OTHER FLOW METERS Flow DetectorsOTHER FLOW METERSTwo other types of mechanical flow meters which can be used are the area flowand displacement meters. In addition, there exists much more sophisticatedtechniques for measurement of flow rate than use of differential pressure devices,such as anemometry, magnetic, and ultrasonic.EO 1.3 DESCRIBE the following types of mechanical flowdetectors, including the basic construction and theory ofoperation.a. Rotameterb. Nutating DiskAreaFlowMeterThe head causing the flow through an area meter is relatively constant such that the rate of flowis directly proportional to the metering area. The variation in area is produced by the rise andfall of a floating element. This type of flow meter must be mounted so that the floating elementmoves vertically and friction is minimal.RotameterThe rotameter, illustrated in Figure 6, is an area flowFigure 6 Rotametermeter so named because a rotating float is theindicating element.The rotameter consists of a metal float and a conicalglass tube, constructed such that the diameterincreases with height. When there is no fluid passingthrough the rotameter, the float rests at the bottom ofthe tube. As fluid enters the tube, the higher densityof the float will cause the float to remain on thebottom. The space between the float and the tubeallows for flow past the float. As flow increases inthe tube, the pressure drop increases. When thepressure drop is sufficient, the float will rise toindicate the amount of flow. The higher the flowrate the greater the pressure drop. The higher thepressure drop the farther up the tube the float rises.IC-04 Page 8 Rev. 0