The intensity of X-rays is weakened according to the mass of the penetrated layer. This weakening allows determining the basis weight of nearly all materials. Different high-voltage ranges are used for different weight ranges. No radiation protection precautions are required in Europe and many other countries for X-ray radiation energy less than 5 kV.
X-Ray transmission is very suitable for materials consisting only of a single component. The advantage compared to beta emitters is the emission of the X-ray tube that can be shut off.
The density of the product web can also be determined in combination with thickness sensors. If the density of the measured product is known, however, and remains constant, the material thickness can also be determined via the basis weight.
Measurement of basis weight (mass per unit area) / thickness
The sensor measures grammage and material thickness by means of X-Ray backscatter
Backscattering of X-rays
The weight monitoring and control system measures the weight continuously, without contact, destruction-free and on moving product. The X-ray radiation from an X-ray tube is directed towards the product, from which it is partially scattered back.
The greatest part of the radiation passes through the product and is absorbed by a beam dump or steel facing roller installed there. This backscattered portion is an indication of the weight of the product.
- Single-sided measurement requiring a minimum of space; easy to integrate into existing systems
- Measuring device works with an X-ray tube that can be turned off, and has no radioactive isotope emitter
- Insensitive to distancerelated variations due to patented detection system
- Can be installed without having to modify the processing range and existing web guiding arrangement
- Easy to certify, and a minimum of radiation safety requirements; X-rays can be turned off
- Highly accurate and virtually insensitive to product composition
The Gravimat FMX sensor consists of a compact X-ray tube and its high voltage supply as well as special modern X-ray detectors with the electronics for data acquisition. It is completely insensitive to environmental influences such as temperature and humidity. This new measuring principle with the proven components is used for data acquisition and processing by Mahlo and is therefore fully compatible with other products of the Qualiscan QMS family.
The way in which X-rays interact with mass allows the measurement of a very wide range of basis weights with only one sensor - from 50 - 20,000 g/m2 with the fabric on a counter roll or also free-floating!