Net Radiation Sensor with RS485 for Climate Monitoring

The JW-TBB-1L(LC26) Net Radiation Sensor is a professional thermopile instrument designed to measure the balance between downward and upward radiation above a surface.

It detects both shortwave and longwave radiation across a broad spectral range from 0.28 to 50 μm. By measuring the difference between incoming and outgoing radiation, the sensor provides net radiation data for surface energy balance studies, evapotranspiration analysis, irrigation research, climate monitoring and ecological observation.

An optional integrated RS485 output module allows the sensor to connect directly to compatible data loggers, RTUs, weather station controllers and environmental monitoring systems. This reduces the need for a separate signal converter and simplifies field wiring.

The sensor is suitable for agricultural weather stations, research fields, meteorological observation networks, hydrological monitoring projects and long-term environmental studies.

Contact JW-IoT or send your project requirements through WhatsApp for model selection, communication integration and weather station configuration support.

Product Overview

Net radiation is one of the main components of the surface energy balance. It represents the amount of radiation energy remaining at a surface after incoming and outgoing radiation have been considered.

The JW-TBB-1L(LC26) measures radiation from both the upper and lower directions. Its upward-facing sensing surface detects radiation received from the sky, while its downward-facing sensing surface detects radiation leaving or being reflected by the ground, crop canopy, water surface or other monitored surface.

The difference between these two directional measurements is reported as net radiation.

This information is widely used to understand how radiation energy is exchanged between the atmosphere and the monitored surface. It can support research into crop water demand, evapotranspiration, soil heat exchange, microclimate variation and environmental change.

JW-IoT supplies a wider range of radiation sensors for total solar radiation, net radiation, ultraviolet radiation, PAR, longwave radiation and spectral irradiance monitoring.

What Is Net Radiation?

Net radiation is the difference between all incoming radiation and all outgoing radiation at a surface.

In general terms:

Net Radiation = Incoming Radiation − Outgoing Radiation

Incoming radiation may include:

• Direct and diffuse shortwave solar radiation
• Downward longwave radiation emitted by the atmosphere and clouds

Outgoing radiation may include:

• Shortwave solar radiation reflected by the surface
• Longwave thermal radiation emitted by the ground, vegetation, water or other surfaces

During sunny daytime conditions, net radiation is often positive because the surface receives more radiation than it releases.

At night, net radiation may become negative because there is no incoming solar radiation and the surface continues to emit longwave thermal radiation.

The actual value depends on solar elevation, cloud cover, surface temperature, surface reflectivity, vegetation, soil moisture and local weather conditions.

Why Measure Net Radiation?

Net radiation helps researchers and monitoring-system operators determine how much radiant energy is available at the land, crop or water surface.

This energy influences:

• Evaporation
• Plant transpiration
• Soil heat flux
• Surface temperature
• Atmospheric heat exchange
• Crop water demand
• Local microclimate
• Ecosystem energy balance

Unlike a standard solar radiation sensor that measures only radiation arriving from above, a net radiation sensor considers radiation exchange in both directions.

This makes it particularly useful for agricultural water studies, evapotranspiration research and surface energy balance analysis.

Working Principle

The JW-TBB-1L(LC26) uses thermopile sensing technology.

Radiation absorbed by the upper and lower sensing surfaces creates a temperature difference inside the sensor. The thermopile converts this temperature difference into a small electrical signal.

The polarity and magnitude of the signal depend on the direction and amount of net radiation.

When incoming radiation is greater than outgoing radiation, the sensor normally produces a signal representing positive net radiation.

When outgoing radiation is greater than incoming radiation, such as during certain nighttime conditions, the measured net radiation may be negative.

The raw sensor sensitivity is specified as 7–14 μV/(W/m²). In the optional RS485 version, the internal signal-conversion module processes the sensor output and transmits digital measurement data to a compatible receiving system.

Technical Specifications

Specifications may vary according to the selected output and project configuration. Confirm the power supply, communication protocol, cable length, register map, connector type and mounting accessories before ordering.

RS485 Output and System Integration

The net radiation sensor can be configured with an integrated RS485 output module.

The integrated module converts the sensor signal into a digital output that can be transmitted directly to a compatible monitoring device. This design can reduce external signal-conversion components and simplify field installation.

The RS485 version may be integrated with:

• Weather station data loggers
• Agricultural monitoring controllers
• Environmental RTUs
• Industrial data acquisition units
• IoT gateways
• PLC-based monitoring systems
• Research data acquisition systems
• Local or cloud monitoring platforms

RS485 is well suited to multi-sensor field networks because several compatible devices can share the same communication bus when the system is designed and addressed correctly.

