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Integrating spheres measure reflectance and transmittance factors, commonly called

reflectance and transmittance. The relative spectral reflectance (transmittance) is

defined as the ratio of the flux reflected (transmitted) by the specimen to that of a

standard surface under identical geometrical and spectral conditions. For

transmittance the standard surface is air, and for reflectance the standard surface is a

secondary white standard calibrated relative to the perfectly reflecting diffuser.

Because of the geometry of the integrating sphere, it has the ability to collect most

reflected or transmitted radiation, remove any directional preferences, and present an

integrated signal to the detector.

Reflectance measurements

First, a baseline is recorded with the PTFE reference disk covering the reflectance

port. The sample is then mounted over the port and the reflection off the sample

surface is collected by the sphere. The reflectance is therefore measured relative to the

PTFE disk. This is the 'substitution' method.

The total (diffuse and specular) or the diffuse-only reflectance may be measured by

mounting the sample against the sphere port in two different configurations. The

specular component may be calculated from the difference of these two, or the Cary

Absolute Specular Reflectance Accessory (SRA P/N 00 100438 00) may be used to

give an absolute value of the specular component.

A variety of sample types and sizes may be used with the accessory, in conjunction

with different sample holders. For powders, pastes or other material requiring a

sample container, a powder cell is available for use in the DRA.

If only very small amounts of powder or paste are available, or if measurements

extending beyond the range of 250–2500 nm are required, the DRA cannot be used.

The 'Praying Mantis' accessory (P/N 00 100469 00) is used for these measurements.

Alternatively, you can use the powder cell

in conjunction with the small sample

holder.

Transmittance measurements

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Mantis 5000 Specifiche Pagina 4