Masoneilan Dresser
SVI II AP Quick Start Guide
12
Grounding Practices
To ensure proper grounding make sure that case, signal, and ground
connections are made in compliance with the plants normal grounding
practices. Any point in the loop can be referenced to ground, but there
must never be more than one ground point. Normally ground is
connected at the controller or at the intrinsic safety barrier.
The case grounding screws are located on the outside of the case at
the lower right of the display cover and inside the cover. The case is
isolated from all circuitry and can be grounded locally in accordance
with applicable codes.
If noise or instability is present set the positioner to MANUAL mode of
operation and manually position the valve over it’s entire range. If the
valve is stable in MANUAL mode then the problem can be noise in the
control system. Recheck all wiring connections and ground points.
Compliance Voltage in Single Drop Current Mode
The SVI II AP requires 9.0 Volts at 20 mA and 11.0 Volts at 4 mA.
Typical HART devices require MORE Voltage at higher current and
MORE current source have LESS Voltage available at higher current.
The SVI II AP is unique in that it requires LESS Voltage at higher current
which compliments the characteristic of the source requiring only
9
Volts at 20 mA
.
Verify Wiring and Connections
Note:
For split range installations the compliance voltage must be ca-
pable of the minimum span being 5 mA; the upper range value
must be 8 mA to 20 mA; the lower range values must be 4 mA
to 14 mA.
Use the following procedure to ensure that the SVI II AP is properly
powered:
Connect a DC voltmeter across the input terminals.
For an input current between 4 and 20 mA the
voltage varies between 11V and 9 V respective.
Current is read from the local display or with a
milliammeter installed in series the SVI II AP.
When voltage exceeds 11 V check that polarity is
correct.
If voltage is less than 9 V and polarity is correct,
voltage compliance of current source is inadequate.
Connect a milliammeter in series with the current
signal. Verify that source can supply 20 mA to SVI II
AP input.
If 20 mA is not attainable, troubleshoot the source
and set up.
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