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3.5.2
Earth Connection
ISM 5.0 Insertion Magmeters are designed to detect microvolt signal levels at the
electrodes located on the sensor head. 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, the fluid and the flow meter body are all connected to earth ground. This
accomplishes two important goals. First, it ensures that the pipe, fluid and flow meter 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 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
Earth wire connected directly to the building electrical service panel.
Worst
Earth wire connection inside an electrical outlet near the meter.
IMPORTANT NOTE
Under certain circumstances, connecting the meter to earth through the green/yellow earth wire
may increase the amount of electrical noise present at the meter. Contact GREYLINE for
technical assistance if you experience increased noise levels with the earth wire connected to
earth.
i
CAUTION
Failure to provide a proper earth connection to the meter may result in excessive electrical
noise that will interfere with the operation of the meter.
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