 KB

Bracket Assembly Sheet, Part # 261977

Format .pdf
Size 162 KB

RLI-80 Non-Contact Radar Level Sensor Spec Sheet

Format .pdf
Size 205 KB

RLI Series Technology Comparison

Format .pdf
Size 223 KB

RLI-80 Product Guide

Format .pdf
Size 746 KB
  • Food & Beverage - Brewery
  • Food & Beverage - Brewing Equipment
  • Food & Beverage - Dairy
  • Food & Beverage - Food Processing
  • Food & Beverage - Other
  • Food & Beverage - Systems Integrator- OEM- both
  • General Industry - Chemical Metering/Injection
  • General Industry - Fire Protection
  • General Industry - Fuel - Handling
  • General Industry - Hydraulics
  • General Industry - Printing - 3D
  • General Industry - Printing Equipment
  • General Industry - Service Cart
  • General Industry - Tanks
  • General Industry - Tanks - Specialty Chem
  • HVAC/R - Chillers
  • HVAC/R - Cooling
  • HVAC/R - Cooling Towers
  • HVAC/R - Evaporators
  • HVAC/R - General HVAC
  • Marine - Commercial - Container Ships
  • Marine - Commercial - Cruise Ships
  • Marine - Commercial - Other
  • Marine - Commercial - Pleasure Craft
  • Marine - Commercial - Ship Owner
  • Marine - Commercial - Ship Systems
  • Marine - Commercial - Shipbuilder
  • Marine - Commercial - Workboats
  • Marine - Commercial - Yachts
  • Marine - Govt & Military - Homeland Security
  • Marine - Govt & Military - Marine
  • Marine - Govt & Military - Marine - Other
  • Marine - Govt & Military - Military
  • Marine - Govt & Military - US Government
  • Medical - Lab
  • Medical - Laboratory & Testing
  • Medical - Life Sciences
  • Medical - Other
  • OHV - Agricultural Equipment
  • OHV - Construction Equipment
  • OHV - Fertilizer
  • OHV - Fire Trucks
  • OHV - Forestry Equipment
  • OHV - Highway Construction Equipment
  • OHV - Industrial Equipment
  • OHV - Military Vehicles
  • OHV - Mining Equipment
  • OHV - Recreational Vehicles
  • OHV - Specialty Equipment
  • Oil & Gas - Drilling Equipment
  • Oil & Gas - Energy - Oil/Elec/Gas/H2O
  • Oil & Gas - Enhanced Oil Recovery-EOR
  • Oil & Gas - Exploration
  • Oil & Gas - Extraction & Distribution Equip.
  • Oil & Gas - Mud
  • Oil & Gas - Offshore Platforms
  • Oil & Gas - Oil Water Separators
  • Oil & Gas - Other
  • Oil & Gas - Storage Tanks
  • Power Generation - Generators
  • Power Generation - Green Energy
  • Power Generation - Power Generating Facilities
  • Power Generation - Transformers
  • Power Generation - Turbines
  • Process Industry - Chemical
  • Process Industry - Other
  • Process Industry - Processing
  • Process Industry - Pulp & Paper
  • Process Industry - Sanitary
  • Process Tanks
  • Transportation - Fire Trucks
  • Transportation - Rail - Locomotive
  • Transportation - Rail - Other
  • Transportation - Specialty Vehicles
  • Water & Waste Water - Chemical Metering/Injection
  • Water & Waste Water - Flood Level Monitoring
  • Water & Waste Water - Industrial Water Treatment
  • Water & Waste Water - Other
Is one radar sensor sufficient to provide level measurement and overfill protection at the same time?

Yes, one sensor is sufficient. A redundant solution will provide more security, but Gems RLI-80 non-contact radar sensor can measure accurately even in high vapor, high turbulent applications.  

How do radar sensors react to waves?

The influence of waves or turbulent water surfaces is minimal. With a wide dynamic range, Gems RLI-80 radar sensor measures even the smallest signals and can compensate for water movement very well. Moving surfaces are a standard feature in water applications.  Regardless of whether a container is being filled or pumped down Gems RLI-80 radar sensor calculates an average value from multiple reflected signals.

