Other Methods of Measuring Flow
 

The two general categories of velocity meters are propeller and electromagnetic.  Propellers or water wheel devices are placed directly in the flow and as the flow increases the propeller turns more rapidly, thus causing the meter to show a proportional increase.  In an electromagnetic meter, the water is passed through a magnetic field and an electrical current is produced in the liquid.  The amount of electricity produced is directly proportional to the flow rate and the electrical variances can be used to measure flow.  Flow of an open channel or stream can be found by multiplying the velocity by the cross sectional area. The flow from an open pipe can be found by multiplying the cross sectional area of the pipe by the velocity of the water in feet per second.  Other ways of determining flow include observed temperature loss in pipe sections and mass flow meters.