A device for separation of fluid, in particular oil, gas and water, in connection with the extraction of such a fluid from formations under the surface of the earth or the sea bed. A product is determined of the actual average count value and a multiplying correction factor. The imaging apparatus also includes an ultrasound transducer that is configured to direct ultrasound waves through the imaging volume such that electromagnetic radiation passing through the imaging volume is modulated at the frequency of the ultrasound waves. Rollers within the surface of the rotatably driven to advance the lowermost sheet beneath the gate to the take-up mechanism. Embodiments of the device can be usable for methods of waterproofing andor roofing.