Technical Specifications and Measurement Accuracy Analysis of Photosynthetically active radiometer

Photosynthetically active radiometer is used to measure photosynthetically active radiation (PAR) in the 400-700 nm wavelength range. It employs a silicon photodetector and optical filters, outputting a voltage signal proportional to the incident radiation. This instrument conforms to the national standard GB/T 35139-2017 and is widely used in agricultural meteorology and crop growth research.

Photosynthetically active radiometer is a specialized instrument for measuring PAR in the 400-700 nm wavelength range of natural light. This wavelength band is the core spectral region required for photosynthesis in green plants, and PAR is the energy source for plant life activities, organic matter synthesis, and yield formation. Photosynthetically active radiometer uses a silicon photodetector as its core sensing element, combined with a 400-700 nm optical filter for spectral selection. When there is light, the detector generates a voltage signal proportional to the incident radiation intensity, and its sensitivity is proportional to the cosine of the incident light's angle of incidence. Each instrument is calibrated with its own sensitivity coefficient and can directly output measurement values in μmol·m⁻²·s⁻¹.

The technical specifications of Photosynthetically active radiometer determine its measurement performance and applicable scenarios. It uses a DC 12V power supply, with an operating current of only 3mA and a power consumption of 0.036W, classifying it as a low-power device. The operating temperature range is -20 to 65℃, and the communication interface uses the RS485 standard interface with a minimum data interval of 0.5 seconds. Regarding sensor parameters, the photosynthetically active radiation measurement range is 0 to 2000 W/m², with a resolution of 1 W/m² and an accuracy better than ±3%. The photosynthetic photon flux density measurement range is 0 to 9200 μmol·m⁻²·s⁻¹, also possessing a resolution of 1 and an accuracy better than ±3%. The response time is no more than 10 seconds, the annual stability is better than ±3%, and the zero-point drift is no more than 10 W/m². The measurement spectral range is 400 to 700 nanometers, covering the effective wavelengths required for plant photosynthesis.

The Photosynthetically active radiometer is designed for all-weather use. The body is machined from cast bronze and treated with electrostatic powder coating for excellent corrosion resistance. The hemispherical quartz glass cover is cold-worked and ground to a thickness of 1.5 ± 0.1 mm, with a concentricity deviation of no more than 0.05 mm and a spectral transmittance of over 90%. O-rings are installed at all connections, and a desiccant is included inside to ensure normal operation in humid environments.

The Photosynthetically active radiometer has wide applications in agricultural meteorology, crop growth research, photosynthetic potential research, greenhouse control, ecology, and solar energy research. The Photosynthetically active radiometer has been incorporated into the national standard system; GB/T 35139-2017 "Photosynthetically active radiometer" is under the jurisdiction of the National Technical Committee for Standardization of Meteorological Instruments and Observation Methods, and the competent authority is the China Meteorological Administration. The implementation of standards provides a unified technical basis for product design, production and inspection.