A continuous density measurement of the fibre material delivered by the volumetric feeder to the card is made before the feed rollers by the emission of an isotopic ray. This is produced by either a radioactive source or by an X-ray generator and is past through the lap of fibres, over the complete width. The residual radiation is collected by a scintillation tube, which converts it into an electric signal that is inversely proportional to the density of the mass conveyed.

This signal, together with those received from Isolated Tacho Adapters monitoring the operation parameters of the card, is treated by a microprocessor which controls a variable speed motor driving the feed rollers, in order to obtain, at the output side, a perfectly stable quantity of fibres being fed to the card.

The Control Panel is the dialog modulus between the user and the machine. It displays all the parameters of operation and production.

The SL TESTER, diagnosis device is used to tests the equipment , but it can also maintain, in case of malfunction, the synchronism with the card while awaiting the replacement parts.