Do radar sensors measure through surface sludge?

Sludge is very compact, and the microwave signal cannot pass through it. However, the surface height of the sludge can be detected accurately, allowing a reliable level measurement. In contrast to foam, which is generally easier to measure through, this does not work with sludge. If it is necessary to determine the exact height of the sludge, this can be done by combining a radar sensor and a pressure sensor. The radar sensor detects the sludge surface, and the pressure sensor detects the water level using hydrostatic pressure. The differential indicates the thickness of the sludge because its density is significantly different from that of water.

Response rate of the RLI-80?

The response rate, or how fast the sensor reacts to a change in the measurement output, depends on the type of output.  RLI-80 sensors with 4-20mA outputs have a response rate of 2.5 seconds.  RLI-80 sensors with Modbus outputs have a response rate of 0.5 seconds. 

What approvals does the RLI-80 have?

The RLI-80 will have the following Intrinsically Safe approvals*: UL/c-UL for Class I, Division 1, Groups A, B, C, and D; Class II, Division 1, Groups E, F, and G; Class III, Division 1; Zone 0, Group IIC, AEx/Ex ia IIC T4 Ga; and ATEX/IECEx/UKEx Zone 0, Group IIC, II 1G Ex ia IIC T4 Ga.  The sensor requires appropriate intrinsically safe barriers to render the sensor intrinsically safe.  Please see the Data Sheet for more information on suggested barriers and the wiring diagrams. *Approvals scheduled to be complete in May 2022.  Contact Gems for approvals certificates.

Do radar sensors also measure bulk solids?

Yes, Gems RLI-80 non-contact radar level sensor is suitable for measuring bulk solids. The measuring ranges are the same for liquids and solids.  Gems RLI-80 radar sensor is not only suitable for water and wastewater, but also for other media with dielectric constants of 2 or greater.  From water-based products, chemicals, acids, and alkalis to auxiliary substances used in the wastewater industry and chemical products. They can also be used in all kinds of bulk solids applications like building materials, grain, and many others.

Are there signal outputs other than 4 to 20 mA?

Yes, Gems RLI-80 non-contact radar level sensor comes standard with 4-20mA output/HART, and Modbus.  With Modbus, the instruments can be easily connected to existing data loggers.  Gems’ radar level sensor also comes standard with Bluetooth connectivity for simple configuration and diagnostics.  Review all the specifications here. 

Does the sensor always need a controller?

No, Gems RLI-80 non-contact radar level sensor has 4-20 mA, Modbus, or HART directly as cable output. However, using a controller makes sense if, for example, an additional display is needed to provide more clarity on site. Pump or valve control can also be realized with a controller.

Are there any disadvantages to radar?

No, radar technology is not affected from moisture, vapor, or dust in the air like Ultrasonic sensors are.  With competitive prices for Gems RLI-80 non-contact radar sensor it is a simple decision to switch to radar technology.

How do you calculate the beam width of the Radar signal?

Gems RLI-80 non-contact radar level sensor sends out an 8-degree beam. Please review the beam width calculator to calculate the width at various tank depths.  The beam can encounter the side of the tank, if there are no obstructions on the outside of the tank, as those can reflect the signal and cause an inaccurate reading.

Can you place the Non-Contact Radar Sensor in a standpipe?

Yes, Gems RLI-80 non-contact radar level sensor can be placed in a metal standpipe, 2.5” minimum diameter.

What is dielectric constant?

Dielectric Constant is the ratio of the permittivity of a material to the permittivity of free space.  In other words, it is the measurement of electric flux that will concentrate within a material.  Gems RLI-80 radar level sensor requires a dielectric constant of 2 or greater.  Learn more about dielectric constant and common liquids with proper dielectric constant to work with Gems RLI-80 radar level sensor here.  You do not need to set the dielectric; the sensor will work automatically if the media has a dielectric of 2 or greater.