ONICON F-3100 Series - Manual (Page 30)

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F-3100 Flow Meter Manual 06/14 - 0670-7
Page 30
3.3.3 Earth Connection
F-3100 Electromagnetic Flow Meters are designed to detect microvolt signal levels at the
electrodes located in the flow meter body. These signals are generated as conductive fluids flow
through the magnetic field generated by the meter. If enough random electrical noise is present at
the electrodes, it can interfere with the flow measurement. Care must be taken during installation
to minimize the effects of electrical noise on the flow meter.
The most effective way to minimize the effects of electrical noise is to make sure that the pipe,
fluid, flow meter body and flow meter transmitter are all connected to the same earth ground.
This accomplishes two important goals. First, it ensures that the pipe, fluid, flow meter body
and electronics are all at the same electrical potential, and second, it ensures that this electrical
potential is the same as earth ground.
In order to be certain that the meter is properly connected to earth, the flow meter body earth
connections (at the flanges or on the neck of wafer meters) and the transmitter earth connection
should be run directly to a known earth connection. The length of this earth cable should be as
short as practically possible, preferably ≤25 feet in length. The table below lists earth connections
from best to worst.
!
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IMPORTANT NOTE
Non-metallic pipes are more susceptible to electrical noise. Grounding rings installed upstream
and downstream of the flow meter body to reduce the electrical noise present in the pipe may be
required for proper operation.
CAUTION
Do not use bolts that hold pressure to make earth connections. Using flange bolts may result in poor
electrical connections due to the presence of paint and/or lubricants. Use the dedicated flange earth
connections or the dedicated earth connection on the neck of wafer style meters.
Earth Connections (stranded wire 14 - 18 AWG)
Best Earth grounding rod driven into the ground.
Earth wire connected directly to the building electrical service panel.
Worst Earth wire connection inside an electrical outlet near the meter.