NBL-W-PARS Photosynthetically Active Radiation (PAR) Sensor

The NiuBoL NBL-W-PARS Photosynthetically Active Radiation Sensor is designed to measure plant-usable light within the 400–700 nm PAR spectral range. It is suitable for greenhouses, farms, plant-growth research, agricultural meteorology, controlled-environment agriculture and weather monitoring systems.

The sensor uses a silicon photodetector together with an optical filter to respond to radiation within the photosynthetically active wavelength range. A cosine-corrected sensing surface helps account for light arriving from different angles.

The NBL-W-PARS is available with RS485 Modbus, 0–5 V and 0–2.5 V outputs, allowing integration with greenhouse controllers, PLCs, data loggers, agricultural IoT gateways and automatic weather stations.

NBL-W-PARS PAR Sensor Technical Specifications

Unit note: PAR can be represented using radiometric units such as W/m² or photon-based units such as μmol·m⁻²·s⁻¹. The current NBL-W-PARS product documentation includes both a W/m² measuring-range specification and a photon-flux sensitivity coefficient. Use the output unit and calibration coefficient supplied with the ordered sensor when configuring the data logger.

What Does a PAR Sensor Measure?

Photosynthetically active radiation refers to light within approximately 400–700 nm, the wavelength range commonly associated with plant photosynthesis.

A PAR sensor measures the light available within the photosynthetically active spectral range. It does not directly measure photosynthesis, crop growth rate or plant health. Those outcomes also depend on temperature, humidity, CO₂, water availability, nutrients, crop species and growth stage.

PAR Sensor vs Solar Radiation Sensor

Choose a PAR sensor when the project is focused on plant-usable light. Choose a pyranometer when the objective is broadband solar radiation, meteorological energy balance or solar-energy monitoring.

How the NBL-W-PARS PAR Sensor Works

The NBL-W-PARS uses a silicon photodetector combined with a spectral filter. The filter limits the sensor response primarily to the 400–700 nm photosynthetically active range.

Why Cosine Response Matters for PAR Measurement

Light in a greenhouse or outdoor crop canopy does not always arrive perpendicular to the sensor surface. The sun moves throughout the day, and diffuse sky radiation or artificial grow lights may reach the sensing surface from different directions.

A cosine-corrected sensor is designed so its response changes appropriately with the angle of incoming light. The NBL-W-PARS specifies cosine correction up to approximately an 80° incidence angle.

Correct PAR Sensor Installation

PAR Monitoring in Greenhouses

In greenhouse applications, PAR measurement can help quantify the amount of plant-usable light reaching the crop and compare changes caused by weather, glazing, shade curtains and supplemental lighting.

PAR Sensor and Daily Light Integral (DLI)

When PAR is recorded as photosynthetic photon flux density over time, the data can be integrated to calculate Daily Light Integral (DLI), which represents the total number of photosynthetically active photons received by a surface during one day.

DLI is typically expressed in:

mol·m⁻²·day⁻¹

The sensor itself provides the instantaneous light measurement. DLI calculation is performed by a data logger, controller or software using the time-series measurements.

RS485 Modbus or Voltage Output?

Using NBL-W-PARS in an Agricultural IoT System

NBL-W-PARS → RS485 / Voltage Input → Data Logger / PLC → 4G / Ethernet / LoRaWAN → Cloud or Private Server

The PAR sensor does not directly connect to the Internet by itself. Remote monitoring requires a compatible data logger or gateway to collect the sensor signal and transmit the data using the communication method selected for the project.

Local Display for PAR Measurement

For projects that do not require cloud communication, the analog-output version can also be connected to a compatible local digital display or controller.

Typical NBL-W-PARS Applications

Maintenance and Measurement Quality

NBL-W-PARS PAR Sensor FAQ

Q1. What does the NBL-W-PARS measure?

A1. It measures photosynthetically active radiation within the 400–700 nm wavelength range used for plant-light monitoring.

Q2. Is a PAR sensor the same as a pyranometer?

A2. No. A PAR sensor focuses on the 400–700 nm photosynthetically active range, while a pyranometer normally measures a wider broadband solar-radiation spectrum.

Q3. Is PAR the same as PPFD?

A3. PAR describes the photosynthetically active spectral region. PPFD describes the number of photons in that region reaching a unit area per second and is commonly expressed in μmol·m⁻²·s⁻¹.

Q4. Can the NBL-W-PARS measure greenhouse grow lights?

A4. It can be used to monitor light within its 400–700 nm response range from natural or artificial plant-light sources. Measurement suitability should be evaluated according to the spectral characteristics of the light source.

Q5. Does the sensor support RS485 Modbus?

A5. Yes. An RS485 version is available for connection to compatible PLCs, greenhouse controllers, data loggers and IoT gateways.

Q6. What voltage outputs are available?

A6. The documented output options include 0–5 V and 0–2.5 V in addition to RS485.

Q7. Does a high PAR reading mean the plants are photosynthesizing faster?

A7. Not necessarily. The sensor measures light availability. Actual photosynthesis also depends on crop species, CO₂ concentration, temperature, humidity, water availability, nutrients and plant condition.

Q8. Can PAR data be used to calculate DLI?

A8. Yes, when the system records photon-flux-based PAR measurements at known time intervals. The data logger or software can integrate these readings over the day to calculate DLI.

Q9. Can the sensor be used outdoors?

A9. Yes. The sensor is designed for continuous environmental monitoring when installed correctly and the sensing surface is kept clean and unobstructed.

Q10. Can PAR data be sent to our own server?

A10. Yes. The RS485 sensor can connect to a compatible data logger or IoT gateway, which can forward the measurements to a cloud platform or private server using supported communication protocols.

NBL-W-PARS PAR Sensor Datasheet

NBL-W-PARS-RAR-SENSOR-User-Manual.pdf

NBL-W-PARS for Greenhouse and Plant-Light Monitoring

The NBL-W-PARS PAR Sensor provides 400–700 nm plant-light measurement for greenhouse cultivation, crop research, agricultural meteorology and controlled-environment monitoring. RS485 and voltage-output options allow integration with greenhouse controllers, weather stations, PLC and agricultural IoT systems.

For quotation and model selection, specify the required output signal, power supply, cable length, indoor or outdoor installation, light source, quantity and the data logger or controller that will receive the PAR measurements.