The measuring system is attached to the Swelltest die head by means of an adaptation kit. The distance to the die head can be adjusted between 12 and 50 mm. A red laser beam emitted from the laser diode in the transmitter is converged into a parallel beam by the transmitter lens. This parallel beam passes through the measuring area before it meets a CCD image sensor in the receiver.
During processing, the extrudate runs through the measuring sector. When the laser beam meets the extrudate, its cross-section is interrupted. This interruption projects a shadow with an area proportional to the diameter of the extrudate on the receiver. The one-dimensional CCD image sensor scans and calculates the shadow area from which
the sample dimensions are calculated by the controller.