Benoist Chromoradiometer

BENOIST CHROMORADIOMETER (Benoist), is an early qualimetric device in radiology, consisting of two different metals. It has the form of a circle, in the center of which is placed a round silver plate with a thickness of 0.11 mm; around it are arranged twelve aluminum plates with thicknesses from 1 to 12 mm. In its construction, Benoist utilized the property of a silver plate 0.11 mm thick to equally pass X-rays of different quality, while the permeability of an aluminum plate for rays of different quality depends on the thickness of the plate. On the fluorescent screen, behind which this device is placed, appears the glow from the silver circle and the aluminum plates. The thickness of that aluminum plate which will glow equally with the silver circle indicates the quality of the rays; it is expressed by numbers from 1 to 12 Be. The inconvenience of this device is that the thickness of the aluminum plates changes in steps, and therefore it was superseded by Venelt's cryptoradiometer (see) with a gradually thickening wedge.