With our variable area flowmeters (rotameters), you may adjust our sampling devices to the volume flow required. Our variable area flow meters (rotameters) are suitable for flow measurement of gases (air). They have a conical glass measuring tube with a vertically with a rotating float that is rotating freely. When selecting the appropriate rotameter, it is advisable to select the flow range of the rotameter so that the desired volumetric flow is ideally in the middle measuring range of the scale of the rotameter. The volume flow (flow rate) is shown at the upper edge of the float on the scale of the measuring tube. The gas must flow from bottom to top through the float flowmeter.