Installed meter   Remote Mount

Although the full-bore magnetic flow meters used are more expensive than conventional flow meters (such as paddle wheel or pitot tube), they are far more reliable and require less maintainence, resulting in lower life-cycle costs. This is largely due to the absence of moving parts. 

The meter applies Farraday's law to measure liquid flow. The sensor contains two C-shaped electrodes that produce a magnetic field when energized. When a conductive liquid passes through the magnetic field between the electrodes, a voltage is induced in a coiled wire. The voltage is proportional to the electric field strength, diameter of the pipe, and flow velocity. 

Meters are tested at the factory for a set pipe diameter. The meter range minimum zero gpm (gallons per minute) to the maximum of 1761.2 gpm (for an 8-inch diameter) are also determined by the pipe characteristics. The display electronics were remotely mounted using specified wiring supplied by the manufacturer. The meters were installed on both closed- and open-water systems.

A common problem with the installation of flow meters is that a bend in the pipe near the installation point will cause inaccurate readings due to non-laminar flow. Fortunately, a sufficiently long section of pipe was available to provide a laminar flow for each of the five meters installed. 

The flow meters have a variable percentage error, which is 0.5% at high flows (>262gpm for 8" pipe, >145gpm for 6" pipe, and > 37gpm for 3" pipe) and increases as flow decreases. For velocities slower than 1.5 ft/sec, the error is given by 0.82/velocity.