Determination of basis weight of a material web using a microwave sensor, whereby the distance between the material web and the surfaces of the microwave sensor is being adjusted to a constant value by air cushions

摘要

A device for determining the weight per unit area of a moving material web, in particular a fibrous material web includes at least one microwave sensor that has an element for coupling the microwaves and a reference element. The coupling element and the reference element are located at a distance from one another in such a way that the material web can be moved therebetween. At least one microwave sensor element, the coupling element and/or the reference element can be moved such that the distances between the material web and the elements can be adjusted for or during the measurement of the moving material web.

主权项

1. A device to determine a basis weight of a moving material web, said device comprising:
at least one microwave sensor having a coupling element configured for coupling microwaves and a reference element, said coupling element and said reference element located at a distance from each other so that the material web passes therebetween, said coupling element and said reference element being moveable such that a distance between the material web and each of said coupling element and said reference element is adjustable and at least said distance between said material web and said reference element is set to a minimum value for or during measurement of the moving material web.