Know the Flow: Non-Contact Magnetic Flow Rate Sensing for Water Meters

Positive displacement water meters are found throughout the world's water distribution networks to totalize water consumption. Containing internal permanent magnets, the water meters are underutilized sensors. Flow data from these meter locations can be used to non-intrusively identify the operation of individual water loads from an aggregate data stream at the meter. This article models these meters as nonideal magnetic encoders and presents a methodology for inexpensively retrofitting these meters with digital flow rate measurement capabilities, effectively bringing them into the growing body of smart metering devices and non-intrusive load monitoring without any contact with the water passing through them. We present a model of the magnetic field produced by these meters, discuss associated magnetic sensing hardware, and describe compensation, flow rate estimation, and post-processing algorithms for flow rate extraction. Verification is provided with experimental results.