Radar Water Level Sensor with RS485 Modbus

The NiuBoL radar water level sensor is a non-contact level measurement instrument designed for continuous monitoring of rivers, reservoirs, irrigation channels, drainage systems, flood-prone areas and other hydrological applications.

The sensor uses 77–79 GHz FMCW millimeter-wave radar to measure the distance between the radar antenna and the water surface. The standard configuration provides a 0.1–65 m measurement range, a 6° narrow beam angle, an approximately 10 cm blind zone and specified measurement accuracy of ±1 mm under defined measurement conditions.

With RS485 Modbus RTU, DC 10–30V power supply, low power consumption and IP67 protection, the sensor can connect to compatible RTUs, PLCs, data loggers and IoT gateways for automatic water-level acquisition and remote hydrological monitoring.

Radar Water Level Sensor Technical Specifications

How Does a Radar Water Level Sensor Work?

The radar water level sensor uses FMCW, or Frequency Modulated Continuous Wave, technology. The antenna transmits a high-frequency electromagnetic signal in the 77–79 GHz band toward the water surface while continuously varying the transmitted frequency.

The water surface reflects part of the radar energy back toward the sensor. The internal electronics compare the transmitted signal with the received echo and use the frequency difference to calculate the distance between the radar antenna and the water surface.

Because the measurement is non-contact, the sensing element does not need to be submerged in the water. This reduces direct exposure to sediment, floating debris, water-borne contamination and mechanical loads caused by flowing water.

What Does the Radar Water Level Sensor Measure?

The radar directly measures the distance between the radar reference point and the water surface. Water-level height, water depth or water-level elevation is then calculated using a known installation reference.

Water Level Height = Reference Height − Radar-to-Water Distance

For example, if the radar reference point is installed 10.0 m above the selected zero-level reference and the measured distance to the water surface is 4.2 m, the calculated water level is 5.8 m relative to that reference.

For river, reservoir and flood-monitoring projects, the installation reference should be surveyed and documented carefully so changes in radar distance can be converted into meaningful water-level data.

Why Use 77–79 GHz FMCW Radar?

6° Radar Beam and Installation Clearance

The radar measurement cone becomes wider as the distance between the sensor and the water surface increases. Although this sensor uses a narrow 6° beam, nearby structures still need to be considered during installation.

For preliminary installation planning, the approximate beam diameter can be estimated from the 6° full beam angle:

Beam Diameter ≈ 2 × Distance × tan(3°)

These values are geometric estimates for installation planning rather than guaranteed effective measurement-area limits. Actual radar performance also depends on the water surface, mounting orientation, surrounding structures and echo conditions.

Radar Water Level Sensor Wiring

The radar sensor combines DC power and RS485 communication in the field cable. The standard product image shows the sensor dimensions, cable structure and electrical connection information.

Use the wire identification supplied with the actual sensor as the final wiring reference because cable colors or connector configurations may differ for customized orders.

RS485 Modbus System Integration

The RS485 water level sensor can connect to compatible RTUs, PLCs, data loggers and IoT gateways for continuous data acquisition.

Radar Water Level Sensor → RS485 Modbus → RTU / Data Logger / PLC → 4G / Ethernet → Cloud Platform / SCADA / Private Server

The radar sensor itself provides local water-level measurement data through RS485. Cellular communication, Ethernet, Wi-Fi, MQTT, HTTP, cloud storage or private-server transmission requires a compatible data logger, RTU or IoT gateway.

When several RS485 devices share one communication bus, each instrument should use a unique device address. Power capacity, baud rate, polling interval, cable topology and termination should also be considered when designing the network.

Remote Radar Water Level Monitoring Station

A complete remote water-level monitoring station can include the radar sensor, mounting pole or cross arm, RTU or data logger, protective enclosure, communication antenna, solar panel, battery and lightning-protection components.

Solar-panel and battery capacity should be calculated from the complete station load, including the radar sensor, data logger, cellular communication equipment and any additional rainfall or environmental sensors. Sampling interval, upload frequency and required battery autonomy should also be considered.

Radar Water Level Sensor Installation

Install the radar above the water surface with the antenna directed toward a representative measurement area. The supporting structure should be rigid, and the radar beam should remain clear of unnecessary obstacles throughout the expected water-level range.

