1
3
2
-
+
+
-
SHIELD
Appendix F - Grounding schematic
To Hport Mux
(HART® interface)
PLC or DCS
4-20 mA output
Twisted shielded pair
SmartCal
positioner
Shield should be connected to
the shield termination point of
the output module or to the
power supply ground
Tape shield & drain
wire to prevent
contact with ground
Connection from DCS or PLC to positioner is 20 Gauge shielded twisted pair (Belden
8762 or equivalent). Maximum distance is 1500 m (5000 feet).
Connection from HART® Multiplexer to positioner is 20 Gauge shielded twisted pair
(Belden 8762 or equivalent). Maximum distance from HART® Multiplexer to positioner is
1800 m (6000 feet).
Shield shall be connected to ground at one point only in order to avoid ground loops and
noise interference.
The following table, per IEEE Std 518-1982, indicates the minimum distance between
cable trays and conduits containing Level 1 (this includes 4-20 mA signals) and 120 V AC
or 480 V AC, in order to minimize electrical noise interference.
1
2
3
4
Raceway
480 V AC
120 V AC
Tray
26”
6”
Tray-conduit
18”
4”
Conduit
12”
3”
page 33
AVID SmartCal valve positioner
Installation & operating instructions
O-ring
Sleeve
Spacer
O-ring
End plate
End plate
Spacer
Spring
Spool
Valve body
SPOOL/VALVE ASSY
PR-30034
