In the case of permanent material thickness, the density of a material is determined on the basis of the principle of radiation absorption (Figure 11.23). For this, the so — called mass-absorption coefficient (p) should be introduced (see Eq. (5.48)), with which:

— = exp(—ppl) (11.28)

І0

The material density measured by radiation absorption can be determined by solving Eq. (11.28) for (p) density. Other members of the equation are identical to the parameters found in Eq. (11.27).

Typical application fields of both thickness and density measurements are paper industry, metal sheet rolling, and plastic foil production as well as measuring and

Figure 11.23 Material density determination based on radiation absorption.

continuous monitoring of the thickness of textiles, glass sheets, and laminated wooden sheets.

Industrial examples for the application of density measuring systems are:

• Density measurement of a streaming medium (such as crude oil, benzin, or petrol) in oil pipelines.

• Monitoring of chemical technology processes by measuring material density.

• Monitoring of efficiency in grinding machines by measuring the density of powder.

• Continuous monitoring of the density of materials transported on conveyors.