Radar vs Submersible Water Level Sensor

For reservoirs and open-water monitoring, the radar can be installed above the water surface without requiring a submerged pressure probe.

For applications where a submerged hydrostatic probe is preferred, see the submersible level transmitter range.

Radar vs Ultrasonic Water Level Sensor

Radar and ultrasonic sensors both provide non-contact level measurement, but they use different physical principles and respond differently to atmospheric and installation conditions.

Environmental Factors That Can Affect Radar Measurement

Millimeter-wave radar is well suited to outdoor hydrological monitoring, but field performance still depends on installation geometry, water-surface conditions and the surrounding environment.

Radar Water Level Sensor Applications

River monitoring is one of the main applications for non-contact radar because the sensor can remain above flowing water while continuously measuring changes in the water-surface position.

This non-contact water level sensor is suitable for projects where continuous water-level monitoring is required and direct immersion of the sensing element is undesirable.

River Water Level  •  Reservoir Monitoring  •  Flood Warning  •  Urban Waterlogging
Irrigation Channels  •  Hydrological Stations  •  Drainage Channels  •  Remote Water Monitoring

How to Select a Radar Water Level Sensor

For irrigation channels and drainage systems, the installation point should be selected so that the radar beam remains clear of channel walls, vegetation and structural obstructions throughout the expected water-level range.

Radar Water Level Sensor FAQ

Q1. What does a radar water level sensor directly measure?

A1. It directly measures the distance between the radar antenna and the water surface. Water-level height or elevation is calculated from that distance using the known installation reference.

Q2. What is the measurement range?

A2. The standard configuration on this page provides a 0.1–65 m measurement range. Extended range configurations up to 70 m may be available depending on project requirements.

Q3. What radar frequency does the sensor use?

A3. The sensor operates in the 77–79 GHz FMCW millimeter-wave band.

Q4. What is the beam angle?

A4. The specified beam angle is 6°. The beam becomes wider as the measurement distance increases, so installation clearance should be checked before mounting.

Q5. Does the sensor support RS485 Modbus?

A5. Yes. The sensor provides RS485 Modbus communication for integration with compatible RTUs, PLCs, data loggers and gateways.

Q6. Can the radar sensor operate in rain?

A6. Millimeter-wave radar is suitable for outdoor hydrological monitoring and normally remains operational during rainfall. Severe rain and highly disturbed water surfaces can still increase measurement noise, so field installation and filtering should be validated for the site.

Q7. Can it be used above wastewater?

A7. Yes. Non-contact radar can be useful where direct probe contact with wastewater is undesirable. Foam, vapor, condensation, surrounding structures and the reflective condition of the liquid surface should still be considered.

Q8. Does a radar water level sensor require maintenance?

A8. It generally requires less water-contact maintenance than a submerged probe because the sensor remains above the water. The antenna surface, mounting structure, cable, connectors and reference position should still be inspected periodically.

Q9. Can the data be transmitted through 4G?

A9. Yes. Connect the RS485 radar sensor to a compatible 4G RTU or IoT gateway. Cellular communication is not built into the standard radar sensor itself.

Q10. Can it be powered by a solar system?

A10. Yes. Its low power consumption makes it suitable for solar-powered remote stations. Solar-panel and battery capacity should be calculated from the complete station load, transmission interval and required backup duration.

Q11. Is ±1 mm accuracy guaranteed over the entire range at every site?

A11. No. ±1 mm is the specified sensor accuracy under defined measurement conditions. Actual field performance depends on measurement distance, installation geometry, water-surface conditions, unwanted echoes and environmental conditions.

Q12. What information is required for a quotation?

A12. Provide the maximum radar-to-water distance, highest and lowest expected water levels, installation structure, channel or reservoir dimensions, quantity, cable requirement, available power supply and whether remote communication or a complete monitoring station is required.

Request a Radar Water Level Sensor Quotation

For model selection and quotation, provide the maximum radar-to-water distance, highest and lowest expected water levels, installation structure, available beam clearance, quantity, required cable length and power supply.

For remote hydrological monitoring projects, also specify whether you require an RTU, 4G communication, rainfall sensor, surface velocity sensor, solar power system, protective enclosure, cloud platform, SCADA integration or private-server data transmission.