There are two types of gravimetric blender.

Loss in weight

This type of gravimetric blender measures the "loss in weight" from two or more hoppers using a load cell under each hopper. Material is usually dispensed from the hoppers using a screw conveyor. All materials are dispensed together and the rate of dosing from each hopper is controlled to ensure the correct blend is achieved.

Gain in weight (sometimes called a batch blender)

A gain in weight gravimetric blender has two or more hoppers arranged above a weigh-pan. These hoppers contain the components which are to be mixed, at the base of each hopper there is a valve to control the dispensing of material from the component hopper into the weigh-pan. The components are dispensed one at a time into the weigh pan until the target or batch weight is reached. Once the batch has been weighed out the contents of the weigh-pan are dispensed into a mixing chamber where they are blended. The resulting mixture exits the base of the mixing chamber into the processing machine.

A typical application of a gravimetric blender would be mixing virgin plastic granules, recycled plastic, and masterbatch (an additive used to colour plastics) together.