Primer on Technologies
Electromagnetic flow meters use electromagnetic induction to determine flow rate. They are based on Faraday’s Law, a basic law of electromagnetism that indicates how a magnetic field will react with an electric circuit to create an electromagnetic flow. (Faraday applied this technique to gauge the flow velocity of the River Thames, measuring induced voltage in the river by the earth’s magnetic field.) They work by creating a magnetic field perpendicular to the flow of water. As water flows across this field, it generates voltage. The voltage is measured by electrodes. Higher water flow equals more voltage. The flow meter can swap the poles on the magnetic field for improved accuracy.
Badger Meter’s M-Series, Neptune’s TRU/MAG, Sensus’ iPERL and accuMAG meters use electromagnetic flow technology.
In a fluidic oscillator, the meter body induces oscillations within the flow of water. For illustration, think of the oscillations as a pendulum swinging back and forth. As the flow rate increases, the pendulum swings back and forth more quickly. The number of oscillations is measured by electrodes, which in turn calculate consumption.
Fluidic oscillator technology is used in Elster AMCO’s SM700
Ultrasonic water meters operate by comparing how much time it takes for two ultrasonic pulses — one with the flow, the other counter to flow — to span a fixed distance between transducers. These data are plugged into a formula that yields average fluid velocity, and in turn, flow.
Ultrasonic technology is used in Badger Meter’s E-Series , Kamstrup’s FlowIQ and Master Meter’s Octave Ultrasonic.
Meters using any of these technologies maintain high accuracy across a wide range of flow rates and aren’t subject to the wear-related degradation of their mechanical counterparts.