Net Radiation Sensor with RS485 for Climate Monitoring

Description

The JW-TBB-1L(LC26) Net Radiation Sensor is a thermopile instrument designed to measure the balance between radiation received by a surface and radiation leaving that surface.

It measures both upward and downward radiation across a broad spectral response of 0.28–50 μm, allowing researchers to determine net radiation for applications such as:

• Surface energy balance studies
• Evapotranspiration research
• Agricultural climate monitoring
• Irrigation research
• Hydrological observation
• Ecological monitoring
• Meteorological research

An optional integrated RS485 output module allows the sensor to connect directly to compatible data loggers, RTUs, weather station controllers and environmental monitoring systems.

Unlike a conventional pyranometer that mainly measures incoming solar irradiance, the JW-TBB-1L(LC26) measures the difference between incoming and outgoing radiation, providing the radiation balance required for land-surface and atmosphere-energy studies.

For additional radiation monitoring products, browse:

Radiation Sensors

Product Overview

Net radiation describes the balance between radiation arriving at a monitored surface and radiation leaving it.

The JW-TBB-1L(LC26) measures radiation from two directions.

Its upper sensing surface receives radiation from the sky, while its lower sensing surface observes radiation leaving or being reflected by the monitored surface.

The monitored surface may include:

• Bare soil
• Crop canopy
• Grassland
• Water
• Wetland
• Forest surface
• Urban surface
• Other research surfaces

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

This measurement is especially important when the objective is not simply to know how much solar radiation is arriving, but to understand how much radiation energy remains available at the surface.

What Is Net Radiation?

In general terms:

Net Radiation = Incoming Radiation − Outgoing Radiation

Incoming radiation may include:

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

Outgoing radiation may include:

• Reflected shortwave solar radiation
• Longwave thermal radiation emitted by the monitored surface

During sunny daytime conditions, net radiation is often positive because incoming radiation exceeds outgoing radiation.

At night, net radiation may become negative because solar input disappears while the surface continues to emit longwave thermal radiation.

Actual net radiation depends on factors such as:

• Local weather conditions
• Solar elevation
• Cloud cover
• Surface temperature
• Surface reflectivity
• Vegetation
• Soil moisture

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.

How the JW-TBB-1L(LC26) Works

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

Radiation absorbed by the upper and lower sensing surfaces produces a temperature difference within the sensor.

The thermopile converts this temperature difference into an electrical signal.

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

In general:

• Incoming radiation greater than outgoing radiation → positive net radiation
• Outgoing radiation greater than incoming radiation → negative net radiation

The raw sensor sensitivity is specified as:

7–14 μV/(W/m²)

When the optional RS485 version is selected, the internal signal-conversion module converts the sensor output into digital measurement data for transmission 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.

Optional RS485 Output and System Integration

The JW-TBB-1L(LC26) can be configured with an integrated RS485 output module.

This option converts the sensor signal into digital data that can be transmitted directly to compatible monitoring equipment.

The RS485 version may be integrated with:

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

The integrated digital-output option can reduce the need for separate external signal conversion.

Before ordering an RS485 version, confirm:

• Required communication protocol
• Register map
• Baud rate
• Device address
• Data format
• Power supply
• Cable length
• Data logger model
• Required sampling interval

For multi-sensor projects, the complete communication architecture should be designed according to the receiving system and field-network requirements.

Main Applications

1. Agricultural Weather Stations

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

The sensor can be used together with measurements such as:

• Air temperature
• Relative humidity
• Wind speed
• Rainfall
• Soil moisture
• Soil heat flux

Typical research applications include:

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

2. Evapotranspiration Research

Net radiation is an important component in many evapotranspiration and surface-energy studies.

It represents a major radiation-energy input associated with:

• Soil evaporation
• Water-surface evaporation
• Plant transpiration

For research-grade evapotranspiration studies, net radiation is normally evaluated together with other parameters such as:

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

The JW-TBB-1L(LC26) provides the net radiation measurement component.

It does not independently calculate complete evapotranspiration.

3. Irrigation Research

Net radiation can help researchers study how available surface energy changes under different weather and crop conditions.

Possible applications include:

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

For operational irrigation management, net radiation should normally be combined with other environmental and soil measurements.

