FT
-
3500 ELECTROMAGNETIC FLOW METER
ONICON Incorporated 727.447.6140 Page 56 onicon.com
IMPORTANT NOTE
Non-metallic pipes are more susceptible to electrical noise. Grounding rings installed upstream and downstream of
the meter location to reduce the electrical noise present in the pipe may be required for proper operation. Refer to
section 1.5.1 and section 3.1 of this manual for additional information on the use of grounding rings.
5.4.1 Earth Connections & Electrical Noise Reduction
Introduction
FT-3500 electromagnetic ow meters are designed to detect microvolt signal levels at the electrodes located on the sensor
head. These signals are generated as conductive uids ow through the magnetic eld generated by the meter. If enough
random electrical noise is present at the electrodes, it can interfere with the ow signal measurement. Care must be taken
during installation to minimize the eects of electrical noise on the ow meter.
Minimizing Electrical Noise
The most eective way to minimize the eects of electrical noise is to make sure that the pipe, the uid and the
ow meter body are all connected to earth ground. This accomplishes two important goals. First, it ensures that the pipe,
uid and ow meter are all at the same electrical potential. 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 ow meter earth cable 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. If necessary, a separate earth cable should be
connected to the metal pipe near the meter.
Earth Connections (stranded wire 14 - 18 AWG)
Best Earth grounding rod driven into the ground to the depth of the water table.
Earth wire connected directly to the building electrical service panel.
Worst Earth wire connection inside an electrical outlet near the meter.
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