Water meters are important for utility companies who need to accurately bill their customers for water used, but also make it possible for those customers to monitor and alter usage as needed. There are two different meter applications: positive displacement meters and velocity meters. Of these two there are a variety of types used. Positive displacement meters work by rapidly filling and emptying a chamber, and velocity by measuring the speed of water through the meter.
A type of positive displacement meter, these water meters have a small chamber containing a round disc that rests atop a spindle. The disc wobbles as the chamber fills with a defined volume of water. This motion is registered and records the water passing through the meter.
The second displacement type is piston meters, which use a piston that moves back and forth during water flow into the meter. Again, a known volume is measured with each movement allowing flow to be recorded for billing.
Turbine and propeller meters are velocity meters and record water use by measuring the speed of the water. Inside this type of water meter is a small rotating object that is turned by the flow of water. The number of revolutions by that gear is recorded to determine billing.
Venturi velocity meters use differing sized pipes to adjust the water pressure inside the unit. As the water flows, the change in pressure is measured to accurately judge the volume as it moves through the system and is squeezed through the smaller diameter pipes.
Orifice velocity metes are fundamentally similar to Venturi meters, except that orifice meters measure the pressure coming through a small hole in a circular disc at the end of the compression pipe. This difference in pressure is then recorded.
Ultrasonic velocity meters transmit sound waves across water flowing through a pipe. As the sound moves across the water it disrupts the velocity where a reading is taken to record changes in flow rate and then compared to a baseline to get a proper reading.
Magnetic meters use an insulated pipe for water flow. As water travels through the pipe, the flow creates a slight electrical current that is measurable against velocity to determine and record the rate.