A Novel Approach to Obtain PAR with a Multi-Channel Spectral Microsensor, Suitable for Sensor Node Integration.

Area of Science:

• Plant science and remote sensing.
• Optical sensor technology.

Background:

• Accurate measurement of photosynthetically active radiation (PAR) is crucial for understanding plant growth and optimizing agricultural practices.
• Existing PAR sensors can be expensive and bulky, limiting widespread deployment.

Purpose of the Study:

• To develop and validate an inexpensive, compact multi-channel spectrometer for measuring PAR.
• To assess the sensor's accuracy and its capability for retrieving additional light quality information.
• To demonstrate the sensor's integration into a wireless system for long-term field monitoring.

Main Methods:

• Utilized an eight-channel spectrometer sensor (AS7341) with integrated optical filters and an analog-to-digital converter.
• Developed a calibration method for accurate PAR measurements.
• Integrated the sensor into a solar-powered wireless sensor node.
• Performed exemplary field measurements.

Main Results:

• The developed sensor accurately derives PAR with an accuracy of 14 µmol/m²/s.
• The sensor architecture allows for retrieval of additional light quality information, expressed as the Relative Light Quality Index (RLQI).
• Successful integration into a solar-powered wireless sensor node enables high-density, long-term field experiments.

Conclusions:

• The proposed spectrometer offers a cost-effective and accurate solution for PAR measurement.
• The sensor's ability to provide light quality data enhances its utility for ecological and agricultural research.
• The wireless sensor node facilitates scalable, long-term environmental monitoring for applications like Gross Primary Production (GPP) estimation.