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integrating sphereIntegrating Sphere

Gonio-photometer | Integrating sphere | Power analyzer | Spectro-radiometer

The integrating sphere is used to quickly measure the total light output of a lamp. The lamp being tested is placed in the center of the integrating sphere. At one side of the sphere is a light meter which measures the light output of the lamp. Between the lamp and the light meter there is a baffle to prevent the meter from seeing any direct light from the lamp.

The inside of the sphere (including the baffle) is coated with a very white paint that reflects all wavelengths equally. This allows us to get very accurate measurements. The light from the lamp bounces around the sphere until it reaches the light meter.

It is important that nothing else is in the sphere besides the lamp and the baffle. Anything else placed in the sphere, like a fixture, would absorb some of the light. So if anything besides the lamp and baffle is placed in the sphere, not all of the light reaches the light meter and this results in erroneous meter readings. This means that we can only obtain "bare lamp" readings in the sphere. The integrating sphere cannot measure the light output of the lamp in fixture (which the goniometer can).

The integrating sphere is also different from the gonio-photometer because the sphere only measures the total light output of a lamp and not the direction.

To the left is a picture of the equipment we use with the sphere. The light meter displays the light level being measured inside the sphere. We use the power meter to make sure we have the proper voltage and also to check the lamp's power usage. A ballast is necessary to run most non-incandescent lamps. The ballast cannot be in the sphere because it would interfere with the light reading. Finally, the connection box is needed to connect the ballast to the lamp inside the sphere and to the power supply.