Before ordering, confirm the following integration details with JW-IoT:

• Required communication protocol
• Modbus register map
• Baud rate
• Device address
• Data format
• Power supply
• Cable length
• Cable and wire definition
• Data logger model
• Number of sensors on the bus
• Required sampling interval
• Cloud or API integration requirements

JW-IoT can also supply the sensor as part of a complete weather station with a data logger, communication module, solar power supply, mounting structure and cloud platform.

Main Applications

Agricultural Weather Stations

Net radiation data can help researchers understand the energy available above a crop canopy.

It can be combined with air temperature, relative humidity, wind speed, rainfall, soil moisture and soil heat flux data to support agricultural climate studies.

Typical applications include:

• Crop microclimate monitoring
• Field energy balance observation
• Irrigation research
• Crop water-use studies
• Drought-response experiments
• Agricultural meteorological stations

Evapotranspiration Research

Net radiation is an important input in many evapotranspiration and surface energy balance studies.

It represents a major source of energy for evaporation from soil and water surfaces and transpiration from plants.

For research-grade evapotranspiration projects, net radiation should be evaluated together with other parameters such as:

• Air temperature
• Relative humidity
• Wind speed
• Soil heat flux
• Atmospheric pressure
• Crop or surface characteristics

The sensor provides one important measurement component, but it does not calculate complete evapotranspiration independently.

Irrigation Management Studies

Net radiation data can improve understanding of changing crop water demand under different weather and field conditions.

It may support:

• Irrigation scheduling research
• Comparison of irrigation treatments
• Soil-water balance studies
• Crop stress analysis
• Water-use efficiency experiments
• Precision agriculture research

For operational irrigation control, net radiation data is usually combined with soil moisture sensors, weather data and crop-specific management models.

Climate and Microclimate Monitoring

The sensor can be installed at climate and microclimate monitoring sites to observe radiation energy exchange between the surface and atmosphere.

Possible deployment locations include:

• Agricultural fields
• Grasslands
• Forest research sites
• Wetlands
• Deserts
• Urban surfaces
• Green roofs
• Watersheds
• Coastal observation sites

Long-term net radiation records can help researchers compare seasonal and environmental changes.

Surface Energy Balance Studies

The surface energy balance describes how net radiation is distributed into different energy-transfer processes.

Depending on the research method, these may include:

• Sensible heat flux
• Latent heat flux
• Soil heat flux
• Heat storage
• Other local energy exchanges

The net radiation sensor provides the radiation component required for this type of analysis.

Hydrological and Ecological Research

Net radiation influences evaporation, surface temperature and water exchange between land, vegetation and the atmosphere.

The sensor can support:

• Watershed research
• Wetland monitoring
• Lake and reservoir studies
• Ecosystem energy balance studies
• Forest hydrology
• Land-atmosphere interaction research
• Climate-change observation

Meteorological Observation Networks

The RS485 version can be integrated into automatic meteorological stations and distributed environmental monitoring networks.

It can operate alongside:

• Air temperature and humidity sensors
• Wind speed and direction sensors
• Rain gauges
• Atmospheric pressure sensors
• Soil temperature sensors
• Soil moisture sensors
• Surface temperature sensors
• Data loggers and telemetry units

Solar and Radiation Research

Net radiation is different from global solar irradiance, but it can provide additional information about the total radiation exchange at a monitored surface.

For projects that only need incoming global solar irradiance, a Class A Pyranometer or Total Solar Radiation Sensor Class B may be more appropriate.

Installation Guidelines

Correct installation is essential for reliable net radiation measurement.

Select a Representative Location

Install the sensor above a surface that represents the area being studied.

Avoid locations close to:

• Buildings
• Walls
• Trees
• Poles
• Large instruments
• Reflective metal surfaces
• Artificial heat sources
• Irrigation equipment that may spray the sensor

Nearby objects can block incoming radiation or create unwanted reflections.

Keep Both Sensing Surfaces Unobstructed

The upper sensing surface must have a clear view of the sky.

The lower sensing surface must have an unobstructed view of the monitored ground, crop canopy, water surface or other target surface.

Do not install a wide support plate directly under the sensor, because it may block the lower field of view.

Mount the Sensor Horizontally

For standard surface net radiation monitoring, mount the sensor level unless the research protocol requires another orientation.

Use the leveling mechanism or a suitable mounting bracket to check the sensor position.

Minimize Support-Arm Interference

The support arm should be narrow and positioned to minimize shadows and reflections.

