Beta gauges

Measuring basis weight, thickness & density with beta transmission sensors

Beta transmission is the most common principle for gauging basis weight, and suitable for almost every application. It is often used for coating & converting processes in textile finishing, nonwovens, film extrusion, sheet extrusion, calendering processes and on other coated materials. Precise measurements on moving webs are the result of using extremely efficient beta radiation detectors. Depending on the requirements, different isotopes are available for different applications.

Principle of beta transmission

The intensity of beta rays is weakened according to the mass of the penetrated layer. Some beta particles get through the material, some particles are stopped. This weakening allows gauging the basis weight of nearly all materials. Different isotopes (Krypton, Strontium, Promethium) are used for different weight ranges. In coating processes, several beta gauges can be used to record the application quantity as a difference in weight.

Except for very low weight ranges, beta transmission is the universal method for measuring basis weight. However, certain radiation protection requirements must be complied with due to the weak radioactive isotopes. The density of the product web can also be determined by beta gauges in combination with thickness sensors. However, is the density of the measured product known and remains constant, the material thickness can also be determined via the basis weight by the beta gauge alone.


Gravimat FMI

Control of basis weight / thickness

Thomas Höpfl Mr Thomas Höpfl
+49 9441 601 121
thomas.hoepfl@mahlo.com

Transmission of beta rays

The weight monitoring and control system measures the weight continuously, without contact, destruction-free and on moving product. The measurement is based on the attenuation of rays from a radioactive isotope through the substrate located in the measuring gap. This attenuation in intensity is an indication of the weight of the product.

Product Highlights

  • Highest repeatability ofthe measured values
  • Non-contacting measurement
  • Digital signal processingTemperature compensation
  • Source ageing compensation
  • Gap compensation

Customer benefits

  • Material saving
  • Quality assurance
  • Increased production
  • Comprehensive quality documentation

SpecificationValueUnit
IsotopeKrypton-85 (Kr-85)Strontium-90 (Sr-90) 
Activity3,0 / 9,620,5GBq
Measuring range10 - 1400100 - 6000g/m²

  • Coating of textiles
  • Carpet coating

With the common basis weight measurement is based on the attenuation of radioactive rays through the substrate located in the measuring gap. This attenuation in intensity is an indication of the weight of the product. The basis weight is hereby determined without contact and continuously at high accuracy.

For very different weight ranges, such as pile carpeting or coated textile bases, different nuclides are available. Differential measurements with two measuring points are  normally made to control a coating process. The coating weight is continuously recorded in the process and the application or coating unit of the machine is automatically adjusted. This allows immediately responding even to short frequency  changes of the incoming basis weight.

The coating weight is continuously recorded in the process and the application or coating unit of the system is automatically readjusted. In this way, even short-frequency changes in the incoming basis weight are reacted to immediately.

  • Krypton-85
  • Strontium 90
  • Gap cleaning

  • Module of the process control Optipac VMC-15
  • Stand-alone device

Documents