Haze meter measures light transmission and scattering in agricultural film.

Introduction

In agricultural production, the optical properties of covering materials directly affect the growth environment and yield of crops. Among them, light transmission and scattering characteristics are key parameters, which together determine the uniformity and intensity distribution of light. As an instrument that specifically measures the ratio of light transmittance to scattered light of materials, the haze meter provides a quantitative means for the evaluation of the optical properties of agricultural films. This article will systematically explain the working principle, testing method and application of haze meter in agricultural film detection.

Haze definition and principle

Haze refers to the ratio of scattered light flux to transmitted light flux that deviates from the direction of incidence greater than a certain angle when light passes through the material. It reflects the degree of light scattering inside or on the surface of the material due to crystallization, additives, micropores, and other factors. Light transmittance refers to the ratio of the light flux of the transmitted material to the incident light flux. Haze meters are usually based on the integrating sphere principle, which calculates the haze value by measuring the total transmitted light and the scattered light. The formula is expressed as follows:

Haze H = (T_d / T_t) × 100%

Among them, T_dis the scattered transmitted light flux, T_tis the total transmitted light flux. Light transmittance T = (T_t / T₀) × 100%，T₀This is the incident light flux.

Test Standards and Methods

Haze and light transmittance testing of agricultural films must follow relevant standards to ensure data comparability and accuracy. Common standards include international standards and national standards, which specify sample preparation, instrument calibration, test conditions and calculation methods. During testing, the film sample should be placed flat at the entrance of the integrating sphere to avoid wrinkles or contamination. The instrument emits a parallel beam of light to irradiate the sample, and the integrating sphere collects the transmitted light, and the total transmitted light and the scattered light are measured separately by the light detector.

Test conditions such as light source type (usually C light source or D65 light source), incidence angle, sample thickness, etc. need to be strictly consistent. Ambient temperature and humidity can also affect film performance, and it is recommended to operate in a standard laboratory environment.

Agricultural film application analysis

The haze and light transmittance of agricultural films have significant effects on their functions. High light transmittance films can maximize light intensity and promote photosynthesis; Appropriate haze can scatter direct light, reduce shadows, make the light distribution more even, and avoid local burns to crops. For example, leafy crops may benefit from higher haze for better light uniformity, while fruit crops may require high light transmittance to ensure energy accumulation.

Factors such as additives in the film, degree of aging, surface wear, etc. can alter its optical properties. Regular testing helps monitor film life, guide replacement timing, and optimize planting benefits.

Data interpretation and cases

Haze meter test results are typically presented as numerical formats, combined with light transmittance data, to provide a comprehensive assessment of film properties. Here is an example data sheet showing typical test ranges for different types of agricultural films:

In practical applications, appropriate parameters need to be selected according to planting needs. For example, in areas with strong light, the use of films with medium light transmittance and high haze may help improve the microclimate. In low-light environments, high-transmittance films are more suitable.

Technical considerations

When using haze metering, it is necessary to pay attention to regular calibration of the instrument to ensure that the stability of the light source is consistent with the reflectance of the inner wall of the integrating sphere. Samples should be clean and free of scratches and can be balanced in a standard environment before testing to reduce errors. For colored or patterned films, the effect of color absorption on light transmittance should be considered, and spectral analysis should be supplemented if necessary. Data interpretation should be based on the actual use environment of the film, and laboratory test conditions may differ from field conditions.

Epilogue

Haze meters provide an objective and repeatable measurement method for the optical properties of agricultural films. By quantifying light transmission and scattering characteristics, producers and farmers can select or develop suitable films based on crop needs to improve light energy efficiency. As material technology advances, haze meters will continue to play an important role in the research and development and quality control of agricultural cover materials.

References

1. International Illumination Commission Relevant Standards, Light Transmission and Scattering Measurement Methods.
2. National Standard for Optical Properties Test of Agricultural Covering Materials, Technical Specifications.
3. Research on optical properties of materials, journal articles, application of scattering theory in thin films.
4. Summary of integrating sphere measurement technology, chapter of instrument analysis manual.