LAI theory

In this section we shall explain as fully as we can how the SunScan computes its readings of leaf area index, and what the main limitations and provisos are in interpreting these for real canopies.

Ingredients of the LAI computation method

There are three broad areas contributing to the final result.

Geometric analysis

The first is the analysis of what happens to a ray of light passing through the canopy. In order to do this, we have to make some general assumptions about the canopy, i.e. uniformity, randomness and total absorption by canopy elements. This was done by Campbell (1986) for a beam of light from a single direction (the Direct solar beam) passing through a canopy with a generalised ellipsoidal leaf angle distribution function. This function allows a wide range of different canopy types to be described by the value of a single parameter ELADP.

Wood then integrated Campbell’s result over the whole sky to give a description of the transmission of Diffuse light through the same canopy. This is important because the transmission of Diffuse light is different, and in reality there is usually a combination of both Direct and Diffuse illumination. In particular, the analysis shows that Diffuse transmission is strongly dependent on the leaf angle distribution, a point which has not generally been recognised.

These functions are integrals which do not have direct analytical solutions, so have to be solved numerically, and computable functions fitted to the results. This has been done to a high degree of accuracy, improving on Campbell’s original approximation.

Incomplete absorption - more elaborate analysis

The above analysis based on black leaves is relatively straightforward. However, real leaves also reflect or scatter some of the light that falls on them. Typically, only about 85% of the incident light is absorbed. This means that in reality, every leaf element in the canopy is re-emitting light, as well as absorbing it, which makes the situation much more complicated.

Because the direction of any particular light ray can be changed by reflection or scattering, it means the spatial distribution of the light changes through the canopy. Therefore it is no longer adequate to consider just the vertical component of the light (as measured by a cosine corrected sensor), the horizontal component must also be included. This is why Wood’s analysis also considers a hemispherical response sensor (which measures both horizontal and vertical components).

The relentless advance of computing power has made it possible to model the situation in ways that were not feasible in the past. By integrating the "black leaf" analysis into a computer model Wood has calculated the light levels in the canopy across the whole range of canopy and incident light parameters.

54 • LAI theory

Document code: SS1-UM-1.05

Page 53 Page 55
Page 54
Image 54
Delta Electronics SS1-UM-1.05 user manual LAI theory, Ingredients of the LAI computation method
Page 53 Page 55

SS1-UM-1.05 specifications

Delta Electronics has long been recognized for its innovative solutions in power and thermal management technologies. One of its notable products is the SS1-UM-1.05, a compact and efficient power supply module designed to meet the needs of a variety of applications, from industrial automation to telecommunications.

The Delta SS1-UM-1.05 is a key component in the company’s extensive portfolio, providing reliable and stable power supply for both demanding and sensitive electronic equipment. One of the main features of this module is its high efficiency, which typically exceeds 90%. This not only minimizes energy consumption but also reduces heat generation, making it an ideal choice for applications where thermal management is crucial.

Another significant characteristic of the SS1-UM-1.05 is its wide input voltage range, which allows it to operate effectively in various environments. The module supports a voltage range from 90 to 264 VAC, ensuring consistent performance even in fluctuating supply conditions. This versatility makes it well-suited for global applications, accommodating different electrical standards and requirements.

The SS1-UM-1.05 also boasts a compact footprint, which is essential for space-constrained installations. Its design emphasizes not only performance but also ease of integration into existing systems. The module provides multiple output voltage options, allowing it to cater to specific power requirements, whether it be for industrial machinery or consumer electronics.

In terms of technologies, the SS1-UM-1.05 incorporates advanced power conversion technologies that enhance its overall performance. It features overload protection and thermal shutdown mechanisms to safeguard both the module and the equipment it powers from potential damages due to electrical faults. Moreover, it has low electromagnetic interference (EMI) emissions, which is crucial for environments sensitive to electrical noise.

The SS1-UM-1.05 is also designed with a robust enclosure that adheres to stringent safety and environmental standards. This enhances its durability and reliability, ensuring it can withstand harsh operating conditions. With these features, Delta Electronics demonstrates its commitment to delivering high-quality products that meet the evolving needs of industries worldwide.

Overall, the Delta SS1-UM-1.05 power supply module is an exemplary solution for those seeking a reliable, efficient, and compact power source. Its advanced features and technologies make it an indispensable component in modern electronic systems.
Top Page Image Contents