Grounding Screw; Segment Compliance Voltage (See Figure 7); Cable Requirements; Intrinsically Safe Barriers - Flowserve Logix 3400MD User Instructions

NOTE: The Logix 3400MD positioner carries an intrinsically safe barrier
rating of 250 mA. Input currents should not exceed 250 mA, 5 watts.
6.2

Grounding Screw

The green grounding screw, located inside the termination cap, should
be used to provide the unit with an adequate and reliable earth ground
reference. This ground should be tied to the same ground as the
electrical conduit. Additionally, the electrical conduit should be earth
grounded at both ends of its run.
0 WARNING: The green grounding screw must not be used to
terminate signal shield wires.
6.3 Segment Compliance Voltage
Output compliance voltage refers to the voltage limit that can be
provided by the FF source. A FF system consists of the FF source,
wiring resistance, barrier resistance (if present), and the Logix 3400MD
positioner voltage. The Logix 3400MD digital positioner requires that
the system allows for a 9.0 VDC drop across the positioner at minimum
segment voltage. The actual voltage at the terminals varies from 9.0 to
32.0 VDC depending on the FF signal and ambient temperature.
Determine if the segment will support the Logix 3400MD digital
positioner by performing the following calculation.
Voltage = Compliance Voltage (@ 23 mA) –
23 mA • (R
barrier
The calculated voltage must be greater than 9 VDC in order to safely
support the Logix 3400MD digital positioner.
LEDs
14
(See Figure 7)
Equation 1
+ R )
wire
DIP Switch Block
Jog Buttons
Rotary
Selector
Switch
RE-CAL Button
Logix 3400MD Digital Positioner FCD LGENIM3404-00 – 9/09
Example:
DCS Compliance Voltage = 19 VDC
R = 300 Ω
barrier
R = 25 Ω
wire
Current = 23 mA
max
Voltage = 19 VDC – 0.023 A • (300 Ω + 25 Ω) = 11.5 VDC
The voltage 11.5 VDC is greater than the required 9.0 VDC; therefore,
this system will support the Logix 3400IQ digital positioner.
6.4

Cable Requirements

The Logix 3400MD digital positioner utilizes the FF protocol. This
communication signal is superimposed on the supply voltage.
FF rated cable should be used. Refer to H1 wiring specification.
6.5

Intrinsically Safe Barriers

When selecting an intrinsically safe barrier, make sure the barrier is
FF compatible. Although the barrier will pass the segment voltage and
allow normal positioner operation, if not compatible, it may prevent FF
communication.
6.6

DD Support

The DD for the Logix 3400MD can be downloaded from either the
flowserve website: www.valvesight.com or the F
website: www.Fieldbus.org.
7

Startup

Figure 8: Local User Interface
F
oundation ieldbus