Where practical, orient the mounting structure so that it produces the least possible interference during the main measurement period.

Select an Appropriate Height

The installation height should reflect the objective of the study and the size of the monitored surface.

The lower sensing surface observes an area that increases as installation height increases. Mounting too close to an uneven crop canopy or heterogeneous surface may reduce spatial representativeness.

Keep the installation method consistent throughout a comparative or long-term study.

Protect and Route the Cable Correctly

Secure the cable to the mounting arm without pulling on the sensor connector.

Use drip loops and weather-resistant cable protection where required. Keep communication cables away from high-voltage power lines and sources of strong electromagnetic interference.

Operation and Maintenance

Regular inspection helps maintain measurement reliability.

Recommended maintenance includes:

• Clean the upper and lower sensing surfaces carefully.
• Remove dust, pollen, bird droppings, water stains and other contamination.
• Do not scratch or damage the radiation-absorbing surfaces.
• Check that the sensor remains level.
• Inspect mounting screws and brackets.
• Check cable insulation and connectors.
• Confirm that the support arm has not shifted.
• Verify that vegetation has not grown into the sensor field of view.
• Check the RS485 communication status.
• Review data for sudden offsets, flat lines or unexplained changes.
• Follow the recommended calibration or verification schedule.

The inspection frequency should be increased in dusty, agricultural, coastal or high-pollution environments.

Net Radiation Sensor vs. Pyranometer

A net radiation sensor and a pyranometer measure different radiation parameters.

A pyranometer should be selected when the project primarily needs global solar irradiance.

A net radiation sensor should be selected when the project needs to understand the total radiation balance between the atmosphere and the monitored surface.

Net Radiation Sensor vs. Four-Component Net Radiometer

The JW-TBB-1L(LC26) provides a combined net radiation measurement.

A Four Component Net Radiometer separately measures four radiation components:

• Downward shortwave radiation
• Upward shortwave radiation
• Downward longwave radiation
• Upward longwave radiation

Choose the standard net radiation sensor when the main requirement is a combined net radiation value and simpler system integration.

Choose a four-component radiometer when the research requires separate analysis of shortwave and longwave radiation in both directions.

The four-component option is generally more suitable for advanced atmospheric research, land-surface energy balance studies and detailed scientific radiation analysis.

Net Radiation Sensor vs. Total Solar Radiation Sensor

A total solar radiation sensor measures incoming solar radiation from the upper hemisphere.

It does not directly subtract radiation reflected or emitted by the surface.

For general weather stations, solar irradiance monitoring and environmental radiation measurement, the Photoelectric Total Solar Radiation Sensor may be suitable.

For studies focused on surface energy gain and loss, the net radiation sensor provides the more relevant parameter.

How to Select the Correct Radiation Sensor

Before requesting a quotation, determine which radiation parameter the project requires.

Recommended Monitoring System Configuration

A complete net radiation monitoring station may include:

• JW-TBB-1L(LC26) net radiation sensor
• Air temperature and humidity sensor
• Wind speed and direction sensor
• Rain gauge
• Atmospheric pressure sensor
• Soil temperature sensor
• Soil moisture sensor
• Soil heat flux sensor
• Surface temperature sensor
• Data logger or RTU
• RS485 communication network
• 4G, LoRaWAN or other telemetry device
• Solar panel and battery
• Weather station mast and mounting arms
• Cloud platform or local data software

The final configuration should be based on the research method, site conditions, required sampling interval, communication coverage and power availability.

Why Choose JW-IoT?

JW-IoT supplies radiation sensors, weather instruments and sensor-to-cloud monitoring solutions for agriculture, meteorology, environmental observation, water management and industrial IoT projects.

Available project support includes:

• Radiation sensor selection
• RS485 communication integration
• Data logger and RTU matching
• Weather station system design
• Mounting bracket configuration
• Solar power system matching
• 4G and LoRaWAN communication options
• Cloud platform integration
• API and data interface support
• OEM and private-label cooperation
• Project documentation
• Remote technical support

System integrators, research organizations, distributors and project contractors can contact JW-IoT for customized monitoring configurations.

Ordering Information

Please provide the following information when requesting a quotation:

• Intended application
• Required measurement parameter
• Installation surface
• Installation height
• Required output signal
• RS485 protocol requirements
• Data logger or RTU model
• Required cable length
• Power supply
• Sampling interval
• Communication method
• Mounting accessory requirements
• Calibration or documentation requirements
• Order quantity
• OEM or private-label requirements
• Delivery destination

Contact JW-IoT for product selection, quotation and system integration support.