Choosing the right sphere size
Choosing the Right Sphere Size
The integrating sphere-based measurement system you choose will depend on several factors including wavelength range, accuracy, and repeatability. One of the more important choices is the sphere size.
There are several rules of thumb for choosing sphere size. The primary one is based on the maximum size of the radiation source you will measure. The size of the source is important, not just to ensure that it will fit in the sphere, but that the sphere is designed to properly baffle the source to ensure accurate measurement.
Ideally the sphere diameter will be three times the size of the source to be tested. This can be modified somewhat for longer fluorescent tubes and full luminaire assemblies.
The larger the integrating sphere, the greater the attenuation of energy. Choose a sphere that is large enough to accept the largest sources you plan to test but no larger.
Look at the specifications in the sphere section to determine which lamps will fit specific spheres.