Flow measurement is accomplished by a transmitter programmed to convert a level reading into units of volume per time, as liquid passes through a flume or weir in an open channel. A flume is a specially shaped portion of the open channel, with an area or slope that is different from the channel’s slope or area. A weir resembles a dam placed across an open channel positioned so that liquid can flow over it.
Measurement devices are configured according to the geometry of the flume or weir. Devices must provide reliable measurement despite turbulence, solids content, corrosive chemicals, or varying flow velocities and flow depths. Environmental requirements often mandate the use of a totalizer and data logger.