4. Climate and Microclimate Monitoring

The sensor can be used to observe radiation-energy exchange between the atmosphere and the monitored surface.

Possible research environments include:

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

Long-term datasets can support comparison of seasonal and environmental changes in surface radiation balance.

5. Surface Energy Balance Studies

The surface energy balance describes how available energy is distributed among different heat-transfer processes.

Depending on the research method, these can 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.

6. Hydrological and Ecological Research

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

Possible applications include:

• Watershed research
• Wetland monitoring
• Lake and reservoir studies
• Forest hydrology
• Ecosystem energy-balance studies
• Land-atmosphere interaction research
• Long-term climate observation

Net Radiation Sensor vs Pyranometer

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

Choose a pyranometer when the project primarily needs global solar irradiance.

Choose a net radiation sensor when the project needs to understand total radiation gain and loss at a monitored surface.

For high-quality global solar irradiance measurement, see:

Class A Pyranometer

Net Radiation Sensor vs Four-Component Net Radiometer

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

A four-component net radiometer separately measures:

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

Select a standard net radiation sensor when the project primarily needs one combined net radiation value.

Select a four-component system when the research requires independent analysis of the four directional shortwave and longwave components.

The latter is more suitable for detailed atmospheric or land-surface radiation research.

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 monitored surface.

For general weather-station irradiance monitoring, see:

Photoelectric Total Solar Radiation Sensor

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

Different radiation sensors are designed for different measurement objectives.

Related products:

Direct Solar Radiation Sensor

Near Infrared Radiation Sensor

Installation Guidelines

Correct installation is essential for representative net-radiation measurements.

1. Select a Representative Surface

Install the sensor above a surface that represents the research area.

Avoid installation close to objects such as:

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

Nearby objects can produce shading, obstruction or unwanted reflections.

2. Keep Both Sensing Surfaces Clear

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

The lower sensing surface should have an unobstructed view of the monitored surface.

Do not install a wide mounting plate directly under the sensor if it blocks the lower field of view.

3. Mount the Sensor Level

For standard surface net-radiation monitoring, install the sensor horizontally unless the research protocol requires another orientation.

Check the sensor position using the available leveling arrangement or suitable mounting structure.

4. Minimize Support-Arm Interference

Use a support arm that minimizes:

• Shadowing
• Reflection
• Obstruction of the lower field of view

The mounting structure should interfere as little as possible with the radiation environment being measured.

5. Select an Appropriate Installation Height

Installation height should match the research objective and monitored surface.

As the sensor is mounted higher, the lower sensing surface observes a larger area.

For heterogeneous surfaces or uneven crop canopies, mounting too close may reduce spatial representativeness.

Use a consistent installation method for long-term or comparative studies.

Operation and Maintenance

Recommended maintenance includes:

• Clean the upper and lower sensing surfaces
• Remove dust, pollen, water stains and other contamination
• Avoid scratching the sensing surfaces
• Check that the sensor remains level
• Inspect mounting hardware
• Check cable insulation and connectors
• Confirm that the support structure has not moved
• Prevent vegetation from obstructing the lower field of view
• Check RS485 communication when applicable
• Review data for unexpected offsets or flat readings
• Follow the required calibration or verification schedule

Inspection frequency should be increased in dusty, agricultural, coastal or polluted environments.

Typical Monitoring System

A research monitoring station may combine the JW-TBB-1L(LC26) with:

• Air temperature and humidity sensors
• Wind speed and direction sensors
• Rain gauge
• Atmospheric pressure sensor
• Soil temperature sensor
• Soil moisture sensor
• Soil heat flux sensor
• Surface temperature sensor
• Data logger or RTU

The final configuration should be selected according to:

• Research method
• Site conditions
• Sampling interval
• Communication requirement
• Power availability
• Data-acquisition system

Request a Net Radiation Sensor Configuration

Choosing a radiation sensor should begin with the measurement objective.

If your project requires:

• Combined incoming and outgoing radiation
• Surface energy balance data
• Evapotranspiration research
• Crop-energy studies
• Climate or ecological monitoring
• Optional RS485 system integration

the JW-TBB-1L(LC26) Net Radiation Sensor may be suitable.

Contact JW-IoT with your application, installation environment, output requirement, data logger and quantity for configuration support and quotation.